WO2013162738A1

WO2013162738A1 - Siloxane compositions comprising siloxane-modified hydrogels

Info

Publication number: WO2013162738A1
Application number: PCT/US2013/031121
Authority: WO
Inventors: Dongchan Ahn; Robert O. Huber; Timothy Paul Mitchell; Gerald K. Schalau; James F. Thompson
Original assignee: Dow Corning Corporation
Priority date: 2012-04-27
Filing date: 2013-03-14
Publication date: 2013-10-31

Abstract

Provided in various embodiments are addition curable silicone compositions, methods for their preparation, and uses thereof for delivery of personal care and healthcare active ingredients, and agricultural active ingredients. In some embodiments, such addition curable silicone compositions comprise an addition curable organopolysiloxane, a hydrosilylation cure catalyst or initiator for the addition curing reaction, (c) a hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through either an amine-capping reaction or through a free radical-initiated encapsulation process utilizing an organoborane initiator. The silicone compositions optionally comprise or are optionally treated with one or more of at least one multifunctional crosslinker for the addition curable organopolysiloxane, at least one water-soluble active ingredient, and at least one surfactant. The hydrogel or hydrogel microparticle includes at least one siloxane-coated surface. The silicone compositions are hydrosilylation curable silicone compositions.

Description

SILOXANE COMPOSITIONS COMPRISING SILOXANE-MODIFIED HYDROGELS

BACKGROUND OF THE INVENTION

[0001] Curable silicone compositions are useful in various applications. Hydrogel-silicone compositions, for example, may be useful for encapsulating and deliverying pharmaceutical agents, vitamins, fragrances, oils, and other compounds in personal care and healthcare applications. For example, hydrogel-silicone compositions are particularly useful for life science applications in which water or water-soluble actives are sought to be carried in a crosslinkable silicone matrix, such as wound care adhesives and cosmetics. These materials have been shown to be tunable by pH from water-dispersible to water-immiscible and offer new possibilities for the use of silicones in aqueous systems. The selective absorption and desorption of water and water-borne agents suggest that these materials can be useful for harvesting, transporting, purifying and delivering water. The increased absorption of water in these materials is contemplated to facilitate the management of fluids and wound exudates in topical skin and wound care applications. The cured products of these hydrosilylation curable silicone elastomer compositions may have varied physical forms especially silicone tacky gels, pressure sensitive adhesives, liquid silicone rubbers, high consistency elastomers, silicone adhesives, silicone sealants, and silicone encapsulants.

[0002] Although various methods of preparing hydrogel-silicone compositions are known, there remains a need for methods of readily preparing such compositions for use in a variety of applications.

SUMMARY OF THE INVENTION

[0003] These needs are met by the present invention, which in various embodiments provide addition curable silicone compositions, methods for their preparation, and uses thereof for varied end uses such as delivery of personal care and healthcare active ingredients as well as agricultural active ingredients. The addition curable silicone compositions comprise (a) an addition curable organopolysiloxane (b) a cure catalyst or initiator for the addition curing reaction, (c) a hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through either an amine capping reaction or through a free radical-initiated encapsulation process utilizing an organoborane initiator, and optionally (d) a multifunctional crosslinker for the addition curable organopolysiloxane and further optionally (e) a water-soluble active ingredient and further optionally (f) at least one surfactant. The silicone compositions are hydrosilylation curable silicone compositions. [0004] These and additional features and advantages of the invention will become apparent in the course of the following detailed description.

DETAILED DESCRIPTION

[0005] Features and advantages of the invention will now be described with occasional reference to specific embodiments. However, the invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0006] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0007] Unless otherwise specifically indicated, the term "water-compatible" as used herein is intended to mean at least partially soluble in water, but when used to describe a cross-linked polymer, the term is intended to mean that the polymer is able to absorb water.

[0008] As used herein, the term "hydrogel" is intended to refer to gels in which the cross- linked polymer matrix is fully or partially swollen with water, one or more water-compatible alcohols, or combinations thereof. Accordingly, the term also includes, but is not limited to, alcogels fully or partially swollen with a water-compatible alcohol. The crosslinking of the polymer matrix may be chemical or physical in nature. As non-limiting examples, the hydrogel may be crosslinked through covalent bonds, ionic interactions, hydrogen bonding, chain entanglement, or self-association of microphase segregating moieties. Additionally, it is to be understood that such hydrogels may exist and be used in a dehydrated (unswollen) state.

[0009] Unless otherwise specifically indicated, the term "hydrogel microparticle" as used herein is intended to refer to both a polymeric microparticle and a polymeric microparticle that is swollen with a sufficiently compatible fluid.

[0010] As used herein, the term "alcohol" is intended to refer to water-compatible alcohols. Accordingly, the term "alcohol-compatible organic polymer" is intended to refer to an organic polymer that is compatible with a water-compatible alcohol.

[0011] As used herein, the term "hydrophobic" is intended to mean lacking an affinity for and/or being resistant to water and/or water-compatible compounds. Accordingly, the term also refers to lacking an affinity for and/or being resistant to water-compatible alcohols. [0012] As used herein, the term "paste" is intended to mean a suspension of hydrogel microparticles in a fluid.

[0013] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from error found in their respective measurements.

[0014] In various embodiments, provided are addition curable silicone compositions which comprise (a) an addition curable, unsaturated organopolysiloxane (referred to herein as Component A), (b) a hydrosilylation cure catalyst or initiator for the addition curing reaction (referred to herein as Component B), (c) a hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through either an amine-capping reaction or through a free radical-initiated encapsulation process utilizing an organoborane initiator (referred to herein as Component C). The silicone compositions optionally comprise or are optionally treated with one or more of (d) at least one multifunctional crosslinker for the addition curable organopolysiloxane (referred to herein as Component D) and further optionally (e) at least one water-soluble active ingredient (referred to herein as Component E) and further optionally (f) at least one surfactant (referred to herein as Component F). The hydrogel or hydrogel microparticle of Component C includes at least one siloxane-coated surface. The at least one multifunctional crosslinker of Component D is at least one SiH functional organopolysiloxane. The silicone compositions are hydrosilylation curable silicone compositions. The addition curable silicone compositions act as barriers for the migration of water and water-compatible compounds.

[0015] In various embodiments described herein, provided are methods for the preparation of addition curable silicone compositions and uses thereof. The hydrogel-silicone compositions described herein are useful as delivery of personal care and healthcare and agricultural active ingredients. The siloxane coatings on the exposed surfaces or near- surface regions of the hydrogel-silicone compositions described herein allow for modulation of rates of transport of water and water-compatible components across the coatings.

Component A, Unsaturated Organopolysiloxane

[0016] The silicone compositions in their pre-cured state include an unsaturated organopolysiloxane (Component A). The unsaturated organopolysiloxane is an addition curable organopolysiloxane. The organopolysiloxane compound of Component A has an average of at least two silicon-bonded alkenyl groups per molecule. The organopolysiloxane can be present in an amount sufficient to allow curing of the silicone composition. The amount of Component A present in the silicone compositions may vary, but in some embodiments ranges from about 40% to about 95% (by weight), alternatively from about 32% to about 97% (by weight), alternatively from about 15% to about 99% (by weight), based on the amount by total weight of components in the composition.

[0017] The organopolysiloxane compound of Component A contains an average of at least two silicon-bonded alkenyl groups per molecule, alternatively at least three silicon-bonded alkenyl groups per molecule. It is generally understood that cross-linking occurs when the sum of the average number of silicon-bonded hydrogen atoms per molecule in the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule and the average number of silicon-bonded alkenyl groups per molecule in the organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule is equal to or greater than four.

[0018] The organopolysiloxane compound of Component A has an average of at least two unsaturated organic groups per molecule can have a linear or branched structure. The organopolysiloxane compound can be a homopolymer or a copolymer. The organopolysiloxane compound can be a disiloxane, trisiloxane, or polysiloxane. The structure of the organopolysiloxane compound can be linear, branched, cyclic, or resinous. Cyclosiloxanes can have from 3 to 12 silicon atoms, alternatively from 3 to 10 silicon atoms, alternatively from 3 to 5 silicon atoms. In acyclic organopolysiloxanes, the silicon-bonded alkenyl groups can be located at terminal, pendant, or at both terminal and pendant positions.

[0019] The unsaturated organic groups can be alkenyl groups having from 2 to 12 carbon atoms and are exemplified by, but not limited to, vinyl, allyl, butenyl, and hexenyl. The unsaturated organic groups can be alkynyl groups having 2 to 12 carbon atoms, and are exemplified by, but not limited to, ethynyl, propynyl, and butynyl. Alternatively, the unsaturated organic groups can contain acrylate-functional or methacrylate-functional groups and are exemplified by, but not limited to, acryloyloxyalkyl such as acryloyloxypropyl and methacryloyloxyalkyl such as methacryloyloxypropyl. The unsaturated organic groups in the organopolysiloxane compound can be located at terminal, pendant, or both terminal and pendant positions.

[0020] The remaining silicon-bonded organic groups in the organopolysiloxane compound can be monovalent organic groups free of aliphatic unsaturation. The monovalent organic groups can have 1 to 20 carbon atoms, alternatively 1 to 10 carbon atoms, and are exemplified by, but not limited to alkyl groups, aromatic groups, cyano-functional groups exemplified by cyanoalkyl groups, halogenated hydrocarbon groups, aminoalkyl groups, hindered aminoalkyl groups, epoxyalkyl groups, ester functional groups, hydroxyl functional groups, isocyanate and masked isocyanate functional groups, aldehyde functional groups, anhydride functional groups, carboxylic acid functional groups, and metal salts of carboxylic acids.

[0021] The organopolysiloxane compound of Component A can have a viscosity of 0.05 to 500 Pa-s at 25°C, alternatively 0.1 to 200 Pa-s at 25°C. The organopolysiloxane compound of Component A has an average of at least two silicon-bonded alkenyl groups per molecule can include a polyorganosiloxane of the formula

(a) R¹ ₃SiO(R¹ ₂SiO)_a(R¹R²SiO)pSiR¹ ₃,

(b) R³ ₂R⁴SiO(R³2SiO)_¾(R³R⁴SiO)gSiR³ ₂R⁴, or

(c) a combination thereof.

In formula (a), a has an average value of 0 to 2000, and β has an average value of 2 to 2000. Each R¹ is independently a monovalent organic group. Suitable monovalent organic groups include, but are not limited to, acrylic functional groups, alkyl groups, halogenated hydrocarbon groups, alkenyl groups, alkynyl groups, aromatic groups, and cyanoalkyl groups. Each R² is independently an unsaturated monovalent organic group. R² is exemplified by alkenyl groups, alkynyl groups, and acrylic functional groups.

[0022] In formula (b), χ has an average value of 0 to 2000, and δ has an average value of 0 to 2000. Each R³ is independently a monovalent organic group. Suitable monovalent organic groups include, but are not limited to, acrylic functional groups, alkyl groups, halogenated hydrocarbon groups, alkenyl groups, alkynyl groups, aromatic groups, and cyanoalkyl groups. Each R⁴ is independently an unsaturated organic hydrocarbon group. R⁴ is exemplified by alkenyl groups, alkynyl groups, and acrylic functional groups.

[0023] The organopolysiloxane compound of Component A can include polydiorganosiloxanes such as dimethylvinylsiloxy-terminated polydimethylsiloxane, dimethylvinylsiloxy-terminated poly(dimethylsiloxane/methylvinylsiloxane), dimethylvinylsiloxy-terminated polymethylvinylsiloxane, trimethylsiloxy-terminated poly(dimethylsiloxane/methylvinylsiloxane), trimethylsiloxy-terminated polymethylvinylsiloxane, dimethylvinylsiloxy-terminated poly(dimethylsiloxane/methylphenylsiloxane), dimethylvinylsiloxy-terminated poly(dimethylsiloxane/diphenylsiloxane), phenyl, methyl, vinyl-siloxy-terminated polydimethylsiloxane, dimethyl-acryloyloxypropyl-siloxy-terminated polydimethylsiloxane, dimethyl-methacryloyloxypropyl-siloxy-terminated polydimethylsiloxane, dimethylhexenylsiloxy-terminated polydimethylsiloxane, dimethylhexenylsiloxy-terminated poly(dimethylsiloxane/methylhexenylsiloxane), dimethylhexenylsiloxy-terminated polymethylhexenylsiloxane, trimethylsiloxy-terminated poly(dimethylsiloxane/methylhexenylsiloxane), dimethylvinylsiloxy-terminated poly(dimethylsiloxane/methylcyanopropylsiloxane), dimethylvinylsiloxy-terminated polymethyl3,3,3-trifluoropropyl siloxane, dimethylvinylsiloxy-terminated poly(methyl- 6,6,6,5,5,4,4,3,3-nonafluorohexylsiloxane), dimethylvinylsiloxy-terminated poly(methyl3,3,3- trifluoropropyl siloxane/dimethylsiloxane), dimethylvinylsiloxy-terminated poly(methyl- 6,6,6,5,5,4,4,3,3-nonafluorohexylsiloxane/dimethylsiloxane), a resin consisting essentially of (CH₃)₃SiOi/2 units, (Vinyl)(CH₃)₂SiOi/2 and Si0₄/₂ units, and combinations thereof.

[0024] Methods of preparing organopolysiloxane compounds suitable for use as the organopolysiloxane of Component A having an average of at least two silicon-bonded alkenyl groups per molecule, such as hydrolysis and condensation of the corresponding organohalosilanes or equilibration of cyclic polydiorganosiloxanes, are well known in the art.

[0025] The organopolysiloxane compound of Component A may further include resins such as an MQ resin consisting essentially of R⁵ ₃Si0_1/2 units and Si0_4/2 units, a TD resin consisting essentially of R⁵Si0_3/2 units and R⁵ ₂Si0₂/2 units, an MT resin consisting essentially of R⁵ ₃Si0_1/2 units and R⁵Si0_3/2 units, an MTD resin consisting essentially of R⁵ ₃Si0_1/2 units, R⁵Si0_3/2 units, and R⁵ ₂Si0_2/2 units, or a combination thereof.

[0026] Each R⁵ is a monovalent organic group. The monovalent organic groups represented by R⁵ may have 1 to 20 carbon atoms, alternatively 1 to 10 carbon atoms. Examples of monovalent organic groups include, but are not limited to, acrylate functional groups such as acryloxyalkyl groups, methacrylate functional groups such as methacryloxyalkyl groups, cyano-functional groups, and monovalent hydrocarbon groups. Monovalent hydrocarbon groups include, but are not limited to, alkyl such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl; halogenated hydrocarbon groups such as 6,6,6,5,5,4,4,3,3-nonafluorohexyl, 4,4,4,3,3-pentafluorobutyl, 5,5,5,4,4,3,3-heptafluoropentyl, 3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl; cycloalkyl such as cyclohexyl; alkenyl such as vinyl, allyl, butenyl, and hexenyl; alkynyl such as ethynyl, propynyl, and butynyl; and aryl such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl. Cyano-functional groups include, but are not limited to cyanoalkyl groups such as cyanoethyl and cyanopropyl.

[0027] The resin may contain an average of about 3 to about 30 mole percent of unsaturated organic groups. The unsaturated organic groups may be alkenyl groups, alkynyl groups, acrylate-functional groups, methacrylate-functional groups, or combinations thereof. The mole percent of unsaturated organic groups in the resin is the ratio of the number of moles of unsaturated group-containing siloxane units in the resin to the total number of moles of siloxane units in the resin, multiplied by 100.

[0028] Methods of preparing resins are well known in the art. For example, resins may be prepared by treating a resin copolymer produced by a silica hydrosol capping process with at least an alkenyl-containing end-blocking reagent. In one such process, a silica hydrosol is reacted under acidic conditions with a hydrolyzable triorganosilane such as trimethylchlorosilane, a siloxane such as hexamethyldisiloxane, or mixtures thereof, and a copolymer having M and Q units is recovered; the resulting copolymers generally contain from 2 to 5 percent by weight of hydroxyl groups. In this process, the resulting copolymers may be reacted with an unsaturated organic group-containing endblocking agent and an endblocking agent free of aliphatic unsaturation, in an amount sufficient to provide from 3 to 30 mole percent of unsaturated organic groups in the final resin product.

[0029] The organopolysiloxane compound of Component A can be a single polyorganosiloxane or a combination including two or more polyorganosiloxanes that differ in at least one of the following properties: structure, viscosity, average molecular weight, siloxane units, and sequence.

[0030] Examples of organopolysiloxanes having an average of at least two silicon-bonded alkenyl groups per molecule can include compounds having the average unit formula (d)

(R¹R⁴R⁵Si0_1/2)_w(R¹ ₂Si0_2/2)_x(R⁴Si0₃/2)y(Si04/₂)z

wherein R¹ is an organic group independently selected from any optionally further substituted C_1-15 organic group, including C_1-15 monovalent aliphatic hydrocarbon groups, C_4- ₁₅ monovalent aromatic hydrocarbon groups, and monovalent epoxy-substituted organic groups, R⁴ is C₂ to C₄ alkenyl, R⁵ is R¹ or R⁴, 0<w<0.95, 0<x<1 , 0<y<1 , 0<z<0.95, and w+x+y+z«1. In some embodiments, R¹ is C-i to C₁₀ hydrocarbyl or C-i to C₁₀ halogen- substituted hydrocarbyl, both free of aliphatic unsaturation, or C₄ to Ci₄ aryl. The hydrocarbyl and halogen-substituted hydrocarbyl groups represented by R¹ are as described and exemplified herein. In some embodiments, w is from 0.01 to 0.6, x is from 0 to 0.5, y is from 0 to 0.95, z is from 0 to 0.4, and w+x+y+z«1.

[0031] Examples of suitable organopolysiloxanes of average unit formula (d) include, but are not limited to, siloxanes having the following formulae: PhSi(OSiMe₂Vi)₃, Si(OSiMe₂Vi)₄, MeSi(OSiMe₂Vi)₃, and Ph₂Si(OSiMe₂Vi)₂, where Me is methyl, Ph is phenyl, and Vi is vinyl. An example includes a dimethylvinylsiloxy-terminated polydimethylsiloxane; in some examples, this organopolysiloxane has a viscosity of about 55 Pa-s at 25° C. Another example includes an organopolysiloxane resin including CH₂=CH(CH₃)₂Si0_1/2 units, (CH₃)₃Si0_1/2 units, and Si0_4/2 units, wherein the mole ratio of CH₂=CH(CH₃)₂Si0_1/2units and (CH₃)₃SiOi_/2 units combined to Si0_4/2 units is about 0.7; in some examples the resin has weight-average molecular weight of about 22,000, a polydispersity of about 5, and contains about 1.8% by weight (about 5.5 mole %) of vinyl groups. An example includes dimethylvinylsiloxy-terminated poly(trifluoropropyl-methyl)siloxane; in some examples, this organopolysiloxane has a viscosity of about 50 Pa-s at 25°C.

[0032] In some examples, the organopolysiloxane having an average of at least two silicon- bonded alkenyl groups per molecule is a resin, wherein the silicone resin includes R¹ ₂R² SiOi/2 siloxane units and Si0_4/2 siloxane units, wherein each R¹ is independently selected from monovalent hydrocarbon and monovalent halogenated hydrocarbon groups, both free of aliphatic unsaturation, R² is R¹ or alkenyl, the mass ratio of R¹ ₂R² SiOi_/2 units to Si0_4/2 units is from about 4:1 to about 2.3:1 , and the resin contains an average of from about 0.33 to about 0.45 mass percent of alkenyl groups.

[0033] The organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule can be a single organopolysiloxane compound or a mixture including two or more different organopolysiloxane compounds, each as described above. For example the organopolysiloxane can include a single organopolysiloxane, or a mixture of two different organopolysiloxanes.

[0034] Methods of preparing organopolysiloxanes containing silicon-bonded alkenyl groups are well known in the art; many of these compounds are commercially available.

[0035] In descriptions of average unit formula, such as formula (d), the subscripts w, x, y, and z are mole fractions. It is appreciated that those of skill in the art understand that for the average unit formula (d), the variables R¹, R², R³, R⁴, R⁵, and R⁶ can independently vary between individual siloxane units. Alternatively, the variables R¹, R², R³, R⁴, R⁵, and R⁶ can independently be the same between individual siloxane units. For example, average unit formula (d)

(R¹R⁴R⁵Si0_1/2)_w(R¹ ₂Si0_2/2)_x(R⁴Si0_3/2)_y(Si0_4/2)_z

can include the following average unit formula:

(R¹R⁴R⁵Si0_1/2)_w(R^1a ₂Si0_2/2)_x1(R^1b ₂Si0_2/2)_x2(R⁴Si0_3/2)_y(Si0_4/2)_z

where subscripts x1 +x2 = x, and where R^1a is not equal to R^1b. Alternatively, R^1a can be equal to R^1b.

[0036] Similarly, for example, average unit formula (e) can include the following average unit formula:

(R¹R⁴R⁵Si0_1/2)_w(R¹ ₂Si0_2/2)_x(R^4aSi0_3/2)_yi(R^4bSi0_3/2)_y2(Si0_4/2)_z

where subscripts y1 +y2 = y, and where R^4a is not equal to R^4b. Alternatively, R^4a is equal to

R^4b.

[0037] In the uncured composition, the concentration of alkenyl groups, including those from the organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule, can be sufficient to cure (e.g. cross-link) the silicone composition. The exact amount of the alkenyl groups depends on the desired extent of cure, which generally increases as the ratio of the number of moles of alkenyl groups to the number of moles of silicon-bonded hydrogen atoms in the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule increases. In some embodiments, in the pre-cured composition, the molar ratio of silicon-bonded hydrogen atoms to the total number of alkenyl groups (including those from silicon-bonded alkenyl groups, polyethers with at least one alkenyl group, cure modifiers, or any other compound that includes an alkenyl group) can be, for example, about 0.3:1 to about 5:1 , about 0.5:1 to about 3:1 , about 0.8:1 to about 2:1 , about 0.9:1 to about 1.8:1 , or 1 :1 to about 1.5:1.

Component B, Hydrosilylation Catalyst

[0038] The silicone compositions in their pre-cured state include at least one hydrosilylation catalyst (Component B). The hydrosilylation catalyst is a cure catalyst or initiator for the addition curing reaction. During curing of the silicone composition, the hydrosilylation catalyst can catalyze an addition reaction (hydrosilylation) of the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule with the organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule. In some embodiments, the hydrosilylation catalyst can be any hydrosilylation catalyst including a platinum group metal or a compound containing a platinum group metal. Platinum group metals include platinum, rhodium, ruthenium, palladium, osmium and iridium. Typically, the platinum group metal is platinum, based on its high activity in hydrosilylation reactions.

[0039] Nonlimiting examples of hydrosilylation catalysts include the complexes of chloroplatinic acid and certain vinyl-containing organosiloxanes, microencapsulated hydrosilylation catalysts including a platinum group metal encapsulated in a thermoplastic resin, and photoactivated hydrosilylation catalysts.

[0040] An example of a suitable hydrosilylation catalyst includes a platinum(IV) complex of 1 ,3-diethenyl-1 ,1 ,3,3-tetramethyldisiloxane. In some examples, the catalyst can include a mixture of a platinum(IV) complex of 1 ,3-diethenyl-1 ,1 ,3,3-tetramethyldisiloxane, dimethylvinylsiloxy-terminated polydimethylsiloxane, and tetramethyldivinyldisiloxane. In some examples, the dimethylvinylsiloxy-terminated polydimethylsiloxane can have a viscosity of about 0.45 Pa-s at 25° C. In some examples, the catalyst can include a mixture of about 1 % of a platinum(IV) complex of 1 ,3-diethenyl-1 ,1 ,3,3-tetramethyldisiloxane, about 92% of dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 0.45 Pa-s at 25° C, and about 7% of tetramethyldivinyldisiloxane. In some other examples, the catalyst can include a mixture of about 2% of a platinum(IV) complex of 1 ,3-diethenyl- 1 ,1 ,3,3-tetramethyldisiloxane, 92% of dimethylvinylsiloxy-terminated poly(trifluoropropyl- methyl) siloxane, and 6% of tetramethyldivinyldisiloxane.

[0041] The concentration of Component B present in the silicone compositions can be sufficient to catalyze the addition reaction (hydrosilylation) of the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule with the organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule. Typically, the concentration of the hydrosilylation catalyst is sufficient to provide from about 0.1 to about 1000 ppm of a platinum group metal, from about 0.5 to about 500 ppm of a platinum group metal, and more preferably from about 1 to about 100 ppm of a platinum group metal, based on the total weight of the uncured composition.

Component C, Siloxane Surface-Modified Hydrogels and Hydrogel Microparticles

[0042] The silicone compositions in their pre-cured state include at least one surface- modified hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through either an amine-capping reaction or through a free- radical initiated encapsulation process utilizing an organoborane initiator to form at least one siloxane-coated surface on the hydrogel or the hydrogel microparticle (Component C). The hydrogel or hydrogel microparticles used in the amine-capping reaction process or the free- radical initiated encapsulation process are selected from at least one water-compatible organic polymer, alcohol-compatible organic polymer, and combinations thereof. The polymer may be homopolymeric, heteropolymeric (including, but not limited to, cross- polymers or co-polymers of any co-monomer distribution), and may be linear, branched, hyperbranched, dendrimeric, or crosslinked to any extent.

[0043] The hydrogel microparticles used for the provided methods may have any shape (i.e., spherical or irregular) or size. The microparticles used may be formed directly or from the shearing or pulverizing of a gel monolith. Non-limiting examples of suitably sized microparticles include those having an average particle size of from about 0.1 μηη to about 100μηι.

[0044] The surface-modified hydrogels and hydrogel microparticles of the provided methods may be dried and pulverized to form a powder. Such powders can be used in agricultural products or personal care and healthcare products, and since the powders can be formed from hydrogel compositions comprising active ingredients, the powders are ideal for delivering active ingredients in such products.

[0045] The surface-modified hydrogels and microparticles prepared by the provided methods may also be used to form pastes. Typically, a paste can be formed by applying high shear, cutting, abrasion, or impact to the hydrogel at any temperature, including sub- ambient conditions, either as it is being formed or after it is formed, preferably in the presence of a non-reactive diluent. A paste can also be formed by dispersing microparticles in a non-reactive diluent. Pastes made from the surface-modified hydrogel compositions and microparticles are stable and can have a wide range of viscosities, thereby making them particularly useful as bases for agricultural or personal care and healthcare products. The diluent chosen will, in some embodiments, depend upon the thickness of the siloxane coating formed on the hydrogels or the hydrogel microparticles. Nonlimiting examples of suitable diluents include water, water compatible alcohols, water-immiscible silicones, diols, polyols, organic solvents, organic oils, supercriticial fluids, "ecologically-friendly" solvents, organosiloxane fluids, and combinations thereof.

Component C, Alternative Embodiment A: Amine-Capping Reaction

[0046] The hydrogel or hydrogel microparticles used in the amine-capping reaction process of Alternative Embodiment A may be selected from a carboxy-functional organic polymer, an anhydride-functional organic polymer, and an epoxy-functional organic polymer. Examples of suitable polymers for the hydrogel or hydrogel microparticles used in the amine-capping reaction process of Alternative Embodiment A include, but are not limited to, polyacrylic acid, polymethacrylic acid, salts of polyacrylic acid, salts of polymethacrylic acid, poly(2- hydroxyethyl methacrylate), polylactic acid, polyglycolic acid, polyanhydrides such as poly(methacrylic) anhydride, poly(acrylic) anhydride, polysebacic anhydride, hyaluronic acid- containing polymers and copolymers such as poly(hyaluronic acid), and hyaluronic acid containing polymers and copolymers, and combinations thereof. The polymers may also be copolymers comprised of water-compatible monomeric units and amine-reactive monomeric units, such as a poly(ethylhexylmethacrylate)-polyacrylic acid copolymer, or a polyvinylalcohol-polyacrylic acid copolymer. The polymers may also be partially crosslinked polyacrylic acid homopolymers, ionomers and copolymers such as CARBOPOL® ETD 2020, CARBOPOL® Ultrez 20, and CARBOPOL® ETD 2050, available from The Lubrizol Corporation, Wickliffe, Ohio. One of skill in the art will appreciate that the methods and compositions described herein are not limited to such gels and microparticles.

[0047] The hydrogel or hydrogel microparticles that are selected for use in the amine- capping reaction process of Alternative Embodiment A may include amine-reactive groups selected from carboxy-functional groups, sulfonic acid-functional groups, epoxy groups, or combinations thereof. The hydrogel or hydrogel microparticles that are selected for use in Alternative Embodiment A may include at least one organic polymer comprising amine- reactive groups selected from carboxy-functional groups, sulfonic acid-functional groups, epoxy groups, and combinations thereof. In some embodiments, the hydrogel or hydrogel microparticles used in the amine-capping reaction process of Alternative Embodiment A have at least 5 mol % of amine-reactive groups. In other embodiments, the hydrogel or hydrogel microparticles have from about 5 mol % to about 10 mol % of amine-reactive groups; in further embodiments, the hydrogel or hydrogel microparticles have at least 10 mol % of amine-reactive groups.

[0048] The amount of Component C present in the silicone compositions of Alternative Embodiment A may vary, but in some embodiments ranges from about 2.5% to about 16% (by weight), alternatively from about 1 % to about 30% (by weight), alternatively from about 0.5% to about 50% (by weight), based on the amount by total weight of components in the composition.

Preparation of Component C, the Siloxane Surface-Modified Hydrogels and

Hydrogel Microparticles of Alternative Embodiment A

[0049] Further details about the methods of creating the siloxane surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment A may be found in U.S. Provisional Patent Application US/61/305859 (DC 1091 1 ) filed on February 18, 2010 which is hereby incorporated herein by reference in its entirety.

[0050] Various materials are used in the production of the siloxane surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment A. The siloxane surface- modified hydrogels and siloxane surface-modified hydrogel microparticles of Alternative Embodiment A may be prepared by treating or mixing the above-described hydrogels or hydrogel microparticles with at least one amino-functional organosilicon compound to form at least one siloxane-coated surface on the hydrogel or hydrogel microparticles. The hydrogel or hydrogel microparticles comprise or are treated in the presence of at least one absorbable solvent selected from water, water-compatible alcohols, and combinations thereof. Nonlimiting suitable solvents include water-immiscible silicones; organic compounds; and "ecologically-friendly" solvents, such as ionic liquids and supercritical fluids; and mixtures thereof.

[0051] The amine functional organosilicon compounds may be linear, cyclic, branched, hyperbranched or resinous. The organosilicon compounds may comprise one or more siloxane linear polymers, siloxane branched polymers or siloxane resins having structural units of or anopolysiloxanes independently selected from:

(M) (T) (Q) wherein M represents a monofunctional unit R₃Si0_1/2; D represents a difunctional unit R2S1O2/2; represents a trifunctional unit RSi0_3/2; and Q represents a tetrafunctional unit S1O4/2, where "R" represents any suitable functional group.

[0052] The organosilicon compounds may comprise a linear siloxane polymer comprising combinations of units selected from M, D, R⁵ ₃Si0_1/2 units, and R⁵ ₂SiC>2/2 units. The organosilicon compound may further comprise a branched polymer comprising combinations of units selected from M, D, T, R⁵ ₃SiOi_/2 units, R⁵ ₂SiC>2/2 units, and R⁵Si0_3/2 units. The organosilicon compounds may comprise a siloxane resin selected from MQ resins having R⁵ ₃SiOi/2 units and Si0_4/2 units; TD resins having R⁵Si0_3/2 units and R⁵ ₂Si0_2/2 units; MT resins having R⁵ ₃SiOi_/2 units and R⁵Si0_3/2 units; MTD resins having R⁵ ₃SiOi_/2 units, R⁵Si0_3/2 units, and R⁵ ₂Si0_2/2 units, and combinations thereof; wherein each R⁵ group is independently a monovalent organic group having from 1-20 carbon atoms and may be an amine- containing group.

[0053] One or more active ingredients may be used in the production of the siloxane surface-modified hydrogels and hydrogel microparticles described herein. The least one active ingredient may be selected from personal care or healthcare active ingredients or from agricultural active ingredients as detailed below. The active ingredient may be added during the making of the hydrogel or hydrogel microparticle (pre-load method), added after formation of the hydrogel or hydrogel microparticle (post-load method), or added after formation of the surface-modified hydrogel or hydrogel microparticle (post-modification method).

Component C, Alternative Embodiment B: Free-Radical Initiated Encapsulation

[0054] Examples of suitable polymers for the hydrogel or hydrogel microparticles used in the free-radical initiated encapsulation process of Alternative Embodiment B include, but are not limited to, gelatin, methylcellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, polyethylene oxide, polyacrylamides, polyacrylic acid, polymethacrylic acid, salts of polyacrylic acid, salts of polymethacrylic acid, poly(2-hydroxyethyl methacrylate), polylactic acid, polyglycolic acid, polyvinylalcohol, polyanhydrides such as poly(methacrylic) anhydride, poly(acrylic) anhydride, polysebacic anhydride, collagen, hyaluronic acid- containing polymers and copolymers such as poly(hyaluronic acid), polypeptides, dextran, dextran sulfate, chitosan, chitin, agarose gels, fibrin gels, soy-derived hydrogels and alginate-based hydrogels such as poly(sodium alginate), and combinations thereof. The polymers may also be partially crosslinked polyacrylic acid homopolymers, ionomers and copolymers such as CARBOPOL® ETD 2020, CARBOPOL® Ultrez 20, and CARBOPOL® ETD 2050, available from The Lubrizol Corporation, Wickliffe, Ohio. One of skill in the art will appreciate that the methods and compositions described herein are not limited to such gels and microparticles.

[0055] In Alternative Embodiment B, the surface of the hydrogels or hydrogel microparticles is modified to create siloxane surface-modified hydrogels or siloxane surface-modified hydrogel microparticles. The siloxane surface-modified hydrogels and siloxane surface- modified hydrogel microparticles have surfaces that have been modified by an organopolysiloxane or silane through a free-radical initiated encapsulation process utilizing an organoborane initiator.

[0056] In Alternative Embodiment B, the siloxane surface-modified hydrogels and siloxane surface-modified hydrogel microparticles have surfaces that have been modified by the reaction of an acrylate-functional organopolysiloxane such as a methacrylate-functional organopolysiloxane.

[0057] The amount of Component C present in the silicone compositions of Alternative Embodiment B may vary, but in some embodiments ranges from about 2.5% to about 16% (by weight), alternatively from about 1 % to about 30% (by weight), alternatively from about 0.5% to about 50% (by weight), based on the amount by total weight of components in the composition.

Preparation of Component C, the Siloxane Surface-Modified Hydrogels and

Hydrogel Microparticles of Alternative Embodiment B

[0058] Further details about the methods of creating the siloxane surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment B may be found in U.S. Provisional Patent Application US/61/305863 (DC 10910) filed on February 18, 2010 which is hereby incorporated herein by reference in its entirety.

[0059] Various materials are used in the production of the siloxane surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment B. The siloxane surface- modified hydrogels and siloxane surface-modified hydrogel microparticles of Alternative Embodiment B may be prepared by treating or mixing the above-described hydrogels or hydrogel microparticles in the presence of oxygen with (i) at least one free-radical polymerizable compound that is immiscible with water, water-compatible alcohols, or combinations thereof and (ii) at least one organoborane free-radical initiator to form at least one siloxane-coated surface on the hydrogel or hydrogel microparticles. The at least one organoborane free-radical initiator may be selected from triethylborane-propanediamine, triethylborane-butylimidazole, triethylborane-methoxypropylamine, tri-n-butyl borane- methoxypropylamine, triethylborane-aminosilane, triethylborane-aminosiloxane complexes and complexes thereof. The hydrogel or hydrogel microparticles comprise or are treated in the presence of at least one absorbable solvent selected from water, water-compatible alcohols, diols, polyols, and combinations thereof. [0060] The at least one free-radical polymerizable compound(s) may be organic monomers, organic oligomers, organic polymers, organic compounds, organopolysiloxanes, and combinations thereof. The at least one free-radical polymerizable compound may be treated in the presence of a suitable solvent. Nonlimiting suitable solvents include water-immiscible solvents such as silicones, organic compounds, and "ecologically-friendly" solvents.

[0061] Where the at least one free-radical polymerizable compound is an organopolysiloxanes, the organopolysiloxane may be linear, branched, hyperbranched, or resinous in structure and the organopolysiloxane may have at least two free-radical polymerizable moieties per molecule. Thus, the at least one free-radical polymerizable compound can be a mixture of organopolysiloxanes differing in their degree of functionality and/or the nature of the free-radical polymerizable moieties. For example, the organopolysiloxane can be a fluid, a solid, or a solid that becomes flowable at an elevated temperature or by the application of shear. The organopolysiloxanes may also have a glass transition temperature or, upon polymerization or crosslinking, form particles that have a glass transition temperature, wherein the resulting silicone composition undergoes marked changes in its viscosity under the temperatures of use. Such compositions are particularly useful for encapsulation of active ingredients that are released by the introduction of heat.

[0062] In some embodiments, the at least one free-radical polymerizable compound may comprise an organosilicon compound. The organosilicon compounds may be linear, cyclic, branched, hyperbranched or resinous. In some embodiments, the at least one free-radical polymerizable compound may comprise one or more siloxane linear polymers, siloxane branched polymers or resins having structural units of organopolysiloxanes independently selected from:

CM) (D) (T) (Q)

wherein M represents a monofunctional unit R₃SiOi_/2; D represents a difunctional unit R2S1O2/2; T represents a trifunctional unit RSi0₃/₂; and Q represents a tetrafunctional unit S1O4/2. In some embodiments, the at least one free-radical polymerizable compound may comprise a siloxane resin selected from MQ resins having R⁵ ₃Si0_1/2 units and Si0_4/2 units; TD resins having R⁵Si0_3/2 units and R⁵ ₂SiC>2/2 units; MT resins having R⁵ ₃Si0_1/2 units and R⁵Si0_3/2 units; MTD resins having R⁵ ₃Si0_1/2 units, R⁵Si0_3/2 units, and R^SiO^ units, and combinations thereof; wherein each R⁵ group is independently a monovalent organic group having from 1 -20 carbon atoms.

[0063] The organosilicon compounds may comprise a linear siloxane polymer comprising combinations of units selected from M, D, R⁶ ₃Si0_1/2 units, and R⁶ ₂SiC>2/2 units. The organosilicon compound may further comprise a branched polymer comprising combinations of units selected from M, D, T, R⁶ ₃Si0_1/2 units, R⁶ ₂SiC>2/2 units, and R⁶Si0_3/2 units. The organosilicon compounds may comprise a siloxane resin selected from MQ resins having R⁶ ₃SiOi_/2 units and Si0_4/2 units; TD resins having R⁶Si0_3/2 units and R⁶ ₂Si0_2/2 units; MT resins having R⁶ ₃SiOi_/2 units and R⁶Si0_3/2 units; MTD resins having R⁶ ₃SiOi_/2 units, R⁶Si0_3/2 units, and R⁶ ₂Si0_2/2 units, and combinations thereof; wherein each R⁶ group is independently a monovalent organic group having from 1-20 carbon atoms and may be a free radical polymerizable group. In some embodiments, the free radical polymerizable group is selected from an acrylate, a methacrylate, a vinyl ether, or an allyl ether group.

[0064] In the preparation of the surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment B, at least one organoborane compound that is capable of generating a free-radical and initiating free-radical addition polymerization and/or crosslinking may be used. The at least one organoborane compound may be a stabilized organoborane compound(s) that renders the organoborane non-pyrophoric at ambient conditions. The at least one organoborane compound may further be a complex formed between an organoborane and a suitable organonitrogen that renders the complex stable at ambient conditions, wherein a free-radical is generated (and polymerization is initialized) upon introduction of an organonitrogen-reactive compound in the presence of oxygen. Examples of suitable organonitrogens for forming the organoborane-organonitrogen complexes of include organopolysiloxanes having least one amine functional group and alkylborane-organonitrogen complexes. The at least one organoborane compound may also be an organoborane compound wherein a free-radical is generated (and polymerization is initiated) upon heating. The at least one organoborane compound may further be a solvent- stabilized organoborane where the solvent is allowed to evaporate to liberate the borane and thereby create a radical. One of skill in the art will understand that any organoborane may be used.

[0065] In some embodiments, the at least one organoborane compound is an organoborane-organonitrogen complex that may be selected from complexes having the formula:

wherein B represents boron and N represents nitrogen; wherein at least one of R6, R7, and R8 contains one or more silicon atoms with the silicon-containing group(s) covalently attached to boron; wherein R6, R7, and R8 are groups that can be independently selected from hydrogen, a cycloalkyl group, a linear or branched alkyl group having 1-12 carbon atoms on the backbone, an alkylaryl group, an organosilane group such as an alkylsilane or an arylsilane group, an organosiloxane group, an alkylene group capable of functioning as a covalent bridge to another boron atom, a divalent organosiloxane group capable of function as a covalent bridge to another boron atom, or halogen substituted homologues thereof; wherein R9, R10, and R1 1 are groups that yield an amine compound or a polyamine compound capable of complexing with boron and are independently selected from hydrogen, an alkyl group containing 1-10 carbon atoms, a halogen substituted alkyl group containing 1- 10 carbon atoms, or an organosilicon functional group; and wherein at least two of the R6, R7, and R8 groups and at least two of the R9, R10, and R1 1 groups can combine to form heterocyclic structures, provided that the sum of the number of atoms from the two combining groups does not exceed 1 1.

[0066] Where an organoborane-organonitrogen complex is used, at least one organonitrogen-reactive compound may also be used. The presence of such an organonitrogen-reactive compound allows for polymerization and/or crosslinking to occur rapidly at temperatures below the dissociation temperature of the organoborane- organonitrogen complexes, including at room temperature and below.

[0067] Nonlimiting examples of suitable organonitrogen-reactive compounds include carboxylic acids such as acetic acid, acrylic acid, methacrylic acid, polyacrylic acid, polymethacrylic acid; anhydride functional compounds; epoxy-functional compounds; and silicon containing compounds that, when exposed to moisture, release an acid that causes the organoborane-organonitrogen complex to disassociate and compounds capable of generating organonitrogen-reactive groups when exposed to ultraviolet radiation. In some embodiments, when an organoborane-organonitrogen complex of the organoborane initiator is used, a separate organonitrogen-reactive compound is not required. Examples of such cases include embodiments where the hydrogel or hydrogel microparticles comprise one or more amine reactive groups, such as those described for Embodiment A. One of skill in the art will recognize that the selection of the organonitrogen-reactive compound will depend upon, among other things, the nature of the organoborane initiator.

[0068] When an organonitrogen-reactive compound is used, free-radical generation requires the presence of oxygen. In some embodiments, merely exposing the organonitrogen- reactive compound or the composition containing the organonitrogen-reactive compound to air is sufficient to induce polymerization. In some embodiments, there is sufficient oxygen dissolved in the reaction mixture to induce polymerization, and it may be advantageous to purge the headspace with an inert gas such as nitrogen. To prevent premature polymerization in the presence of oxygen, the organoborane initiator and the organonitrogen-reactive compound may be physically or chemically isolated until just prior to the desired time to initiate polymerization and/or crosslinking reactions.

[0069] In some embodiments, when an organoborane-organonitrogen complex of the organoborane initiator is used, an organonitrogen-reactive compound is not required. In such cases, free-radical polymerization may be initiated by exposing the organoborane compound to air, by thermal activation, or via radiation.

[0070] One or more active ingredients may be used in the production of the siloxane surface-modified hydrogels and hydrogel microparticles of Alternative Embodiment B. The least one active ingredient may be selected from personal care or healthcare active ingredients or from agricultural active ingredients as detailed below. The active ingredient may be added during the making of the hydrogel or hydrogel microparticle (pre-load method), added after formation of the hydrogel or hydrogel microparticle (post-load method), or added after formation of the surface-modified hydrogel or hydrogel microparticle (post- modification method).

Optional Component D, SiH Functional Orqanopolvsiloxane

[0071] The silicone compositions in their pre-cured state optionally include at least one SiH functional organopolysiloxane (Component D). The SiH functional organopolysiloxane is a multifunctional crosslinker for the addition curable organopolysiloxane. The SiH functional organopolysiloxane is an organosilicon compound having an average of at least two silicon- bonded hydrogen atoms per molecule, alternatively at least three silicon-bonded hydrogen atoms per molecule. In some embodiments, the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule is an organohydrogenpolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule. The organosilicon compound can function as a cross-linker when the composition is cured, for example via hydrosilylation.

[0072] The organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule can be an organohydrogenpolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule. The organosilicon compound can be a homopolymer or a copolymer. The organosilicon compound can have a linear, branched, cyclic, or resinous structure. The silicon-bonded hydrogen atoms in the organosilicon compound can be located at terminal, pendant, or at both terminal and pendant positions. The organosilicon compound can be free of fluorine atoms.

[0073] The organosilicon compound can include siloxane units including, but not limited to, HR⁶2Si0_1/2! R⁶3Si0_1/2! HF^SiO^, R⁶ ₂Si0_2/2, R⁶Si0_3/2, and Si0_4/2 units. In the preceding formulae, each R⁶ is independently selected from monovalent organic groups free of aliphatic unsaturation.

[0074] The organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule can include a compound of the formula

(f) R⁷ ₃SiO(R⁷ ₂SiO)_e(R⁷HSiO)₊SiR⁷3, or

(g) R^HSiOCR^SiO^HSiO^SiR^H, or

(h) a combination thereof.

[0075] In formula (f), ε has an average value of 0 to 2000, and φ has an average value of 2 to 2000. Each R⁷ is independently a monovalent organic group free of aliphatic unsaturation. These monovalent organic groups may have 1 to 20 carbon atoms, alternatively 1 to 10 carbon atoms, and are exemplified by, but not limited to alkyl groups, aromatic groups, cyano-functional groups exemplified by cyanoalkyi groups, halogenated hydrocarbon groups, aminoalkyl groups, hindered aminoalkyl groups, epoxyalkyl groups, ester functional groups, hydroxyl functional groups, isocyanate and masked isocyanate functional groups, aldehyde functional groups, anhydride functional groups, carboxylic acid functional groups, and metal salts of carboxylic acids.

[0076] In formula (g), γ has an average value of 0 to 2000, and η has an average value of 0 to 2000. Each R⁸ is independently a monovalent organic group free of aliphatic unsaturation. Suitable monovalent organic groups free of aliphatic unsaturation include alkyl groups such as methyl, ethyl, propyl, and butyl; halogenated hydrocarbon groups such as 6,6,6,5,5,4,4,3,3-nonafluorohexyl, 4,4,4,3,3-pentafluorobutyl, 5,5,5,4,4,3,3-heptafluoropentyl, 3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl; aromatic groups such as phenyl, tolyl, and xylyl; and cyano-functional groups exemplified by cyanoalkyi groups such as cyanoethyl and cyanopropyl.

[0077] The organosilicon compound can include, for example, a methylhydrogensiloxy- terminated polydimethylsiloxane, dimethylhydrogensiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), dimethylhydrogensiloxy-terminated polymethylhydrogensiloxane, trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), trimethylsiloxy-terminated polymethylhydrogensiloxane, trimethylsiloxy-terminated poly(methylhydrogensiloxane/methyl-3,3,3-trifluoropropylsiloxane), trimethylsiloxy-terminated poly(methylhydrogensiloxane/dimethyl/methyl-3,3,3-trifluoropropylsiloxane), trimethylsiloxy- terminated poly(methylhydrogensiloxane/methyl-6,6,6,5,5,4,4,3,3-nonafluorohexylsiloxane), trimethylsiloxy-terminated poly(methylhydrogensiloxane/dimethyl/methyl-6,6,6,5,5,4,4,3,3- nonafluorohexylsiloxane), and a resin consisting essentially of H(CH₃)₂SiOi/2 units and Si0_4/2 units, and combinations thereof.

[0078] The organosilicon compound can be a combination of two or more organohydrogensilanes or organohydrogenpolysiloxanes that differ in at least one of the following properties: structure, average molecular weight, viscosity, siloxane units, and sequence.

[0079] In some embodiments, the organosilicon compound can be an organohydrogensilane or an organohydrogensiloxane. The organohydrogensilane can be a monosilane, disilane, trisilane, or polysilane. Similarly, the organohydrogensiloxane can be a disiloxane, trisiloxane, or polysiloxane. The structure of the organosilicon compound can be linear, branched, cyclic, or resinous. Cyclosilanes and cyclosiloxanes can have from 3 to 12 silicon atoms, alternatively from 3 to 10 silicon atoms, alternatively from 3 to 4 silicon atoms. In acyclic polysilanes and polysiloxanes, the silicon-bonded hydrogen atoms can be located at terminal, pendant, or at both terminal and pendant positions.

[0080] Examples of organohydrogensiloxanes include, but are not limited to, 1 ,1 ,3,3- tetramethyldisiloxane, 1 ,1 ,3,3-tetraphenyldisiloxane, phenyltris(dimethylsiloxy)silane, 1 ,3,5- trimethylcyclotrisiloxane, a trimethylsiloxy-terminated poly(methylhydrogensiloxane), a trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), a dimethylhydrogensiloxy-terminated poly(methylhydrogensiloxane), and a resin including HMe₂Si0_1/2 units, Me₃Si0_1/2 units, and Si0_4/2 units, wherein Me is methyl. In another example, a suitable organohydrogensiloxane includes a hydridosiloxy functional siloxane resin including (CH₃)₃Si0_1/2 units, (CH₃)₂HSi0_1/2 units and Si0_4/2 units; in some examples this crosslinker has a ratio of (CH₃)₂HSi0_1/2 units to Si0_4/2 units of approximately 1.82; in some examples, the organohydrogensiloxane includes about 1 wt% H in the form of SiH; in some examples, the organohydrogensiloxane has an average viscosity of about 0.02 Pa-s at 25°C. In another example, a suitable organohydrogensiloxane includes a trifluoropropyl- silsesquioxane; in some examples, the organohydrogensiloxane has an average viscosity of about 0.005 Pa-s at 25°C; in some examples, the organohydrogensiloxane includes about 0.55 wt% H in the form of SiH. In another example, a suitable organohydrogensiloxane includes a polydimethylsiloxane-polyhydridomethylsiloxane copolymer; in some examples, the organohydrogensiloxane has an average viscosity of about 0.005 Pa-s at 25°C; in some examples, the organohydrogensiloxane includes about 0.75 wt% H in the form of SiH.

[0081] According to one embodiment, the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule is at least one organohydrogenpoly- siloxane having the average unit formula (i)

(R¹ ₂R³Si0_1/2)_m(R¹R³Si0_2/2)_n(R¹Si0_3/2)_p(Si0_4/2)_q wherein each R¹ is independently C-i to C₁₀ hydrocarbyl or C-i to C₁₀ halogen-substituted hydrocarbyl, both free of aliphatic unsaturation, each R³ is independently R¹ or -H, m is from 0.001 to 0.3, n is from 0.5 to 0.999, p is from 0 to 0.5, q is from 0 to 0.5, and m+n+p+q is approximately equal to 1 , provided the organohydrogenpolysiloxane has an average of at least two silicon-bonded hydrogen atoms per molecule. The hydrocarbyl and halogen- substituted hydrocarbyl groups represented by R¹ are as described and exemplified above.

[0082] The organohydrogenpolysiloxane having the average unit formula (i) has a linear or branched structure. The organohydrogenpolysiloxane can be a homopolymer containing identical repeat units or a copolymer containing two or more different repeat units. In a copolymer, the units can be in any order. For example, the organohydrogenpolysiloxane can be a random, alternating, or block copolymer.

[0083] In the average unit formula (i) of the organohydrogenpolysiloxane, the subscripts m, n, and p are mole fractions. The subscript m typically has a value of from 0.001 to 0.3, alternatively from 0.02 to 0.15, alternatively from 0.02 to 0.05; the subscript n typically has a value of from 0.5 to 0.999, alternatively from 0.6 to 0.9, alternatively from 0.7 to 0.9; the subscript p typically has a value of from 0 to 0.5, alternatively from 0 to 0.3, alternatively from 0 to 0.15; and the subscript q typically has a value of from 0 to 0.5, alternatively from 0 to 0.3, alternatively from 0 to 0.15.

[0084] In some examples, at least 50 mol%, alternatively at least 65 mol%, alternatively at least 80 mol% of the groups R³ in the organohydrogenpolysiloxane are hydrogen. The term "mol% of the groups R³ in the organohydrogenpolysiloxane are hydrogen" is defined as the ratio of the number of moles of silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane to the total number of moles of the groups R³ in the organohydrogenpolysiloxane, multiplied by 100.

[0085] In some examples, the organohydrogenpolysiloxane typically has a number-average molecular weight (M_n) of from 500 to 50,000, alternatively from 1000 to 20,000, alternatively 2,000 to 10,000, where the molecular weight is determined by gel permeation chromatography employing a refractive index detector and polydimethylsiloxane standards.

[0086] In some examples, the organohydrogenpolysiloxane typically has a viscosity of from 0.001 to 100,000 Pa-s, alternatively from 0.1 to 10,000 Pa-s, alternatively from 0.2 to 20 Pa-s, at 25°C.

[0087] Examples of organohydrogenpolysiloxanes having the average unit formula (i) include, but are not limited to, polysiloxanes having the following formulae: Me₃SiO(MeHSi02/2)bSiMe₃, Me₃SiO(MeHSi02/2)b(Me2Si02/2)cSiMe₃, [Me₃SiO(MeHSi0_2/2)b]3(MeSi0_3/2), HMe₂SiO(MeHSi0_2/2)a(Me₂Si0_2/2)_bSiMe₂H, HMe₂SiO(MeHSi0_2/2)a(PhMeSi0_2/2)_bSiMe₂H, and HMe2SiO(MeHSi02/2)a( hMeSi02/2)b(MeSi0₃/2)cSiMe2H, where Me is methyl, and the subscripts b and c, which denote the average numbers of the enclosed units, have values such that the organohydrogenpolysiloxane has a number-average molecular weight of from 500 to 50,000.

[0088] An example of a suitable organohydrogenpolysiloxane of average unit formula (i) includes a trimethylsiloxy-terminated poly(methylhydrogensiloxane/methyl-6,6,6,5,5,4,4,3,3- nonafluorohexylsiloxane); in some examples this crosslinker has an average of 28 methylhydrogensiloxane units and 12 methyl-6,6,6,5,5,4,4,3,3-nonafluorohexyl siloxane units per molecule. Another example of a suitable organohydrogenpolysiloxane of average unit formula (II) includes a polydimethylsiloxane-polyhydridomethylsiloxane copolymer; in some examples this crosslinker has an average viscosity of 0.03 Pa-s at 25°C and includes 1 wt% H in the form of SiH.

[0089] The organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule can be a single organosilicon compound or a mixture including two or more different organosilicon compounds, each as described above. For example, the organosilicon compound can be a single organohydrogensilane, a mixture of two different organohydrogensilanes, a single organohydrogensiloxane, a mixture of two different organohydrogensiloxanes, or a mixture of an organohydrogensilane and an organohydrogensiloxane.

[0090] The molar ratio of silicon-bonded hydrogen atoms in the organosilicon compound having an average of at least two silicon-bonded hydrogen atoms per molecule to aliphatically unsaturated groups in the organopolysiloxane having an average of at least two silicon-bonded alkenyl groups per molecule (SiHA i) is not critical. However, the components in the composition may be selected such that the molar ratio of the total number of silicon-bonded hydrogen atoms to aliphatically unsaturated groups in the composition (SiHtot Vitot) is greater than 0.5 and, alternatively, at least 0.9. SiH_totA itot may be up to 10.0 and, alternatively, up to 5.0. Without wishing to be bound by theory, it is thought that if SiHtotA itot is too low, then the composition may not cure or may not adhere to some substrates. Without wishing to be bound by theory, it is thought that if SiH_totA it₀t is too high, surface properties such as adhesion may be hindered and there may be an increase in bleed from within the formulation to other surfaces.

[0091 ] Methods of preparing organosilicon compounds containing silicon-bonded hydrogen atoms are well known in the art. For example, organohydrogensilanes can be prepared by reaction of Grignard reagents with alkyl or aryl halides.

[0092] Methods of preparing organohydrogensiloxanes and linear, branched, and cyclic organohydrogenpolysiloxanes suitable for use as the organosilicon compound, such as hydrolysis and condensation of organohalosilanes, are well known in the art. Methods of preparing organohydrogenpolysiloxane resins suitable for use as the organosilicon compound are also well known in the art.

[0093] The amount of Component D present in the silicone compositions may vary, but in some embodiments ranges from about 0.25% to about 17% (by weight), alternatively from about 0.1 % to about 26% (by weight), alternatively from about 0.05% to about 38% (by weight), based on the amount by total weight of components in the composition.

Optional Component E, Active Ingredient

[0094] The silicone compositions in their pre-cured state optionally include at least one active ingredient (Component E). Generally, optional Component E comprises at least one active ingredient selected from personal care or healthcare active ingredients or from agricultural active ingredients. The active ingredient that is selected may based on a desired solubility of the active ingredient in water. For example, in some embodiments, the desired solubility of the active ingredient in water is at least about 1.0 mg/L.

[0095] As used herein, a "personal care or healthcare active ingredient" means any compound or mixtures of compounds that may be used as additives in personal care formulations that are typically added for the purpose of providing a cosmetic and/or aesthetic benefit, a pharmaceutical or medical benefit, a pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body of a human or other animals. Thus, "personal care and healthcare active ingredient" includes, but is not limited to, an active ingredient or active drug ingredient as generally used and defined by the United States Department of Health & Human Services Food and Drug Administration, contained in Title 21 , Chapter I, of the Code of Federal Regulations, Parts 200-299 and Parts 300-499.

[0096] The active ingredient can be present in different forms, depending on which form yields optimum desired delivery characteristics such as the desired release rate and the desired total amount released. For example, in the case of drugs, the drug can be present in its free base or acid form or in the form of salts, esters or any other pharmacologically acceptable derivative(s) or as component(s) of molecular complexes.

[0097] The amount of the active ingredient incorporated into the system varies depending on many factors including, but not limited to, the particular active ingredient, the desired therapeutic effect, and the time span for which the system is to provide therapy. The amount of optional Component E present in the silicone compositions may vary, but in some embodiments ranges from about 0% to about 90% (by weight), alternatively from about 0.01 % to about 25% (by weight), alternatively from about 0.5% to about 10% (by weight), based on the amount by total weight of components in the composition. The weight of the system is, at a minimum, the combined weight of the active ingredient, the silicone-hydrogel and the silicone elastomer matrix.

[0098] It is contemplated that the active ingredient should be suitable for transdermal or localized topical delivery to a substrate. Often, the passage of the active ingredient through the skin is the rate-limiting step in transdermal delivery. The minimum amount of active ingredient in the system is selected based on the amount of active ingredient which passes through the skin, or other substrate, in the time span for which the system is to provide therapy.

[0099] In some embodiments, active ingredients suitable for Component E include both fat or oil-soluble vitamins, as well as water-soluble vitamins. Oil-soluble vitamins include, but are not limited to, Vitamin A1 , RETINOL, C2-C18 esters of RETINOL, Vitamin E, TOCOPHEROL, esters of Vitamin E, and mixtures thereof. RETINOL includes trans- RETINOL, 1 , 3-cis-RETINOL, 1 1-cis-RETINOL, 9-cis-RETINOL, and 3,4-didehydro- RETINOL. It should be noted that RETINOL is an International Nomenclature Cosmetic Ingredient Name (I NCI) designated by The Cosmetic, Toiletry, and Fragrance Association (CTFA), Washington DC, for Vitamin A. Water-soluble vitamins include, but are not limited to, Vitamin C, Vitamin B1 , Vitamin B2, Vitamin B6, Vitamin B12, niacin, folic acid, biotin, and pantothenic acid.

[00100] In some embodiments, the personal care or healthcare active ingredient used as Component E can be a water-soluble or an oil-soluble active drug ingredient. Representative nonlimiting examples of some suitable water-soluble active drug ingredients which can be used are hydrocortisone, ketoprofen, niacinamide, salicylic acid, and ketoconazole. Representative nonlimiting examples of some suitable oil-soluble active drug ingredients are clonidine, scopolamine, atropine, haloperidol, isosorbide, nitroglycerin, ibuprofen, naproxen, and steroids.

[00101] Considered to be included herein as active drug ingredients for purposes of the present invention are anti-acne agents such as benzoyl peroxide and tretinoin; antibacterial agents such as chlorohexadiene gluconate; antifungal agents such as miconazole nitrate; anti-inflammatory agents; corticosteroidal drugs; non-steroidal anti-inflammatory agents such as diclofenac; antipsoriasis agents such as clobetasol propionate; anaesthetic agents such as lidocaine; antipruritic agents; and antidermatitis agents.

[00102] In some embodiments, Component E can also be a protein, such as an enzyme. Enzymes include, but are not limited to, commercially available types, improved types, recombinant types, wild types, variants not found in nature, and mixtures thereof. For example, suitable nonlimiting enzymes include hydrolases, cutinases, oxidases, transferases, reductases, hemicellulases, esterases, isomerases, pectinases, lactases, peroxidases, laccases, catalases, and mixtures thereof.

[00103] In some embodiments, Component E may be a sunscreen agent. The sunscreen agent can be selected from any sunscreen agent known to protect skin from the harmful effects of exposure to sunlight. The sunscreen can be an organic compound, an inorganic compound, or mixtures thereof. Thus, representative nonlimiting examples that can be used as the sunscreen agent include Diethanolamine Methoxycinnamate, Dioxybenzone, Octocrylene, Red Petrolatum, Sulisobenzone, Titanium Dioxide, and Trolamine Salicylate. Where the sunscreen is an organic compound, the organic sunscreen compound is typically chosen from an organic compound that absorbs ultraviolet (UV) light. Alternatively, the sunscreen agent may be a cinnamate based organic compound, or alternatively, the sunscreen agent may be octyl methoxycinnamate, such as UVINUL® MC 80 an ester of para-methoxycinnamic acid and 2-ethylhexanol available from BASF Corporation, Mount Olive, New Jersey.

[00104] In some embodiments, Component E may be any perfume or fragrance active ingredient. These compositions typically belong to a variety of chemical classes, as varied as alcohols, aldehydes, ketones, esters, ethers, acetates, nitrites, terpenic hydrocarbons, heterocyclic nitrogen or sulphur containing compounds, as well as essential oils of natural or synthetic origin. Fragrance active ingredients may be exemplified by, but not limited to, perfume ketones and perfume aldehydes. Perfume ketones and aldehydes may be, but are not required to be, selected for odor character. In the above list of perfume active ingredients, some are commercial names conventionally known to one skilled in the art, and also includes isomers.

[00105] In some embodiments, Component E may be one or more plant extracts. Nonlimiting examples of these components include Ashitaba extract, avocado extract, Althea extract, Arnica extract, aloe extract, apricot extract, apricot kernel extract, Ginkgo biloba extract, fennel extract, oolong tea extract, rose fruit extract, Echinacea extract, honey, Roman Chamomile extract, and royal jelly extract.

[00106] In some embodiments, Component E comprises at least one agricultural active ingredient. As used herein, an "agricultural active ingredient" means any compound or mixtures of compounds that may be additives in formulations that are typically added for the purpose of treating plants. The agricultural active ingredient(s) selected will typically need to comport with a specific application need. Accordingly, the agricultural active ingredient(s) selected may be present in varying amounts, as well as in varying physical forms, such as solid particles, liquid, or semiliquid form. In some embodiments, the agricultural active ingredient(s) selected may be between about 0 and about 50% (by weight), based on the amount by total weight of components in the composition. Optional Component F, Surfactant

[00107] According to some embodiments, at least one surfactant can optionally be added during treatment of the hydrogels and the hydrogel microparticles according to the methods described herein. Generally, the surfactant can be any known surfactant and can be cationic, anionic, nonionic and/or amphoteric. Furthermore, the surfactant can be aqueous, non-aqueous, and/or in diluted or undiluted form.

[00108] Nonlimiting examples of suitable cationic surfactants include, but are not limited to, quaternary ammonium hydroxides as well as corresponding salts of these materials, fatty amines and fatty acid amides and their derivatives, basic pyridinium compounds, and quaternary ammonium bases of benzimidazolines and poly(ethoxylated/propoxylated) amines.

[00109] Nonlimiting examples of anionic surfactants include, but are not limited to, alkyl sulfates such as lauryl sulfate, polymers such as acrylates/Cio-30 alkyl acrylate crosspolymer alkylbenzenesulfonic acids and salts, the sulfate esters of monoalkyl polyoxyethylene ethers, alkylnapthylsulfonic acid, alkali metal sulfoccinates, sulfonated glyceryl esters of fatty acids, salts of sulfonated monovalent alcohol esters, amides of amino sulfonic acids, sulfonated products of fatty acid nitriles, sulfonated aromatic hydrocarbons, condensation products of naphthalene sulfonic acids with formaldehyde, sodium octahydroanthracene sulfonate, alkali metal alkyl sulfates, ester sulfates, and alkarylsulfonates. Anionic surfactants include alkali metal soaps of higher fatty acids, alkylaryl sulfonates, long chain fatty alcohol sulfates, olefin sulfates and olefin sulfonates, sulfated monoglycerides, sulfated esters, sulfonated ethoxylated alcohols, sulfosuccinates, alkane sulfonates, phosphate esters, alkyl isethionates, alkyl taurates, and alkyl sarcosinates.

[00110] Nonlimiting examples of suitable non-ionic surfactants include, but are not limited to, condensates of ethylene oxide with long chain fatty alcohols or fatty acids, condensates of ethylene oxide with an amine or an amide, condensation products of ethylene and propylene oxide, esters of glycerol, sucrose, sorbitol, fatty acid alkylol amides, sucrose esters, fluoro- surfactants, fatty amine oxides, polyoxyalkylene alkyl ethers, polyoxyalkylene sorbitan ethers, polyoxyalkylene alkoxylate esters, polyoxyalkylene alkylphenol ethers, ethylene glycol propylene glycol copolymers and alkylpolysaccharides, and polymeric surfactants. In certain embodiments, the surfactant is a polyoxyethylene fatty alcohol or mixture of polyoxyethylene fatty alcohols. In other embodiments, the surfactant is an aqueous dispersion of a polyoxyethylene fatty alcohol or mixture of polyoxyethylene fatty alcohols.

[00111] Nonlimiting examples of amphoteric surfactants include cocamidopropyl betaine, cocamidopropyl hydroxysulfate, cocobetaine, sodium cocoamidoacetate, cocodimethyl betaine, N-coco-3-aminobutyric acid and imidazolinium carboxyl compounds. [00112] In some embodiments, the surfactant may be selected from TERGITOL® 15-S-3 or 15-S-40 available from The Dow Chemical Company, Midland, Michigan, sorbitan monooleate, polylycol-modified trimethsilylated silicate, polyglycol-modified siloxanes, polyglycol-modified silicas, ethoxylated quaternary ammonium salt solutions, and cetyltrimethylammonium chloride solutions.

[00113] The amount of optional surfactant present in the silicone compositions may vary, but in some embodiments ranges from about 0.05% to about 10% (by weight), alternatively from about 0.025% to about 20% (by weight), alternatively from about 0.01 % to about 50% (by weight), based on the amount by total weight of components in the composition.

Additional Optional Components

[00114] The silicone compositions may optionally include additional components. Without limitation, examples of such optional additional components include cure modifiers or inhibitors; emulsifiers; dispersants; rheology modifiers such as thickeners or thickening agents; pharmaceutical agents; cosmetic agents; resins such as non-functional silicone resins; density modifiers; anti-void additives; low temperature cure inhibitors; additives for improving adhesion; aziridine stabilizers; polymers and copolymers; diluents; acid acceptors; antioxidants; heat stabilizers; flame retardants; scavenging agents; silylating agents; foam stabilizers; solvents; diluents; plasticizers; fillers and inorganic particles, pigments, dyes and dessicants; solvents; powders; coloring agents; waxes or wax-like materials; stabilizing agents; pH regulators; silicones; and fluids or other materials conventionally used in silicone elastomers.

[00115] Cure inhibitors may optionally be added to the silicone compositions. Any suitable platinum group type inhibitor may be used. Nonlimiting suitable platinum catalyst inhibitors include acetylenic inhibitors, olefinic siloxanes and polymethylvinylcyclosiloxanes having three to six methylvinylsiloxane units per molecule. A preferred class of acetylenic inhibitors is the acetylenic alcohols, especially 2-methyl-3-butyn-2-ol and/or 1-ethynyl-2-cyclohexanol which suppress the activity of a platinum-based catalyst at 25° C.

[00116] Compositions containing these cure inhibitors typically require heating at temperatures of 70°C or above to cure at a practical rate. Room temperature cure is typically accomplished with such systems by use of a two-part system in which the cross- linker and inhibitor are in one of the two parts and the platinum is in the other part. The amount of platinum is increased to allow for curing at room temperature. The optimum concentration of platinum catalyst inhibitor is that which will provide the desired storage stability or pot life at ambient temperature without excessively prolonging the time interval required to cure the present compositions at elevated temperatures. This amount will vary widely and will depend upon the particular inhibitor that is used, the nature and concentration of the platinum-containing catalyst, and the nature of the cross-linker. The amount of inhibitor present in the silicone compositions contemplated herein may vary but in some embodiments ranges from about 0 to about 0.1 % (by weight) and in other embodiments ranges up to about 0.5% (by weight) based on the amount by total weight of components in the composition. The optimum concentration for a particular inhibitor in a given composition can be determined by routine experimentation.

[00117] Thickening agents may optionally be added to the aqueous phase of the silicone compositions to provide a convenient viscosity. For example, viscosities within the range of about 500 to about 25,000 mm²/s at about 25°C or more, alternatively in the range of about 3,000 to about 7,000 mm²/s at about 25°C, are usually suitable. Suitable thickening agents are exemplified by sodium alginate; gum arabic; polyoxyethylene; guar gum; hydroxypropyl guar gum; ethoxylated alcohols; cellulose derivatives; starch and starch derivatives; locust bean gum; electrolytes; saccharides; and derivatives of saccharides; or mixtures of two or more of these. Alternatively the thickening agent is selected from cellulose derivatives, saccharide derivatives, and electrolytes, or from a combination of two or more of the above thickening agents exemplified by a combination of a cellulose derivative and any electrolyte, and a starch derivative and any electrolyte. The thickening agent may be present in an amount from about 0.05 to about 10 wt%; alternatively from about 0.05 to about 5 wt%, based on the total weight of the composition. Thickeners based on acrylate derivatives may also be added.

[00118] Stabilizing agents may optionally be used in the water phase of the provided compositions. Suitable water phase stabilizing agents can include alone or in combination one or more electrolytes, polyols, alcohols such as ethyl alcohol, and hydrocolloids. Typical electrolytes are alkali metal salts and alkaline earth salts, especially the chloride, borate, citrate, and sulfate salts of sodium, potassium, calcium and magnesium, as well as aluminum chlorohydrate, and polyelectrolytes, especially hyaluronic acid and sodium hyaluronate. When the stabilizing agent is, or includes, an electrolyte, it amounts to about 0.1 to about 5 wt% and more alternatively about 0.5 to about 3 wt% of the total composition. The hydrocolloids include gums, such as Xantham gum or Veegum and thickening agents, such as carboxymethyl cellulose. Polyols, such as glycerine, glycols, and sorbitols can also be used. Alternative polyols are glycerine, propylene glycol, sorbitol and butylene glycol. If a large amount of a polyol is used, one need not add the electrolyte. However, it is typical to use a combination of an electrolyte, a polyol and a hydrocolloid to stabilize the water phase, e.g. magnesium sulfate, butylene glycol and Xantham gum.

[00119] Other optional components can include powders and pigments. A powder composition can be generally defined as dry, particulate matter having a particle size of 0.02-50 microns. The particulate matter may be colored or non-colored (for example white). Suitable powders include, but are not limited to, fumed silica, spherical silica beads, aluminum silicate, magnesium aluminum silicate, silica, and titanium dioxide. The above- mentioned powders may be surface treated to render the particles hydrophobic in nature. The powder component also comprises various organic and inorganic pigments.

[00120] Pulverulent inorganic or organic fillers can also be added, generally in an amount by weight from 0 to 40% with respect to the weight of the final composition. These pulverulent fillers can be chosen from talc, micas, kaolin, zinc or titanium oxides, calcium or magnesium carbonates, silica, spherical titanium dioxide, glass or ceramic beads, metal soaps derived from carboxylic acids having 8-22 carbon atoms, non-expanded synthetic polymer powders, expanded powders and powders from natural organic compounds, copolymer microspheres such as EXPANCEL® available from AkzoNobel, The Netherlands, polytrap and silicone resin microbeads such as TOSPEARL® available from GE Silicone Toshiba, Tokyo.

[00121] Waxes or wax-like materials may be optional components of the provided silicone compositions, wherein such components generally have a melting point range of about 35°C to about 120°C at atmospheric pressure. , Mention may be made, among the waxes capable of being used as non-silicone fatty substances, of animal waxes, such as beeswax; vegetable waxes, such as carnauba, candelilla wax; mineral waxes, such as ceresin, paraffin, lignite wax, microcrystalline waxes or ozokerites; synthetic waxes, including polyethylene waxes, and waxes obtained by the Fischer-Tropsch synthesis. Mention may be made, among the silicone waxes, of polymethylsiloxane alkyls, alkoxys and/or esters.

[00122] Water soluble or water dispersible silicone polyether compositions may also be optional components. These are also known as polyalkylene oxide silicone copolymers, silicone poly(oxyalkylene) copolymers, silicone glycol copolymers, or silicone surfactants. These can be linear rake or graft type materials, ABA or ABn type where the B is the siloxane polymer block, and the A is the poly(oxyalkylene) group. The poly(oxyalkylene) group can consist of polyethylene oxide, polypropylene oxide, or mixed polyethylene oxide/polypropylene oxide groups. Other oxides, such as butylene oxide or phenylene oxide are also possible.

[00123] The inventive silicone compositions can be used in o/w, s/w, w/o, w/s, and nonaqueous o/o, o/s, and s/o emulsions or multiple phase emulsions using silicone emulsifiers. Typically the water-in-silicone emulsifier in such formulation is non-ionic and is selected from polyoxyalkylene-substituted silicones (rake or ABn type), silicone alkanolamides, silicone esters and silicone glycosides.

[00124] Water-soluble solvents may also be optional components in the silicone compositions. Examples include acetonitrile, tetrahydrofuran, acetone, 1 ,4-dioxane, dimethylsulfoxide.

[00125] When a provided composition is an oil-in-water emulsion, it will include common ingredients generally used for preparing emulsions such as but not limited to nonionic surfactants well known in the art to prepare o/w emulsions. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene lauryl ethers, polyoxyethylene sorbitan monoleates, polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, polyethylene glycol, polypropylene glycol, diethylene glycol, ethoxylated trimethylnonanols, and polyoxyalkylene glycol modified polysiloxane surfactants.

[00126] The inventive silicone compositions can also be in the form of aerosols in combination with propellant gases, such as carbon dioxide, nitrogen, nitrous oxide, volatile hydrocarbons such as butane, isobutane, or propane and chlorinated or fluorinated hydrocarbons such as dichlorodifluoromethane and dichlorotetrafluoroethane or dimethylether.

Curing of the Silicone Compositions Comprising the Siloxane-Modified Hydroqels

[00127] The various ingredients, namely, (a) the addition curable organopolysiloxane (b) the cure catalyst or initiator, (c) the hydrogel or hydrogel microparticle with at least one siloxane- coated surface and optionally (d) the multifunctional crosslinker, (e) the water-soluble active ingredient and (f) the surfactant may be reacted to form silicone compositions comprising siloxane-modified hydrogels. The various ingredients can be reacted; reacting means stirring, mixing or otherwise combining to form a homogenous blend. The resulting silicone compositions can be heated at temperatures ranging from about 15°C to about 225°C to effect curing.

[00128] The resulting silicone compositions may be of any physical form and more, particularly of silicone tacky gel, pressure sensitive adhesive, liquid silicone rubber, high consistency silicone elastomer, silicone adhesive, silicone sealant, or silicone encapsulant are envisioned.

[00129] Where the silicone compositions are in the form of a silicone tacky gel, the silicone tacky gel may be a silicone resin reinforced skin sensitive adhesive. In some embodiments, the silicone gels or skin sensitive adhesives are obtained by reacting an alkenyl-substituted polydiorganosiloxane, particularly a polydimethylsiloxane having silicon-bonded unsaturated alkenyl groups like vinyl, allyl or hexenyl groups, an organosiloxane containing silicon- bonded hydrogen atoms and a catalyst for the reaction of SiH groups with the Si-alkenyl groups, such as a platinum metal or compounds or complexes thereof or other catalysts capable to catalyze silicone-bonded hydrogen to silicon-bonded alkenyl. In other embodiments, silicone resins comprising unsaturated alkenyl groups or silicon hydride functional groups, particularly vinyl-functional MQ resins, may be combined with linear polydiorganosiloxanes to impart useful properties. Such compositions cure at normal ambient temperatures, but curing can be expedited by exposure to elevated temperatures, e.g., from about 40°C to about 225°C. Desired Si-H and Si-alkenyl siloxanes to be used in the above reaction have viscosities in the range of about 5 to about 60,000 mPa/s. The desired ratio of (H as SiH)(Alkenyl as Si-Alkenyl) is generally in the range of about 0.1 :1 to about 10:1 .

[00130] Where the silicone compositions described herein are in the form of a liquid silicone rubber or a high consistency elastomer, the liquid silicone rubber or high consistency elastomer, respectively, are composed minimally of polydimethylsiloxanes having vinyl and silicon hydride groups although other substituents are conceivable. The viscosities typically range from about 0.65 to about 10,000,000 mPa/s. In order to achieve final properties, fillers and additives are generally added to the liquid silicone rubber or a high consistency elastomer.

Uses of the Silicone Compositions Comprising the Siloxane-Modified Hydroqels

[00131] The silicone compositions described herein may be used in a variety of applications, including, life science or healthcare applications such as medical devices, wound dressings, wound care materials such as adhesives, transdermal patches, cosmetics, multi-layered contact lens materials, tissue scaffolds; moisture-curable construction sealants; agricultural applications such as water conservation for agrarian and civilian distribution systems; delivery and moisture management for personal care applications; silicone-hydrogel hybrid wound care materials, water-swellable materials for water sealing solutions; and other applications where silicone-water interfaces are involved. The silicone compositions described herein are particularly useful in applications in which water or water-soluble actives are sought to be carried in a crosslinkable silicone matrix.

[00132] One important application for the silicone compositions of the present invention is in drug delivery systems. This can take many forms including, but not limited to, transdermal patches, films, wound dressings, multi-layer dressings, reservoir systems, drug eluting or delivering medical devices and combinations thereof. Nonlimiting examples of drug eluting or drug delivering medical devices include stents, shunts, catheters, drains, bulbs, inserts, and implants. The active agent is in the system for controlled delivery of the active, for example, to a substrate. One desired application of the transdermal drug delivery system of the present invention is to treat a user, or patient, with the active agent. As a result, the substrate is typically the skin of the user and the user applies and wears the system on their skin for controlled delivery of the active to the skin. In this application, it is possible, but not required, for the system to include a backing layer for supporting the composition, and/or a release liner for protecting the composition and/or the active agent prior to the controlled transdermal delivery of the active agent to the substrate. Another desired application of the drug delivery system of the present invention is to incorporate the silicone compositions into a drug eluting or drug delivering medical device. As a result, the drug delivery system may be placed inside or implanted in the body of the user for controlled delivery of the active. EXAMPLES

[00133] The present invention will be better understood by reference to the following examples which are offered by way of illustration and which one of skill in the art will recognize are not meant to be limiting.

Example 1 : Encapsulated Active in Silicone Surface-Modified Partially Swollen Hydrogel Particles

[00134] Hydrogel particles with a silicone surface were prepared at ambient lab conditions by the following method:

1. 6.5 parts of a microparticulate crosslinked polyacrylic acid copolymer (DPAA-cp) [CARBOPOL® Ultrez 20 (Acrylates / C10-30 Alkyl Acrylate Cross-Polymer particles obtained from The Lubrizol Corporation, Wickliffe, Ohio)], 12.7 parts MA- PDMS (epoxy amine terminated polydimethylsiloxane), and 3.1 part sorbitan monooleate to 70.0 parts hexamethyldisiloxane were combined into an 8 oz. straight sided jar and continually mixed using a magnetic stir plate.

2. 6.6 parts of a mixture consisting of 18 parts lidocaine in 82 parts 3.7% hydrochloric acid in water were added drop wise while mixing.

3. 1.1 parts TNBB-MOPA (an initiator complex) were added to the mixture and allowed to mix for a minimum of 2 additional minutes.

4. The resulting material was vacuum filtered through a 0.8 micron nylon filter and rinsed with hexamethyldisiloxane and n-heptane.

5. The resulting material was dried for 2 hrs at 40°C under full vacuum (< 5 mm Hg).

[00135] Under observation with FE-SEM, it appeared that the encapsulated DPAA-cp particles were more bulbous than the neat unmodified DPAA-cp hydrogel microparticles. Further, it was shown that the lidocaine was able to be extracted in significant concentrations (5-12 wt%) from the dried silicone surface-modified CARBOPOL particles as shown by analysis using a variety of ultra performance liquid chromatography (UPLC) methods, such as that outlined below:

1. 0.26 g of the dried resulting material from step 5 was extracted in 15 mL of 1 N HCI by shaking for 1 hour on a wrist action shaker.

2. The solution was centrifuged for 10 minutes at 1500 rpm. 3. 1 mL of the supernatant was diluted to 10 mL in HPLC grade methanol and the sample filtered (0.45 micron syringe filter) and analyzed via a Waters Acquity UPLC (2.1 x 100 mm BEH C18 1.7 μηι column with 30:70 Acetonitrile: 5% HOAc pH 3.4 (adjusted with 1 N NaOH) mobile phase operating at a column temperature of 30°C with a flow rate of 0.4 mL/min (Detection: PDA 254 nm).

[00136] All samples were prepared as an exact 1 :1 weight by weight ratio of A and B parts of S50 LIQUID SILICONE RUBBER, a platinum catalyzed hydrosilylation cured silicone elastomer obtained from Dow Corning Corporation (Midland, Ml). To five of the six samples, silicone-hydrogel material was added to achieve specified weight-by-weight concentration of silicone-hydrogel (i.e., 2.5, 5, 10 and 15% w/w silicone hydrogel). The resultant mixtures were mixed thoroughly and press cured at 150°C to create a slab with nominal thickness of 0.075 inches (1.9 mm). Discs were cut from these slabs, weighed and put over the openings of Payne cups with a known amount (mass) of water. The Payne cups were placed in an oven at 32°C and 50% Relative humidity for 24 hrs. Upon removal from the ovens, the discs were re-weighed and the percentage increase calculated as the absorbency of each material. As shown in Table 1 , the actual numbers were made relative to the initial (control) value.

Table 1

These results illustrate the ability to increase absorbency by more than six fold from the control by using this technique.

Example 2: Encapsulated Lidocaine Active in Silicone Surface-Modified Hydrogel Particles

[00137] Many active agents, including sunscreen agents, pharmaceutical actives, cosmetic, cosmeceutical agents, nutritional and nutriceutical agents have a deleterious effect on the cure rate and the properties of a hydrosilylation cured silicone elastomer. In many cases, the active agent can prevent a complete cure of the elastomer. Ex. 2 illustrates an improvement to the current state of the art by demonstrating a reduction in the deleterious effects of an active pharmaceutical ingredient, lidocaine, when the active is encapsulated in the silicone-hydrogel particle.

[00138] Lidocaine-loaded silicone hydrogel particles were analyzed and found to contain 5% w/w lidocaine. These particles were added to an exact 1 :1 weight by weight ratio of A and B parts of S50 LIQUID SILICONE RUBBER to achieve a final concentration of 0.75% lidocaine (Sample 7).

[00139] Lidocaine was added to an exact 1 :1 weight by weight ratio of A and B parts of S50 LIQUID SILICONE RUBBER to achieve a final concentration of 0.75% lidocaine (Sample 8). Both samples were mixed identically and the cure profile (time to reach cure) and maximum torque achieved during cure was measured on 5 g aliquots of each mixture using an appropriate rheometer. Rheometer settings included 1 15°C set temperature, 50 in-lb torque range, 1 degree arc eccentricity and an 8 minute test time. The actual numbers were made relative to a sample that did not contain any lidocaine.

[00140] Table 2 shows the relative change in properties of liquid silicone rubber and lidocaine preparations with and without silicone hydrogel. As shown in Table 2, both additions had an impact on both the maximum torque and the cure time. However, the changes caused by the addition of lidocaine in silicone hydrogel were substantially less than those caused by a similar loading of lidocaine directly to the liquid silicone rubber.

Table 2

[00141] The maximum torque of the liquid silicone rubber is a measurement of firmness of the material. Sample 2 shows more than a 30% decrease in firmness as a result of the minor addition of 0.75% lidocaine while the lidocaine in the silicone surface-modified hydrogel particle retained 90% of the firmness of a sample without lidocaine.

[00142] Cure time was measured as the time to reach 90% of maximum torque (firmness) of each sample. The sample with only lidocaine required 260% more time than the neat liquid silicone rubber sample and twice as much time as the elastomer with lidocaine in silicone- hydrogel to reach 90% of maximum torque. These results illustrate a substantial increase of the silicone elastomer cure rate and a substantial decrease in overall firmness when loading active substances directly into a silicone rubber. When that same active substance (e.g. lidocaine) is encapsulated in a silicone surface-modified hydrogel, the cure rate and firmness are much less affected. [00143] The present invention should not be considered limited to the specific examples described herein, but rather should be understood to cover all embodiments of the invention. Various modifications and equivalent processes, as well as numerous structures and devices, to which the present invention may be applicable will be readily apparent to those of skill in the art. Those skilled in the art will understand that various changes may be made without departing from the scope of the invention, which is not to be considered limited to what is described in the specification.

Claims

Claims:

1. A method for preparing a siloxane composition comprising reacting:

a. an unsaturated organopolysiloxane;

b. a hydrosilylation catalyst;

c. a hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through an amine-capping reaction to form at least one siloxane-coated surface on the hydrogel or the hydrogel microparticle;

d. optionally a SiH functional organopolysiloxane;

e. optionally a water-soluble active ingredient; and

f. optionally a surfactant.

2. The method of Claim 1 , wherein the hydrogel or hydrogel microparticle is selected from polyacrylic acid, polymethacrylic acid, salts of polyacrylic acid, salts of polymethacrylic acid, poly(2-hydroxyethyl methacrylate), polylactic acid, polyglycolic acid, polyanhydrides such as poly(methacrylic) anhydride, poly(acrylic) anhydride, polysebacic anhydride, hyaluronic acid-containing polymers such as poly(hyaluronic acid), hyaluronic acid containing polymers, or combinations thereof.

3. The method of Claim 1 or Claim 2, wherein the hydrogel or hydrogel microparticle comprise at least one organic polymer comprising amine-reactive groups selected from carboxy-functional groups, sulfonic acid-functional groups, epoxy groups, or combinations thereof.

4. The method of any of Claims 1-3, wherein the hydrogel or hydrogel microparticle comprise or are treated in the presence of at least one absorbable solvent selected from water, water-compatible alcohols, or combinations thereof.

5. A method for preparing a siloxane composition comprising reacting a mixture comprising:

a. an unsaturated organopolysiloxane;

b. a hydrosilylation catalyst;

c. a hydrogel or hydrogel microparticle whose surface has been modified by an organopolysiloxane or silane through a free radical-initiated encapsulation process utilizing an organoborane initiator to form at least one siloxane-coated surface on the hydrogel or the hydrogel microparticle;

d. optionally a SiH functional organopolysiloxane;

e. optionally a water-soluble active ingredient; and

f. optionally a surfactant.

6. The method of Claim 5, wherein the hydrogel or hydrogel microparticle is selected from gelatin, methylcellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, polyethylene oxide, polyacrylamides, polyacrylic acid, polymethacrylic acid, salts of polyacrylic acid, salts of polymethacrylic acid, poly(2-hydroxyethyl methacrylate), polylactic acid, polyglycolic acid, polyvinylalcohol, polyanhydrides such as poly(methacrylic) anhydride, poly(acrylic) anhydride, polysebacic anhydride, collagen, hyaluronic acid-containing polymers such as poly(hyaluronic acid), polypeptides, dextran, dextran sulfate, chitosan, chitin, agarose gels, fibrin gels, soy-derived hydrogels and alginate-based hydrogels such as poly(sodium alginate), and combinations thereof.

7. A method of Claim 5 or Claim 6, wherein the organopolysiloxane of component (c) comprises an acrylate-functional organopolysiloxane or a methacrylate-functional organopolysiloxane.

8. A composition of any of Claims 5-7, wherein the silane of component (c) comprises an acrylate-functional silane or methacrylate-functional silane.

9. The method of any of Claims 5-8, wherein the hydrogel or hydrogel microparticle is treated in the presence of oxygen with (i) at least one free-radical polymerizable compound that is immiscible with water, water-compatible alcohols, or combinations thereof and (ii) at least one organoborane free-radical initiator.

10. The method of Claim 9, wherein the at least one organoborane free-radical initiator is selected from triethylborane-propanediamine, triethylborane-butylimidazole, triethylborane- methoxypropylamine, tri-n-butyl borane-methoxypropylamine, triethylborane-aminosilane, triethylborane-aminosiloxane complexes and complexes thereof.

1 1 . The method of any of the preceding claims, further comprising heating the siloxane composition to a temperature ranging from about 15°C to about 225°C to effect curing and produce a cured siloxane composition.

12. A method for treating a wound comprising applying the cured siloxane composition of Claim 1 1 to a skin surface or incorporating the cured siloxane composition into a human.

13. The method of any of the preceding claims, wherein the water-soluble active ingredient is selected from a personal care active ingredient, a healthcare active ingredient, an agricultural active ingredient, or combinations thereof.

14. The method of any of the preceding claims, wherein the siloxane composition upon cure is in the form of a gel, a pressure sensitive adhesive, a liquid silicone rubber, a high consistency silicone elastomer, a silicone adhesive, a silicone sealant, or a silicone encapsulant.

15. The method of any of the preceding claims, wherein the siloxane composition upon cure is used in a wound dressing, a wound care material, a transdermal patch, or a drug delivering medical device.

16. A siloxane composition produced by the method of any of the preceding claims.