Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/12—Organo silicon halides
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/12—Organo silicon halides
  • C07F7/121—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20
  • C07F7/123—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20 by reactions involving the formation of Si-halogen linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
  • C07F7/1872—Preparation; Treatments not provided for in C07F7/20
  • C07F7/1892—Preparation; Treatments not provided for in C07F7/20 by reactions not provided for in C07F7/1876 - C07F7/1888
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/06—Preparatory processes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups

Definitions

• isomeric impurities lead to non-homogeneity in copolymer structures and inert impurities may lead to extractable species which may affect biocompatibility or result in domain separation that affects the optical properties of copolymers.
• Polysiloxane macromers are formed by living anionic ring-opening polymerization (AROP). This chemistry is described by Goff et al. (see “Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization,” Molecules, 26, 2755 (2021)). The conditions for avoiding redistribution reactions during the polymerization that forms the siloxane-containing macromer are critical for achieving purity, but most of these variables are now understood. The most significant limit to achieving high- purity is the “end-capper” or “termination” reagent employed in the AROP reaction: 3- (methacryloxy)propyldimethylchlorosilane, having formula (4).
• This end-capper material is conventionally produced by the hydrosilylation of allyl methacrylate.
• the earliest discrete synthesis for the product was reported by Cameron (Polymer, 26, 437 (1985)) in 50% yield with final purity unspecified.
• Cameron Polymer, 26, 437 (1985)
• a major byproduct is the P-isomer, l-methyl-2-methacryloxy ethyldimethylchlorosilane, (formula (5)).
• the genesis of these impurities is the selectivity of the hydrosilylation catalyst which, although favoring the anti-Markovnikov addition product, also allows the formation of the normal Markovnikov product, allows minor dehydrogenative coupling reactions, and catalyzes hydrogenation of the double bond of the acrylate.
• the hydrosilylation is preferred, but not limited to the allylic group, and, to a lesser degree, also occurs with the unsaturation of the acrylate.
• there is allylic unsaturation in the product formed by hydrosilylation of the acrylate double bond under normal polymerization conditions it is essentially unreactive with the consequence that macromers derived from this byproduct are also extractable.
• allyl functional macromers do not readily undergo photoinitiated polymerization.
• JP 2003-096086 of Nishiwaki describes the use of an iridium catalyst, which also resulted in a purity of 98.8%.
• isobutyroxypropyldimethylchlorosilane also known as a-methylpropionyloxypropyldimethylchlorosilane
• all of the earlier literature reports of high purities are likely overstated, at least because at the time of these references, analytical limitations typically lacked the sensitivity to determine hydrogenated and isomeric byproducts and failure to meet performance criteria appeared inexplicable.
• an acryloxyalkyldimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1 wt. % hydrogenated byproducts and less than about 0.1 wt. % isomeric byproducts.
• a method of synthesizing a high purity acryloxyalkyldimethylchlorosilane comprising:
• a methacrylate-functional macromer or copolymer derived from an acryloxyalkyldimethylchlorosilane wherein the macromer or copolymer has a purity of at least about 99%.
• Embodiment 1 An acryloxyalkyldimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1 wt. % hydrogenated byproducts and less than about 0.1 wt. % isomeric byproducts.
• Embodiment 2 The acryloxyalkyl dimethylchlorosilane according to embodiment 1, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.05 wt. % hydrogenated byproducts and less than about 0.05 wt. % isomeric byproducts.
• Embodiment 3 The acryloxyalkyldimethylchlorosilane according to embodiment 1 or 2, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxy alkyl dimethylchlorosilane.
• Embodiment 4 The acryloxyalkyldimethyl chlorosilane according to embodiment 3, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.05 wt. % isobutyroxypropyldimethylchlorosilane and less than about 0.05 wt. % l-methyl-2- methacryloxy ethyldimethylchlorosilane.
• Embodiment 5 The acryloxyalkyldimethyl chlorosilane according to any of the preceding embodiments, wherein the purity is greater than about 99.3%.
• Embodiment 6 The acryloxyalkyl dimethylchlorosilane according to any of the preceding embodiments, wherein the acryloxyalkyldimethylchlorosilane is 3- methacryloxypropyldimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3 - (acryloxy)propyldimethylchlorosilane, 11 -(methacryloxy )undecyldimethylchlorosilane, or 3- (methacryloxy)propylmethyl dichlorosilane.
• Embodiment 7 A method of synthesizing a high purity acryloxyalkyldimethylchlorosilane comprising:
• Embodiment 8 The method according to embodiment 7, wherein step (a) is a phase transfer catalyzed reaction.
• Embodiment 9 The method according to embodiment 7 or 8, wherein step (a) comprises (i) reacting a halide salt with methacrylic acid to form the acrylate salt; and (ii) reacting the acrylate salt with the haloalkyldimethylalkoxysilane.
• Embodiment 10 The method according to any of embodiments 7-9, wherein step (b) is an exchange or substitution reaction.
• Embodiment 11 The method according to any of embodiments 7-10, wherein step (b) comprises reacting the acryloxy-substituted alkyldimethylalkoxysilane with an acetyl chloride and a weak Lewis acid catalyst.
• Embodiment 12 The method according to any of embodiments 7-11, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and the product of step (a) is a (meth)acryloxyalkyldimethylalkoxysilane.
• Embodiment 13 The method according to any of embodiments 7-12, wherein the acryloxyalkyldimethylchlorosilane is 3 -methyacryloxypropyl dimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11- (methacryloxy)undecyldimethylchlorosilane, or 3- (methacryloxy)propylmethyl dichlorosilane.
• the acryloxyalkyldimethylchlorosilane is 3 -methyacryloxypropyl dimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11- (methacryloxy)undecyldimethylchlorosilane, or 3- (methacryloxy)propylmethyl dichlorosilane.
• Embodiment 14 The method according to any of embodiments 7-13, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99%.
• Embodiment 15 The method according to any of embodiments 7-14, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99.3%.
• Embodiment 16 The method according to any of embodiments 7-15, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.1 wt. % hydrogenated byproducts and less than about 0.1 wt. % isomeric byproducts.
• Embodiment 17 The method according to any of embodiments 7-16 wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.05 wt. % hydrogenated byproducts and less than about 0.05% isomeric byproducts.
• Embodiment 18 The method according to any of embodiments 7-17, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and contains less than about 0.05 wt. % isobutyroxypropyldimethylchlorosilane and less than about 0.05 wt. % l-methyl-2-methacryloxy ethyldimethylchlorosilane.
• Embodiment 19 A method for synthesizing a high purity (meth)acryloxyalkyldimethyl functional polysiloxane macromer comprising performing living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as a starting material and the acryloxyalkyldimethylchlorosilane according to any of embodiments 1-6 as a termination reagent.
• Embodiment 20 The method according to embodiment 19, wherein the polysiloxane is a monomethacryloxypropyl terminated polydimethylsiloxane.
• Embodiment 21 The method according to embodiment 19 or 20, wherein the polysiloxane is substantially free of non-polymeric polysiloxanes.
• Embodiment 22 The method according to any of embodiments 19-21, wherein the polysiloxane contains less than about 0.1 wt. % impurities containing hydrogenated derivatives or isomers of the (meth)acryloxyalkyl functionality.
• Embodiment 23 A methacrylate-functional macromer or copolymer derived from an acryloxyalkyldimethylchlorosilane, wherein the macromer or copolymer has a purity of at least about 99%.
• Embodiment 24 The macromer or copolymer according to embodiment 23, wherein the macromer or copolymer contains less than about 0.1 wt. % hydrogenated derivatives of the methacrylate functionality.
• Embodiment 25 The macromer or copolymer according to embodiment 23 or 24, wherein the macromer or copolymer contains less than about 0.05 wt. % hydrogenated derivatives of the methacrylate functionality.
• Embodiment 26 The macromer or copolymer according to any of embodiments 23-25, having a molecular weight of less than about 5,000 Daltons.
• Embodiment 27 The methacrylate-functional macromer or copolymer derived from an acryloxyalkyl dimethylchlorosilane according to any of embodiments 23-26, wherein the macromer or copolymer has a purity of at least about 99.3%.
• the disclosure relates to a method for synthesizing high purity acryloxyalkyldimethylchlorosilanes, which are suitable end-cappers for living AROP. These high purity compounds are substantially free of isomers and hydrogenated byproducts and allow for the preparation of high purity acryloxyalkyl terminated poly(siloxanes) which are substantially free of non-polymerizable poly siloxanes.
• the method of this disclosure avoids hydrosilylation of an acrylate, and instead utilizes substitution reactions in which there is no chemical mechanism for isomerization or reduction.
• the endcapper produced by the method is 3-methacryloxypropyldimethylchlorosilane (formula (4)) with a purity of about 99% or greater and contains no detectable hydrogenated analog (isobutyroxypropyldimethylchlorosilane, having formula (6)) or the 0-isomer (l-methyl-2- methacryloxyethyldimethylchlorosilane, having formula (5)).
• This high purity compound may be used as an end-capper or terminator for the production of monomethacryloxypropyl terminated poly dimethylsiloxanes.
• high purity compounds suitable as endcappers or termination reagents for the living AROP synthesis of macromers which may be synthesized by the method described herein include (methacryloxymethyl)dimethylchlorosilane and 3-(acryloxymethyl)dimethylchlorosilane, which have not heretofore been synthesized.
• the compounds described herein are substantially free of isomeric and hydrogenated byproducts/reductive analogs.
• the negative effects of impure end-capping compounds are most significant when the macromers are of relatively low molecular weight, in particular less than about 5,000 Daltons.
• the non-reactive macromers formed from reductive analogs can be solubilized in a final polymer in which the macromer forms a pendant group in a copolymer.
• copolymers derived from low molecular weight macromers With copolymers derived from low molecular weight macromers, a loss of optical transmission caused by phase separation of the reductive analog may occur.
• the materials and methods described herein solve the problem of defects in optics which are associated with low molecular weight macromers incorporated as comonomers in polymers utilized in the formation of contact lenses.
• the term “high purity” may be understood to mean a purity greater than about 99%, more preferably greater than about 99.2 %, even more preferably greater than about 99.3%.
• the term “substantially free” may be understood to mean that the impurity is not detectable by GC and GC-MS, which typically have detection limits of less than about 0.05 wt. %. Accordingly, the method provides for the synthesis of acryloxyalkyldimethylchlorosilanes having high purity and also no detectible isomeric or hydrogenated byproducts, that is, less than about 0.1 wt. % or less than about 0.05 wt. % isomeric or hydrogenated byproducts. Other impurities which may be present will have little impact on AROP or in the performance of the resulting macromers.
• the method for synthesizing the high purity acryloxyalkyldimethylchlorosilanes involves (a) forming an acryloxy-substituted alkyldimethylalkoxysilane, preferably by a phase transfer catalyzed reaction between an acrylate salt and a (haloalkyl)dimethylalkoxysilane, and then (b) displacing the alkoxy group with a halide, preferably in an exchange or substitution reaction.
• a preferred acrylate salt is potassium methacrylate, which may be generated in-situ from the reaction of potassium carbonate and methacrylic acid, for example.
• a preferred (haloalkyl)dimethylalkoxysilane is 3-chloropropyldimethylethoxysilane.
• an acrylic acid may be reacted with a haloalkylsilane in the presence of a base acceptor.
• this chemistry cannot directly produce the preferred methacryloxypropyldimethylchlorosilane because the acrylate salt also reacts with the chlorine bound to silicon.
• the high purity end-capper is a (meth)acryloxypropyldimethylchlorosilane and the intermediate is a (meth)acryloxypropyldimethylethoxysilane.
• an ethoxy group on silicon may be exchanged with chlorine by reaction with thionyl chloride, phosphoryl trichloride, phosphorous pentachloride, benzyl chloride, boron trichloride, tin tetrachloride, methyltrichlorosilane, or an acid chloride, among others.
• thionyl chloride and phosphorus pentachloride may additionally cleave acrylate esters, forming acid chlorides, and all act as initiators for polymerization (see T. Sengupta et al, Journal of the Indian Chemical Society, 53:7, 726-7 (1976)).
• Benzyl chloride and acid chlorides are less effective in exchange or substitution reactions unless catalyzed by the presence of a strong Lewis acid type catalyst such as aluminum trichloride or boron trichloride.
• strong Lewis acids have the potential to catalyze reactions involving the acrylate functionality.
• a presently preferred reaction couple for the exchange reaction is acetyl chloride and a weak Lewis acid catalyst, preferably ferric chloride, which does not cleave the acrylate ester or induce polymerization.
• a weak Lewis acid catalyst preferably ferric chloride
• the synthetic method described above is generally applicable for producing analogs and homologs of 3 -methacryloxypropyldimethylchlorosilanes in purities greater than about 99%, more preferably greater than about 99.2 %, even more preferably greater than about 99.3%, without detectable isomers or hydrogenated byproduct contamination, and which are suitable for use in the synthesis of high purity acrylate functional macromers.
• aspects of the disclosure also relate to methods for producing high purity (meth)acryloxyalkylmethylsiloxane macromers and copolymers derived from the high purity (meth)acryloxyalkylmethyldichlorosilanes described above.
• Asymmetric macromers are typically prepared by initiating polymerization with a lithium dimethylsilanolate formed by the reaction of an alkyl lithium reagent with a strained cyclic siloxane, most commonly hexamethylcyclotrisiloxane.
• the lithium silanolate can be isolated or formed in situ.
• a strained cyclic with a promoter typically an aprotic polar material such as dimethylformamide or tetrahydrofuran
• a chlorosilane such as the most commonly used 3 -(methacryloxy)propyldimethyl chlorosilane
• These macromers and copolymers have a purity of greater than about 99%, more preferably greater than about 99.2 %, even more preferably greater than about 99.3%, contain less than about 0.1 wt. % hydrogenated impurities and less than about 0.1 wt. % isomeric impurities, and have a molecular weight less than about 5,000 Daltons, more preferably less than about 1,000 Daltons.
• Further aspects of the disclosure relate to methods for producing high purity (meth)acrylate functional macromers derived from the high purity end-cappers, including meth(acryloxy)methyl terminated macromers which have not been previously prepared. Specifically, these macromers may be produced using AROP procedures which are well known in the art and employing the high purity end-cappers described herein.
• a method for synthesizing a high purity (meth)acryloxyalkyl dimethyl functional asymmetric polysiloxane macromer comprises performing living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as a starting material and the acryloxyalkyldimethylchlorosilane as previously described as an end-capper.
• the polysiloxane is a monomethacryloxypropyl terminated polydimethylsiloxane.
• the resulting polysiloxane is substantially free of non-polymeric polysiloxanes and contains less than about 0.1 wt. % impurities (or less than about 0.05 wt.
• symmetric polysiloxane macromers may be derived from 3-(methacryloxypropyl)methyldichlorosilane.
• Phenothiazine (5 wt %) was added to the reaction mixture and purified using a wiped film evaporator to afford a clear colorless liquid (1100 g, 50 %).
• FTIR (cm' 1 ): 2958.43, 2925.56, 2892.7, 1716.86, 1638.17, 1452.32, 1407.43, 1319.71, 1295.06, 1254.91, 1157.04, 1064.03, 1011.38, 938.82, 846.93;
• GC-TCD purity - 88.85%, P-isomer - 2.01%, isobutyroxypropyldi
• a 2L 4-neck flask was equipped with a mechanical stirrer, heating mantle, addition funnel, pot thermal probe, fritted glass dispersion tube and Dean-Stark trap with water-cooled condenser.
• Di-t-butylhydroxytoluene (BHT) (4.19g, 3.50 wt%) and toluene (960 g) were charged to the reactor. Stirring was initiated and potassium carbonate (109.1 g, 7.67 mol) was added. The slurry was heated to 80°C with an Cb/Ar sparge and then methacrylic acid (119.9 g, 1.40 mol) was added dropwise at 100°C over 2 hours.
• the product was then purified by wiped film evaporation at 0.6-0.7 mmHg vacuum, with a 64-5°C jacket temperature and a cold finger temperature of 30°C with a product residue split of 4: 1 to afford the final product, 3- methacryloxypropyldimethylethoxysilane, as a clear colorless liquid (202.6 g, 66.2 %).
• a IL 4-neck reactor was equipped with a magnetic stirrer, pot thermal probe, cooling bath, addition funnel, packed column, and distillation head with N2.
• Ferric chloride, anhydrous, (1.40 g, 0.01 mol) and acetyl chloride (123.6 g, 1.58 mol) were charged to the reactor.
• 3 -Methacryloxypropyldimethylethoxy silane as prepared in Example 2 inhibited with 1 wt % BHT (345.5 g, 1.50 mol) and phenothiazine (1.50 g, 0.01 mol) were added dropwise to the reaction mixture at a rate to maintain the reaction temperature at 20 to 25°C.
• a 22 L 4-neck flask was equipped with a mechanical stirrer, heating mantle, addition funnel, pot thermal probe, fritted glass dispersion tube and distillation head mounted on a 500 cm packed column.
• the flask was charged with 3000 ml of cyclohexane and 3718 g of a solution of 32% potassium methoxide in methanol. Stirring and a below liquid surface air sparge were initiated.
• Methacrylic acid 1439 ml, inhibited with BHT was added through an addition funnel, maintaining the temperature below 60°C. After addition was completed, the pH was >9. The flask was then heated to remove methanol.
• the polymer was terminated with 3 -methacryloxypropyldimethylchlorosilane (prepared in Example 3) to obtain monobutyl-, monomethacryloxypropyl-terminated polydimethylsiloxane.
• the solution was then stirred overnight and washed with 178 g deionized water.
• the aqueous and organic layers were separated, and the organic layer was dried with sodium sulfate, filtered, and stripped under vacuum at 95°C with a dry air sparge.
• 3-Methacyloxpropyldimethylchlorosilane was synthesized as described in Example 1 of U.S. Patent No. 5,493,039 of Okawa using the same conditions and scale, except that the water content of the allyl methacrylate was 37 ppm and not 171 ppm. Analysis of the product revealed the presence of isobutyroxypropyldimethylchlorosilane (0.59 %) and the 0-isomer (1.47%). The purpose of this comparative example was to demonstrate that, although not reported by Okawa, the reduction product was in fact generated during this hydrosilylation method. The level of isobutyroxymethyldimethylchlorosilane was below the level of detection by GC and GC-MS using a capillary column, i.e., less than 0.05%
• the 3-methacryloxypropyldimethylchlorosilane prepared by the method according to the present disclosure not only has dramatically higher purity than the analogous material prepared by traditional hydrosilylation, but also has no detectable 0-isomer or hydrogenated byproduct. Further, the percentage excess required when using this compound as an end-capper for AROP is reduced by half.

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