WO2019172850A1

WO2019172850A1 - A porous polymeric matrix and the use of the same

Info

Publication number: WO2019172850A1
Application number: PCT/SG2019/050127
Authority: WO
Inventors: Xinwei Chen; Wui Siew Tan; Shu Mei Man; Yosephine ANDRIANI; Chao Chen; Benzhong Wang
Original assignee: Agency For Science, Technology And Research
Priority date: 2018-03-06
Filing date: 2019-03-06
Publication date: 2019-09-12

Abstract

The present invention relates to porous polymeric matrix comprising a plurality of cross-linked acrylate monomers and the use of the same. The present invention also provides a method for releasing a plurality of the fragrance molecules, comprising the steps of: i) providing a porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm; and ii) loading the porous polymeric matrix with the plurality of the fragrance molecules.

Description

A Porous Polymeric Matrix and The Use of

The Same

Cross-Reference to Related Application

This application claim priority to Singapore application number 10201801846Q filed on 6 March 2018, the disclosure of which is hereby incorporated by reference.

Technical Field

The present invention generally relates to a porous polymeric matrix. In particular, the present invention relates to a porous polymeric matrix comprising a plurality of cross- linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm. The present invention is also directed to a method for controlled release of fragrances using the polymeric matrix as defined herein.

Background Art

Sustained and prolonged delivery of low molecular weight volatile materials including fragrance, perfume, deodorants, and insecticides remains challenging. The controlled and extended delivery of small volatile molecules such as sustained fragrance evolution or insect repellency in the environment is necessary and desirable for creating long lasting performance.

Broadly, fragrance may consist of top, middle and base notes. Such notes are classified based on their vapour pressure. The vapour pressures of top, middle and base notes are >0.13 mbar (>13 Pa), between 0.04 and 0.13 mbar (between about 4 and 13 Pa) and <0.04 mbar (<4 Pa), respectively. Top notes are in general highly valued by consumers due to the perceived "freshness" and "assertiveness". However, top notes tend to evaporate quickly (usually less than a few hours) and results in the reduced intensity and / or the change in flavour of the fragrance (this is often regarded as perceived degradation by consumer). The methods currently used to minimize the above issue include pro-fragrance, encapsulation, polymeric material and gel techniques.

The pro-fragrance technique requires the volatile fragrance to be covalently bound to a substrate or non-volatile precursor molecule to obtain a non-volatile compound. The fragrance molecules are only released upon external stimuli, which selectively cleaves the covalent bonding between the fragrance and non-volatile molecule; for instance, exposure to moisture. Another stringent requirement is that the fragrance molecules must have functional group that is able to bind the substrate or non-volatile precursor molecule such as aldehydes or ketones. Overall, the pro-fragrance technique is costly and lacks of scalability.

Another method to contain the fragrance and thereby to reduce the loss of fragrance is via an encapsulation method, which can be regarded as a shell-design, where the shell acts as a physical barrier for the encapsulated fragrance. The encapsulation technique consists of firstly forming a stabilized fragrance in aqueous medium followed by synthesizing the shell with techniques, which may include microfluidic and/or interfacial polymerization. However, in most cases, the shell cannot effectively contain the fragrance with molecular weight <300 Da, leading to a significant loss of fragrance during storage. Additionally, since the fragrances are usually amphiphilic, they exhibit partial solubility in the solvent, resulting in a substantial loss during the fabrication process of emulsifying the fragrance in aqueous medium.

A further method to control the release of fragrance is via a polymeric material technique, whereby polymers are usually added as part of the composition to the products such as hand cream and shampoo. Fragrances are loaded into the polymer during the synthesis process to control their release compared to directly loading them into the product. In another design, polymeric matrix, which is typically thermoplastic, has been used to control the release of fragrance. However, thermoplastics are not able to release different components of the volatile materials with different volatilities uniformly.

Still a further method to reduce the release of fragrance is via a gel method to contain the fragrance within a gel matrix. However, similar to the encapsulation technique counterpart, this method is ineffective to control the release of fragrance having molecular weight of less than 300 Da. Further, both encapsulation and gel methods offer little or no differentiation to the evaporation rate of various notes. Additionally, both techniques are generally difficult to mould to various permanent shape.

In light of the above, the present invention therefore provides a porous polymeric matrix used for sustained or controlled release of fragrance that overcomes, or at least ameliorates, one or more of the disadvantages described above.

Summary

In one aspect, there is provided a porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm.

Advantageously, the porous polymeric matrix described herein may be easily shaped and thus may be suitable for use in an additive manufacturing (or 3D printing). Further advantageously, the polymeric matrix as defined herein may have a rigid, non-reactive structure having low swelling property.

Yet advantageously, the porous polymeric matrix of the present disclosure may be reused as it is able to retain its structure integrity over a period of time of usage. Still advantageously, the porous polymeric matrix as defined in the present disclosure may be clear and transparent thus broadening potential applications of said porous polymeric matrix.

In another aspect, there is provided use of a porous polymeric matrix for a controlled release of the plurality of fragrance molecules, wherein the porous polymeric matrix comprises a plurality of cross-linked acrylate monomers, and wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 n .

Advantageously, the polymeric matrix as defined herein when used to release the plurality of fragrance molecules may be able to significantly reduce the evaporation rate of the fragrance molecules. When desired, a prolonged and sustained release of the plurality of fragrance molecules may be achieved by way of varying the substituents found in the polyurethane acrylate repeat units as defined herein, the length of the repeat units and / or the length of the chain of cross-linkers.

The controlled release of the plurality of the fragrance molecules herein may be associated with the degree of cross-linking occurred in the polymeric matrix. The degree or extent of the cross- linking mentioned may depend on the type of substituents of the polyurethane acrylate repeat units as defined herein, the length of the repeat units, and / or the length of the chain of cross linkers.

In another aspect, there is provided a method for releasing a plurality of the fragrance molecules, comprising the steps of:

i) providing a porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm; and

ii) loading the porous polymeric matrix with the plurality of the fragrance molecules.

Advantageously, the step of providing the porous polymeric matrix as defined herein may be of low cost.

Further advantageously, the step of providing the porous polymeric matrix as defined above may be achieved at a relatively short period of time since the polymerization process occurs rapidly.

Definitions

The following words and terms used herein shall have the meaning indicated:

"Alkyl" as a group or part of a group refers to a straight or branched aliphatic hydrocarbon group, preferably a -C₅₀ alkyl, preferably a C ₁ C ₁₂ alkyl, more preferably a - o alkyl, most preferably -C₆ unless otherwise noted. Examples of suitable straight and branched Ci-C₆ alkyl substituents include methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, t-butyl, hexyl, and the like. The group may be a terminal group or a bridging group.

"Alkenyl" as a group or part of a group denotes an aliphatic hydrocarbon group containing at least one carbon-carbon double bond and which may be straight or branched preferably having 2-12 carbon atoms, more preferably 2-10 carbon atoms, most preferably 2-6 carbon atoms, in the normal chain. The group may contain a plurality of double bonds in the normal chain and the orientation about each is independently E or Z. Exemplary alkenyl groups include, but are not limited to, ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl and nonenyl. The group may be a terminal group or a bridging group.

"Alkynyl” as a group or part of a group means an aliphatic hydrocarbon group containing a carbon-carbon triple bond and which may be straight or branched preferably having from 2-12 carbon atoms, more preferably 2-10 carbon atoms, more preferably 2-6 carbon atoms in the normal chain. Exemplary structures include, but are not limited to, ethynyl and propynyl. The group may be a terminal group or a bridging group. As used herein, the term“alkanediyl” refers to a non-aromatic divalent group, wherein the alkanediyl group is attached with two s-bonds, with one or two saturated carbon atom(s) as the point(s) of attachment, a linear or branched, cyclo, cyclic or acyclic structure. The term “alkanediyl” as defined herein, does not include carbon-carbon double or triple bonds, and does not have atoms other than carbon and hydrogen. The groups,— CH_2— (methylene), — CH₂CH_2— ,— CH₂C(CH₃) CH_2— ,— CH₂CH₂CH_2— or— CH₂CH₂CH₂CH_2— are non limiting examples of alkanediyl groups.

"Halogen" represents chlorine, fluorine, bromine or iodine.

The term“optionally substituted” as used herein means the group to which this term refers may be unsubstituted, or may be substituted with one or more groups independently selected from alkyl, alkenyl, alkynyl, halogen, haloalkyl, haloalkenyl, haloalkynyl, alkynyloxy, hydroxyl, hydroxyalkyl, alkyloxy, alkyloxyalkyl, aryl, heteroaryl, arylalkyl.

“Repeat unit or repeating unit” used in the present disclosure refers to a part of polymer whose repetition would produce the complete polymer chain (except the end-groups) by linking or binding the repeat units together successively.

As used herein the term“fragrance composition” refers to an aromatic compound or a mixture of aromatic compounds including, for example, natural oils, synthetic oils, alcohols, aldehydes, ketones, esters, lactones, and frequently hydrocarbons which are admixed so that the combined odours of the individual components produce a pleasant or desired fragrance. Such fragrance composition usually contains (a) the main note or the bouquet or foundation-stone of the composition, (b) at least one modifier which rounds off and accompany the main note, (c) at least one fixative which includes odorous substances which lend a particular note to the composition throughout all stages of evaporation, and substances which retard evaporation, and (d) top notes which are usually low-boiling fresh-smelling materials. The fragrance composition as defined herein can be used in conjunction with carriers, vehicles, solvents, dispersants, emulsifiers, surface-active agents, aerosol propellants and the like.

In the fragrance composition as defined above, the individual components contribute their particular olfactory characteristics. However, the overall effect of the fragrance composition will be the sum of the effect of each ingredient.

The fragrant ingredient may be a naturally occurring essential oil, such as rose oil, bergamot oil, jasmine oil, peppermint oil, rosemary, camomile, lavender, marjoram, and the like oil. An animal fragrant, is for example musk, castoreum, amber or zibet.

Synthetic fragrant ingredients refer to synthetic essential oils, such as composed of single compounds, such as linalol, cineol, terpineol, nerol, citronelal, benzaldehyde, cinnamon aldehyde, vanillin, methylacetophenone, and mixtures thereof. The fragrance composition may have, in addition to the desired pleasant smell, disinfectant activities, such as desirable in room sprays for hospitals, kitchens and toilettes, in water or also in mouth or nose sprays. The disinfectant effect may be directed against any microorganisms, such as virus, bacteria or yeasts.

Disinfectant fragrance may comprise a synergistic mixture of disinfectant essential oils, in particular of natural sources, such as of eucalyptus (Eucalyptus globulus or Eucalyptus citriadora), pine needles (picca excelsa), Ho-leaves (Cinnamomum camphora hosch), peppermint (Mentha piperita), neem tree (Azadirachta excelsa), bay leaves (Laurus nobilis), litsea (Litsea cubeba), citronella (Cymbopogon nardus), elemi (Canarium luzonicum), petitgrain citronniers lemon (Citrus limonum), grapefruit (Citrus paradisi), fir tree (Abies alba pectinata), lavender (Lavandula officinalis), bergamotte (Citrus aurantium bergamia), rosemary (Rosmarinus officinalis), and mixtures thereof.

The fragrance composition may also have a therapeutic effect as known in aromatherapy. Well known are stimulating, antidepressive or narcotic effects of certain fragrance compositions. In this case, it comprises one or more essential oils, in particular of natural origin and having the desired therapeutic effect. Such fragrance compositions may be applied in form of room, air, mouth or nose sprays.

The fragrance compositions may also have an insect or marten repellent effect or be useful in plant protection.

The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the invention.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.5% of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Detailed Disclosure of Embodiments

Exemplary, non-limiting embodiments of a porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm will now be disclosed. There is provided a porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm.

The acrylate monomers may be polyurethane acrylate or PUA monomers (unless specified otherwise, the terms“polyurethane acrylate” and“PUA” may be used interchangeably). The acrylate monomers may be cross-linked by a cross-linker. The cross-linker may be an acrylate- based cross-linker.

Therefore, in an exemplary embodiment, when the acrylate monomers are polyurethane acrylate monomers, said porous polymeric matrix comprises a plurality of cross-linked polyurethane acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm. In another exemplary embodiment, there is provided a porous polymeric matrix comprising a plurality of cross-linked polyurethane acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm and wherein the cross-linker is an acrylate -based cross-linker.

The polyurethane acrylate monomer as defined herein may have a structure shown as formula

(I):

wherein R_l R₂, R ; and R₄ are each independently selected from an optionally substituted C i ₂₀alkyl such as optionally substituted Q alkyl, C₂alkyl, C₃alkyl, C₄alkyl, Csalkyl, Cnalkyl, C₇alkyl, C₈alkyl, C₉alkyl, C₁₀alkyl, C_nalkyl, C₁₂alkyl, C₁₃alkyl, C₁₄alkyl, C₁₅alkyl, C₁₆alkyl, Cnalkyl, Ci₈alkyl, Cnalkyl or C₂₀alkyl and a moiety of formula (II) shown below,

wherein

R₅ is absent or optionally substituted C _{| 3}alkancdiyl, where the optionally substituted C _| ₅alkanediyl includes alkanediyl, C₂alkanediyl, C₃alkanediyl, C₄alkanediyl and C₅alkanediyl; o is an integer selected from 0, 1, 2, and 3; R₆, R7, Rg, R9 are each independently selected from the group consisting

wherein R_a is optionally substituted Ci_₅alkyl such as optionally substituted alkyl, C₂alkyl, C₃alkyl, C₄alkyl or Csalkyl;

n is an integer selected from 0, 1, 2, 3 and 4;

p is an integer selected from 0, 1, 2 and 3;

m is an integer selected from 0, 1, 2, 3, 4, 5 and 6; and

with the proviso that at least one of the R_{l 5} R₂, R3 or R4 is the moiety of formula (II); and wherein ( ^JVW' ) indicates the point of attachment of R₆, R7, Rg and R₉ in the moiety of formula (II).

In an exemplary embodiment, the polyurethane acrylate repeat units may have the structure as shown below:

The plurality of acrylate -based cross-linkers as defined herein may have a structure as shown in Formula (III)

wherein:

R₁₃ is optionally substituted C_{1 5}alkyl such as optionally substituted C_| alkyl, C₂alkyl, C₃alkyl,

C₄alkyl or Csalkyl;

x, y and z are each independently an integer selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

The sum of x, y and z may be 3, 9 or 20.

The acrylate -based cross-linkers may be selected from:

or

wherein x, y and z are as defined above.

Here, the porous polymeric matrix may further comprise a second polyurethane acrylate monomer. When said polymeric matrix comprises the second polyurethane acrylate monomers, the polyurethane acrylate monomers previously defined as component a) may be referred as the first polyurethane acrylate monomers. The second polyurethane acrylate monomers as defined herein may have the longer or shorter length as compared to the first polyurethane acrylate monomers. Preferably, the second polyurethane acrylate monomers may have a shorter length as compared to the first polyurethane acrylate monomers. When the second polyurethane acrylate monomers form part of the porous polymeric matrix, said second polyurethane acrylate monomers may be cross-linked. Similar as mentioned above, the cross-linker may be acrylate- based cross-linkers.

The second polyurethane acrylate monomers may have the same or different general structure as the first polyurethane acrylate monomers. The second polyurethane acrylate monomers may be pentaerythritol tetraacrylate (PET A), where its structure thereof is represented by the following formula:

In an exemplary embodiment, the porous polymeric material of the present disclosure may comprise:

a) a first polyurethane acrylate monomer of the following structure:

; and b) a second polyurethane acrylate monomer, wherein said second polyurethane acrylate monomer is pentaerythritol tetraacrylate (PET A).

When the second polyurethane acrylate monomers are present, their amount in the polymeric matrix as defined herein may not exceed 30 wt%. Hence, the amount of the second polyurethane acrylate monomers is preferably about 25 wt% or less such as about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 10 wt%, about 15 wt%, or about 20 wt%. More preferably, the amount of the second polyurethane acrylate monomers is less than about 1 wt%, such as about 0.1 wt%, about 0.3 wt%, or about 0.5 wt%. The weight percent here is calculated based on the total weight of the polymeric matrix. It is to be appreciated that said second polyurethane acrylate monomers may be present in any other amounts provided it is lesser than 30 wt% but greater than 0 wt% (since it is understood that 0 wt% indicates the absence of the second polyurethane acrylate monomers).

Yet advantageously, the polymeric matrix as described above may be reused since it is able to retain or substantially maintain its structure integrity over a period of time upon its usage.

Still advantageously, the polymeric matrix as defined in the present disclosure may be clear and transparent.

The polyurethane acrylate monomers and the plurality of acrylate -based cross-linkers as defined herein may be curable. Therefore, when a mixture comprising the polyurethane acrylate monomers and the plurality of acrylate -based cross-linkers as described herein is subjected to a curing process, the porous polymeric matrix as defined above may be produced.

The curing process above may be undertaken in the presence of UV light or via heat treatment. When the curing process is undertaken in the presence of UV light, one or more photoinitiators may be required. Such photoinitiators may be a ketone-based photoinitiator selected from acetophenone (or methyl phenyl ketone), 3-acetophenol (3-hydroxyphenyl methyl ketone), 1- hydroxy-cyclohexyl-phenyl-ketone, 2 -hydroxy -2-methyl-l -phenyl- 1 -propanone, diphenyl ketone, benzoin (2-hydroxy-2-phenylacetophenone), anthraquinone, benzyl (diphenylethanedione) and mixtures thereof. Other ketone-based photoinitiators may be used provided they are suitable for UV curing of the polyurethane acrylate (PUA) monomers as defined herein. When the curing process is undertaken via heat treatment, a thermal initiator may be required. The suitable thermal initiator may be selected from common thermal initiators such as azo compounds, organic peroxides or inorganic peroxides. Non-limiting example of organic peroxides include benzoyl peroxide and tert- butyl peroxide. It is understood other suitable thermal initiators may be used here. Under this curing process, the temperature of the process may be elevated to a curing temperature in which the curing occurs. Such curing temperature may depend on the thermal initiator used in the process.

In the curing process using UV light, heat treatment may optionally be required to initiate the polymerization of the monomers above. Such heat treatment may involve the use of heating or chilling, and it is normally to extreme temperatures, to achieve a desired result such as hardening or softening of the porous polymeric matrix as described herein. The temperature used in such heat treatment may depend on the type of photoinitiator. Heat treatment techniques may include annealing, case hardening, precipitation strengthening, tempering, normalizing and quenching.

The porous polymeric matrix as defined above may be solid-state or substantially solid-state. Hence, said porous polymeric matrix may be formed into different shapes and sizes such as pellets, granules or mixtures thereof.

Prior to the curing process, the monomers solution such as the solution containing polyurethane acrylate monomers as defined above may be applied onto a support and cured thereafter. Upon curing, a membrane or polymeric matrix may then be formed on said support, which may be used for various applications.

The pore diameter of the porous polymeric matrix may be regarded as an average diameter. The pore diameter (or average diameter) of said porous polymeric matrix may be about 30 nm or less, such as about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 15 nm, about 20 nm or about 25 nm. The pore diameter (or average diameter) of said porous polymeric matrix may also be represented as the range from the above values such as about 5 nm to about 6 nm, about 5 nm to about 7 nm, about 5 nm to about 8 nm, about 5 nm to about 9 nm, about 5 nm to about 10 nm, about 5 nm to about 15 nm, about 5 nm to about 20 nm or about 5 nm to about 25 nm. The porous polymeric matrix is then considered to have free volume space therein, which refer to an empty space or substantially empty space between the polymer linkage chains with another corresponding polymer chain. The empty space may then form pores (or channels).

Due to the presence of the channels or pores as above, the polymeric matrix may therefore be considered as a porous matrix.

The pore (or channel) stated above may be of irregular or regular in shape and dimension. When the empty space is in regular shape and dimension, such empty space may have substantially similar shape and dimension throughout the polymeric matrix. For clarity, when the shape of the pore (or channel) is a tube-like, the cross-section area of such pore (or channel) may be substantially uniform across the length of the channel. Exemplary, non-limiting embodiments of a porous polymeric matrix for a controlled release of the plurality of fragrance molecules will now be disclosed.

The present disclosure further provides use of a porous polymeric matrix for a controlled release of the plurality of fragrance molecules, wherein the porous polymeric matrix comprises a plurality of cross-linked acrylate monomers, and wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm.

The porous polymeric matrix for releasing the plurality of fragrance molecules in a controlled manner may be the porous polymeric matrix as defined herein. Therefore, it is to be appreciated that some or all characteristics of said porous polymeric matrix here may be substantially similar or identical to the above.

The porous polymeric matrix for the controlled release of the plurality of fragrance molecules may comprise the polyurethane acrylate or PUA monomers of the following structure:

and the plurality of the acrylate -based cross-linkers having the following formula:

with x, y and z are as defined previously.

The sum of x, y and z may be 3, 9 or 20. The porous polymeric matrix used for the controlled release of the plurality of fragrance molecules as defined above may further comprise a second polyurethane acrylate monomer. Said second polyurethane acrylate monomer may be pentaerythritol tetraacrylate (PET A) with the following structure:

When the second polyurethane acrylate monomers are present in the porous polymeric matrix, its amount may not exceed 30 wt%. Therefore, the amount is preferably about 25 wt% or less such as about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 10 wt%, about 15 wt% or about 20 wt%. More preferably, the amount of the second polyurethane acrylate monomers is less than 1 wt%, such as about 0.1 wt%, about 0.3 wt%, or about 0.5 wt%. The weight percent here is calculated based on the total weight of the polymeric matrix and the fragrance molecules present therein.

The fragrance molecules may form part of a fragrance composition. The fragrance composition may comprise an aromatic compound or a mixture of aromatic compounds. Non-limiting examples of such aromatic compounds include natural oils, synthetic oils, alcohols, aldehydes, ketones, esters, lactones, and frequently hydrocarbons which may be admixed so that the combined odours of the individual components result in a pleasant or desired fragrance.

The aromatic compounds as defined herein may include those having a molecular weight less than 300 Da, such as about 100 Da, about 125 Da, about 150 Da, about 175 Da, about 200 Da, about 225 Da, about 250 Da or about 275 Da. Therefore, it follows that when the plurality of the fragrance molecules is the mixture of the above aromatic compounds, such mixture may therefore also have the average molecular weight less than 300 Da, such as about 100 Da, about 125 Da, about 150 Da, about 175 Da, about 200 Da, about 225 Da, about 250 Da or about 275 Da. The compounds above therefore include those having a molecular weight with the range as indicated above such as from about 100 Da to about 300 Da. It is known to a person skilled in the art that 1 Da is equivalent to 1 g/mol. The fragrance molecule may be benzyl acetate (BA), phenyl ethyl alcohol (PEA), benzaldehyde or other suitable aldehyde -containing organic compounds. Preferred fragrance molecule in the present disclosure is benzyl acetate (BA).

Advantageously, the polymeric matrix as defined herein when used to release the plurality of fragrance molecules may be able to significantly reduce the evaporation rate of the fragrance molecules. When desired, a prolonged and sustained release of the plurality of fragrance molecules may be achieved by varying the substituents R₅ to R₉ of polyurethane acrylate (PUA) repeat units as defined above, the length of the repeat units, and / or the length of the chain of cross-linkers (i.e. x, y and z).

The controlled release as defined above may be release of the plurality of the fragrance molecules at a slower rate or at a slower evaporation rate. The controlled release of the plurality of the fragrance molecules here may therefore relate to the degree of cross-linking occurred in the polymeric matrix. The degree or extent of the cross-linking mentioned above may depend on the following factors

• the type of substituents R₅ to R₉ of the polyurethane acrylate repeat units as defined above;

• the length of the repeat units; and / or

• the length of the chain of cross-linkers (i.e. x, y and z).

Surprisingly, when a small amount of a second polyurethane acrylate repeat unit is added, the release (or evaporation rate) of the fragrance molecule may be further slowed down. This may be due to the structural changes (or conformational changes) of the free volume space in the matrix. Without being bound to theory, a certain adjustment, which results in conformational changes that would decrease the release of the fragrance molecules.

Exemplary, non-limiting embodiments of a method for releasing a plurality of the fragrance molecules will now be disclosed.

The present disclosure also provides a method for releasing a plurality of the fragrance molecules, comprising the steps of:

Advantageously, the step of providing the porous polymeric matrix as defined herein may be regarded as cost-effective.

Further advantageously, the step of providing the porous polymeric matrix as defined above may be achieved at a relatively short period of time since the polymerization process occurs rapidly or almost instantaneously.

The porous polymeric matrix obtained in step i) may be the porous polymeric matrix as defined previously. Therefore, it is to be appreciated that some or all characteristics of said porous polymeric matrix here may be substantially similar or identical to the previously defined characteristics.

Similarly, the plurality of the fragrance molecules present in step ii) above may be the same as the plurality of the fragrance molecules defined previously. Therefore, it is to be understood that some or all characteristics of said plurality of the fragrance molecules here may be substantially similar or identical to the previously defined characteristics.

The loading step as defined above may be undertaken at a temperature in the range of about 40°C to about 90°C, such as about 40°C to about 50°C, about 40°C to about 60°C, about 40°C to about 70°C, about 40°C to about 80°C, about 50°C to about 60°C, about 50°C to about 70°C, about 50°C to about 80°C, about 50°C to about 90°C, about 60°C to about 70°C, about 60°C to about 80°C, about 60°C to about 90°C, about 70°C to about 80°C, about 70°C to about 90°C or about 80°C to 90°C. The loading step as defined above may be undertaken for a period of time from about one hour to 3 days, such as about one hour, about 2 hours, about 5 hours, about 10 hours, about 20 hours, about one day, about 2 days or about 3 days.

Owing to the advantages mentioned here, the porous polymeric matrix described in the present disclosure may be able to overcome the limitations of the materials or methods described in the prior arts.

The polymeric matrix as defined herein displays the advantages as follow:

• the polymeric matrix can be easily shaped and therefore suitable to be used for additive manufacturing (or 3D printing);

• the polymeric matrix has a rigid, non-reactive structure having low swelling property;

• the polymeric matrix claimed can be reused since it is able to retain or substantially maintain its structure integrity over a period of time; and

• the polymeric matrix as defined here is clear and transparent.

Therefore, when used to release the plurality of fragrance molecules, the claimed polymeric matrix is able to substantially reduce the evaporation rate (ER) of the fragrance molecules. If a prolonged and sustained release of the plurality of fragrance molecules is desired, this may be achieved by further varying the substituents R₅ to R₉ of polyurethane acrylate repeat units as defined above, the length of the repeat units, and / or the length of the chain of cross-linkers (i.e. x, y and z).

Brief Description of Drawings

The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

Fig·!

[Fig. 1] is a number of schematic diagrams and a graph illustrating the porous polymeric matrix of the present disclosure and a theoretical model to describe the same. Fig. 1A describes a schematic diagram of the polymeric matrix in the form of resin bulk, where the diffusion pathway provided by the free volume of the polymeric matrix is shown, to control the release of the fragrance molecule. Fig. IB is a theoretical model used to determine the relationship between the driving force and pore diameter of the porous polymeric matrix. Fig. 1C is a graph illustrating the relationship between the driving force of the induced pressure required with the pore diameter using benzyl acetate (BA) as the fragrance molecules, N refers to the number of pores per area and Q is volumetric flow rate (measured in m³/s).

Fig.2

[Fig. 2] is a profile of the evaporation rate (ER) of fragrances, determined for the first two hours, released from PUA-based resins with different cross-linker chain length (3, 9 and 20 cross-linker chain length, respectively). Said PUA-based resins used were in the form of pellets with thickness of 0.6 mm as described in the Example. Note that PUA-P3 refers to PUA-based resins with cross-linker chain length of 3. Three fragrances used in the Example i.e. benzyl acetate (BA) and phenyl ethyl alcohol (PEA).

Fig.3

[Fig. 3] is a number of graphs depicting the weight lost profile of benzyl acetate (BA) for various thicknesses of PUA-based resins. Figs. 3A and 3B illustrate such profile when the PUA-based resins used were in the form of pellets of 0.6 mm and 1.0 mm thick, respectively.

Fig.4

[Fig. 4] is a number of graphs illustrating the evaporation rate (ER, first two hours) shown as dark circles (·) and fragrance loading of benzyl acetate (BA) of P9-PETA (PETA served as second polyurethane acrylate repeat unit) resins with various amount of PETA shown as dark squares ( ).

Fig.5

[Fig. 5] is a number of graphs summarizing the profiles of weight loss of benzyl acetate (BA) for various thicknesses of PUA-based resins, where a small amount of PETA was added.

Fig.6

[Fig. 6] is a graph describing weight change of the PUA-P9 resins (pellets of 0.6 mm thick) with repeated cycling of the loading and unloading of benzyl acetate (BA) .

Fig.7

[Fig. 7] is a photograph of a clear and transparent PUA-P9 resin as described in the Example.

Detailed Description of Drawings

Referring to Fig. 1A, this figure describes a schematic diagram of the polymeric matrix or resin bulk (100) of the present disclosure. As can be seen, a diffusion pathway (101) provided by the free volume (102) of the polymeric matrix or resin bulk of the present disclosure allows the release of the fragrance molecule (103) in controlled manner. The fragrance molecule travels along the diffusion pathway and eventually emerges at the surface of the resin (104) where the fragrance molecule is released. The scale length (r) of the narrow constrictions of the pathways is suitable in influencing the diffusion of the fragrance molecules by referring to Fig. 1C.

Fig. IB depicts a theoretical model used for determining the relationship between the driving force and the pore diameter of the porous polymeric matrix (100). The fragrance molecules (103) are indicated as shown in this figure. The term“d” shown in this figure represents the pore size or pore diameter, which defines the characteristic of the claimed porous polymeric matrix. Examples

Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example: Polyurethane Acrylate (PUA) Resins For Controlled Release of Fragrance

a) Solid-state polymeric matrix

Here, a solid state polymeric matrix comprising UV-curable polyurethane acrylate (PUA) resins was used as a material to control the release of the fragrance. The PUA resin contained aliphatic urethane acrylate (Ebecryl® 265, PUA purchased from Allnex Germany GmbH of Frankfurt am Main, Germany) and trimethylolpropane ethoxy triacrylates with 3, 9 or 20 ethoxy group repeating units (purchased from Cytec Industries, Inc. of Woodland Park, New Jersey, United States of America). Trimethylolpropane ethoxy triacrylates served as the cross-linker.

In the curing process to obtain the PUA resins, a photoinitiator was used. Such photoinitiator was 1-hydroxy-cyclohexyl-phenyl-ketone or 2-hydroxy-2-methyl-l-phenyl- propanone (2-hydroxy-2-methylpropiophenone) (purchased from Cytec Industries, Inc. of Woodland Park, New Jersey, United States of America) with the structures as follow

The representative structure of the polyurethane acrylate (PUA) repeat unit used in this example is depicted as follow.

The chemical structure of trimethylolpropane ethoxy triacrylates is shown as below.

with x + y + z = sum of x, y and z as defined above. For clarity, for PUA-P9, it refers to a PUA containing urethane acrylate and trimethylolpropane ethoxy triacrylates with x + y + z = 9. Similarly, PUA-P3 and PUA-P20 refer to PUA containing urethane acrylate and trimethylolpropane ethoxy triacrylates with x + y + z = 3 and x + y + z = 20, respectively.

The free volume of the absorptive material plays a critical role in reducing the evaporation rate (ER) of fragrance as described in the present disclosure. Free volume as used herein is defined as the empty space between the polymer linkage chains with another corresponding polymer chain. Such free volume is depicted in Fig. 1A.

b) Solid-state polymeric matrix for the controlled release of fragrance

The resulting porous polymeric matrix obtained upon curing the monomer and the cross linker was then used as the absorptive material to release the fragrance in a controlled manner. The weight of the fragrance-loaded polymeric matrix was measured at regular intervals. The evaporation rate (ER) for the first two hours was calculated based on the gradient of the weight loss vs. time graph. The schematic diagram depicting on how the fragrance release can be slowed is illustrated in Fig. 1A.

bl. PUA-P3, PUA-P9 and PUA-P20 resins as the polymeric matrix

Comparing the evaporation rate (ER, first two hours) across various fragrances as shown in Fig. 2, which were released from the PUA-based resins that serves as the absorptive material, against pure fragrance (in the absence of absorptive material) suggests that PUA- based resins, in particular PUA-P9 resins, can reduce the ER by 2.5- and 8-fold for phenyl ethyl alcohol (PEA) and benzyl acetate (BA), respectively. It is noted that the above performance can be achieved with the thickness of the resin pellets of 0.6 mm.

It can be seen clearly from Fig. 2 that the performance of PUA-P9 resins is better compared to other PUA-based resins counterpart. The ER is normally used as indicator to determine how fast the fragrance vaporizes at room temperature (about 25 °C) and is calculated for the first two hours. It was revealed that PUA-P20 has the highest ER (124 ± 10 mg/m²/min). This suggests that having a pore size such as PUA-P20 is undesirable as the resin does not appear to be able to retain the fragrance for an extended period of time. On the other hand, a lower ER was observed for PUA-P9 (17.0 ± 0.6 mg/m²/min) and PUA-P3 (33 ± 2 mg/m²/min), respectively. The same PUA-based resins were further tested to identify if the resins were able to continue releasing the fragrance after an extended period of time. As can be seen from Figs. 3 A and 3B, it was surprisingly found that the PUA matrix was able to release benzyl acetate (BA) even after three months while the same amount of BA would have completely evaporated after only one week

The long-term performance release profile for BA for various PUA-based resins is depicted in Figs. 3 with PUA-P9 identified as the best performing PUA-based resins. Further, it is shown in Fig. 3B that about 50 wt% of BA remained after 60 days when PUA-P9 resins of 1.0 mm thick were used. This makes it one of the best performing techniques in sustaining the release of top note.

b2. PUA-P9-PETA resins as the polymeric matrix

It was further surprisingly found that the addition of a small molecule (with the chemical structure below) to the formulation in section bl results in a matrix exhibiting better performance than the PUA-P9 resins. The same fragrance, benzyl acetate (BA), was used. The evaporation rate of PUA-P9-PETA-0.3 wt% (PETA is present in the amount of 0.3 wt%) is approximately 2.7-fold lower than that of PUA-P9 resins. This can be seen from Fig. 4.

Interestingly, it is noted from Fig. 4 that the increasing amount of PETA from 0.5 to 1.5 wt% in the PUA resins results in higher evaporation rate. This is probably due to the structure changes (conformational changes) of the free volume space in the matrix. It is also observed from Fig. 4 that the fragrance loading of benzyl acetate (BA) shows similar trend for the same concentration range of PETA.

The above was confirmed by the profile in the weight loss of BA over an extended period of time as can be shown in Fig. 5. It is noted from this figure that PUA-P9-PETA-0.3 wt% shows a slower weight loss compared to PUA-P9 resins over the whole time range tested. However, as shown in Fig. 5, further increasing the PETA’s concentration from 0.5 wt% to 1.5 wt% in the polymeric matrix resulted in faster weight percent loss of BA. A slight decrease in the evaporation rate was observed for the concentration of PETA from 1.5 wt% to 5 wt%. The observations above may be due to a larger free volumetric space in the resins. Still from Fig. 5, it can be observed that the loading of benzyl acetate (BA), expressed in wt%, shows similar trend as the evaporation rate’s profile.

c) Reuse of the PUA-based resins

Further tests on the PUA-based resins described above suggest that the fragrance can be loaded and released from the PUA matrix without damaging the PUA structure. Hence, this confirms that the polymeric material of the present disclosure can be reused for sustainable engineering.

The test involved loading and removal of fragrance performed on the PUA-P9 matrix. Here, the most volatile fragrance, BA was loaded into a PUA-P9 resin of 0.6 mm thick by soaking PUA-P9 resin in BA at about 60°C overnight. BA was released by placing the loaded PUA-P9 resin in a vacuum oven at 80°C for about 5 hours. Fig. 6 indicates the change in weight percent of BA in the resin during the cycling tests (loading and removal). It is estimated that about 14 wt% of BA can be repeatedly loaded into the resin and these fragrances can be removed completely throughout the 10 cycles.

The above suggest that BA does not react or form any physical bonding with PUA-P9. Hence, the structure of PUA-P9 resin can be regarded to remain intact throughout the loading-unloading cycle, suggesting long-term solution to sustainability for industry as an adsorptive material. This is important, in particular in the context of relatively low market price of mass-consumer products, where financial margin is relatively narrow.

In addition to the above appealing properties, the film comprising the PUA-based resins prepared is clear and transparent as can be seen from Fig. 7 to thereby broaden the potential use of such PUA-based resins. Further, the resins can be easily shaped and is amenable for additive manufacturing of 3D printable and / or low viscosity of starting material.

Industrial Applicability

The porous polymeric matrix as defined in the present disclosure may be used in fragrance- controlled devices, whereby the release of fragrance molecules may be prolonged and sustained as desired to create a long lasting performance. The porous polymeric matrix as defined herein may be used for a controlled release of the plurality of fragrance molecules.

The porous polyurethane acrylate (PUA)-based polymeric matrix as defined herein, when used to release the plurality of fragrance molecules, may be able to significantly reduce the evaporation rate of the fragrance molecules. In order to achieve a prolonged and sustained release of the plurality of fragrance molecules, the substituents of polyurethane acrylate (PUA) repeat units as defined herein, the length of the repeat units, and / or the length of the chain of cross-linkers may be adjusted accordingly.

As aforementioned, since the fragrance molecules may form part of the fragrance composition, the porous polymeric matrix may be used in fragrance composition, whereby the fragrance composition may be used in composition that is useful in plant protection, or as an insect repellent. The porous polymeric matrix of the present disclosure can be applied and expanded to other small molecule compounds that require slow and sustained release over time, including but are not limited to insecticides, deodorants, mosquito repellent oil, synthetic biological therapeutic agents and drugs.

The porous polymeric matrix as defined above may be used in filters particularly filters for air-conditioning system. Further, the porous polymeric matrix as defined herein may be used in blowers and fans. Owing to the ability to be reused, the porous polymeric matrix as defined above may be reusable for a range of applications such as used as membrane or a selective layer on a porous support. The porous polymeric matrix as defined herein may be easily shaped and thus, may be suitable to be used for additive manufacturing (or 3D printing).

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

1. A porous polymeric matrix comprising a plurality of cross-linked acrylate monomers, wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm.

2. The porous polymeric matrix according to claim 1, wherein said acrylate monomer is a polyurethane acrylate monomer.

3. The porous polymeric matrix according to claim 2, wherein the polyurethane acrylate monomer has a structure of formula (I):

wherein R R₂, R and R are each independently selected from an optionally substituted C oalkyl and a moiety of formula (II),

wherein

R is absent or optionally substituted Ci_ alkanediyl;

o is an integer selected from 0, 1, 2, and 3;

R₆, R₇, R₈, R₉ are each independently selected from the group consisting

wherein R_a is optionally substituted C_{1 5}alkyl;

n is an integer selected from 0, 1, 2, 3 and 4;

p is an integer selected from 0, 1, 2 and 3; and

m is an integer selected from 0, 1, 2, 3, 4, 5 and 6;

with the proviso that at least one of the R_l R₂, R₃ or R₄ is the moiety of formula (II), wherein ( ^JWI/' ) indicates the point of attachment of R₆, R₇, R_s and R₉ in the moiety of formula (II).

4. The porous polymeric matrix according to any one of claims 1 to 3, wherein said acrylate monomer is cross-linked by a cross-linker, wherein said cross-linker is an acrylate- based cross-linker.

5. The porous polymeric matrix according to claim 4, wherein said acrylate-based cross-linker has a structure of formula (III)

wherein:

R is optionally substituted Ci ^alkyl; and

6. The porous polymeric matrix according to claim 5, wherein said acrylate-based cross-linker of formula (III) is

wherein x, y and z are each independently an integer selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

7. The porous polymeric matrix according to any one of claims 2 to 6, wherein said polymeric matrix further comprises a second polyurethane acrylate monomer.

8. The porous polymeric matrix according to claim 7, wherein said second polyurethane acrylate monomer has the same structure as the polyurethane acrylate monomer defined in claim 3.

9. The porous polymeric matrix according to claim 7, wherein said second polyurethane acrylate monomer has a different structure as the polyurethane acrylate monomer defined in claim 3.

10. The porous polymeric matrix according to claim 7 or 9, wherein said second polyurethane acrylate monomer has the following structure

11. The porous polymeric matrix according to any one of claims 7 to 10, wherein the amount of said second polyurethane acrylate monomers is less than 30 wt% based on the total weight of said polymeric matrix.

12. The porous polymeric matrix according to any one of claims 7 to 11, wherein the amount of said second polyurethane acrylate monomers is less than 1 wt% based on the total weight of said polymeric matrix.

13. The porous polymeric matrix according to any one of claims 2 to 12, wherein said polyurethane acrylate monomers and/ or the plurality of acrylate-based cross-linkers are curable.

14. The porous polymeric matrix according to any one of claims 1 to 13, wherein said porous polymeric matrix is a solid-state polymer.

15. The porous polymeric matrix according to any one of claims 1 to 14, wherein said porous polymeric matrix has a pore diameter in the range between 5 nm to 25 nm.

16. Use of a porous polymeric matrix for a controlled release of the plurality of fragrance molecules, wherein the porous polymeric matrix comprises a plurality of cross- linked acrylate monomers, and wherein the pores of the porous polymeric matrix have a pore diameter of less than 30 nm.

17. The use according to claim 16, wherein said porous polymeric matrix comprises a polyurethane acrylate monomer of the following structure:

18. The use according to claim 16 or 17, wherein said porous polymeric matrix further comprises a second polyurethane acrylate monomer of the following structure:

19. The use according to any one of clai 16 to 18, wherein said fragrance molecules form part of a fragrance composition, wherein the fragrance composition comprises an aromatic compound or a mixture of aromatic compounds having a molecular weight of less than 300 Da.

20. A method for releasing a plurality of the fragrance molecules, comprising the steps of:

21. The method according to claim 20, wherein said porous polymeric matrix provided in step i) is as defined in any one of claims 1 to 15.

22. The method according to claim 20 or 21, wherein said fragrance molecules present in step ii) form part of a fragrance composition, wherein the fragrance composition comprises an aromatic compound or a mixture of aromatic compounds having a molecular weight of less than 300 Da.