High purity polysiloxane macromer and method for producing same

Abstract

A method for synthesizing high purity acryloxyalkyldimethylchlorosilanes includes the steps of (a) reacting an acrylate with a haloalkyldimethylalkoxysilane to form an acryloxy-substituted alkyldimethylalkoxysilane, and (b) replacing the alkoxy group in the acryloxy-substituted alkyldimethylalkoxysilane with a chloride-containing compound to form an acryloxyalkyldimethylchlorosilane. The acryloxyalkyldimethylchlorosilanes can be used as end-capping agents in AROP and have a purity of greater than about 99% and contain no detectable isomers or hydrogenation impurities.

Description

[Technical field]

[0001] Acrylate-functional polysiloxane macromers continue to find applications where precise control of mechanical, optical, or electrical properties is essential in the end use. The most common siloxane macromer, monomethacryloxypropyl-terminated polydimethylsiloxane, most commonly referred to as MPDMS or MCR-M11, has the formula (1):

[0002] [ka] [Background technology]

[0003] Impurities found in acrylate-functional polysiloxane macromers often have deleterious effects on end-use applications. For example, similar problems occur in variations of the most commonly used macromers, including those containing backbones with trifluoropropyl substitution and those with symmetrical structures, such as those having formulas (2) and (3).

[0004] [ka]

[0005] For example, isomeric impurities can lead to non-uniformity in the structure of the copolymer, and inert impurities can lead to extractable species that can affect biocompatibility or result in domain separation that affects the optical properties of the copolymer.

[0006] Polysiloxane macromers are formed by living anionic ring-opening polymerization (AROP). This chemistry has been described by Goff et al. (see "Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization", Molecules, 26, 2755 (2021)). Conditions that avoid redistribution reactions during the polymerization to form the siloxane-containing macromers are crucial to achieving purity, but most of those variables are now understood. The most significant limitation in achieving high purity is the "end-capping" or "terminating" reagent utilized in the AROP reaction, 3-(methacryloxy)propyldimethylchlorosilane, having the formula (4).

[0007] [ka]

[0008] This endcapping material is traditionally produced by hydrosilylation of allyl methacrylate. The earliest definitive synthesis of this product was reported by Cameron (Polymer, 26, 437 (1985)) in a 50% yield with an unspecified final purity. Unfortunately, the reaction is not clean and the reaction mixture is not easily purified due to the close boiling points of the products as well as their tendency to polymerize during the process. The major by-product is the β-isomer, 1-methyl-2-methacryloxyethyldimethylchlorosilane (Formula (5)).

[0009] [ka]

[0010] Other by-products include the desired 3-(methacryloxy)propyldimethylchlorosilane and the hydrogenated analog of the β-isomer. The hydrogenated analog of the desired product, isobutyloxypropyldimethylchlorosilane, has the formula (6).

[0011] [ka]

[0012] The origin of these impurities is the selectivity of the hydrosilylation catalyst, which favors the anti-Markovnikov addition products while also allowing the formation of normal Markovnikov products, allowing minor dehydrocoupling reactions, and catalyzing the hydrogenation of acrylate double bonds. Hydrosilylation occurs, but is not limited to, with the preference for allylic groups, and to a lesser extent with acrylate unsaturation. Although there is allylic unsaturation in the product formed by hydrosilylation of acrylate double bonds, it is essentially unreactive with the outcome under normal polymerization conditions, and macromers derived from this by-product are still extractable. For example, unlike methacrylate-functional macromers, allyl-functional macromers do not readily undergo photopolymerization.

[0013] [ka]

[0014] In addition, the primary by-product formed from the removal of propylene is methacryloxydimethylchlorosilane (formula (8)), which can undergo exchange reactions with silicon-bonded chlorine to produce compounds having formula (9).

[0015] [ka]

[0016] This description of impurities is not meant to be exhaustive, but rather to illustrate many of the problems involved and the difficulties in producing high purity macromers from acryloxy-functional endcapping agents produced by hydrosilylation.

[0017] Aside from the obvious structural impurities that arise from incorporating structural analogs of the endcapping agent into the desired macromer, difficulties arise in determining the exact amount of endcapping agent required to achieve molecular weight control. Obtaining high yields and purity of the endcapping agent is extremely important for both economics and performance.

[0018] A method to obtain a higher yield of 3-(methacryloxy)propyldimethylchlorosilane has been reported by Cracknell (WO2016 / 005757), where by-products were minimized by process control utilizing the same basic chemistry. However, the reported purity of the isolated product was only 89%, with no acknowledgement or reporting of isomers or hydrogenation by-products. A more detailed synthesis is reported in U.S. Patent No. 5,847,178 to Ohkawa and U.S. Patent No. 5,811,565 to Mikami, where it was demonstrated that purity as high as 98.8% could be achieved by decomposing the β-isomer in a post-synthetic step by the addition of a copper reagent. More recently, JP2003-096086 to Nishiwaki describes the use of an iridium catalyst, also resulting in a purity of 98.8%. It should be noted that only one of the previously reported syntheses (U.S. Patent No. 5,493,039 to Ohkawa) mentioned reduced amounts of a reduced analog of the target compound, isobutyloxypropyldimethylchlorosilane (also known as α-methylpropionyloxypropyldimethylchlorosilane), either as a baseline or as an improvement, presumably because this product identification was not possible using older gas chromatography techniques. Furthermore, all of the previous literature reports of high purity appear to be overestimates, since at least at the time of these references, analytical limitations typically lacked the sensitivity to determine hydrogenation and isomeric by-products, making failure to meet performance criteria seem unexplained.

[0019] Reduced by-products are particularly problematic because they introduce non-polymerizable, extractable impurities into those produced from nominally pure methacrylate-functional polysiloxane macromers. To date, there is no method to produce meth(acryloxy)alkyldimethylchlorosilanes that contain no isomers or hydrogenation by-products via hydrosilylation or any other reaction route, making them suitable for critical applications. For example, in optical applications such as contact lenses, this class of impurity can result in reduced transparency and eye irritation due to unreacted polymeric species acting as contaminants in otherwise fully polymerizable macromers and migrating, phase-separating, or extracting. It is therefore highly desirable to be able to produce acryloxyalkyldimethylchlorosilanes in high yields and without detectable isomers or hydrogenation by-products. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] WO2016 / 005757 issue [Patent Document 2] U.S. Patent No. 5,847,178 [Patent Document 3] U.S. Patent No. 5,811,565 [Patent Document 4] JP2003-096086 issue [Non-patent literature]

[0021] [Non-Patent Document 1] Goff et al., “Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization,” Molecules, 26, 2755 (2021) [Non-Patent Document 2] Cameron, Polymer, 26, 437 (1985) [Non-Patent Document 3] T. Sengupta et al., Journal of the Indian Chemical Society, 53:7, 726–7 (1976) Summary of the Invention [Means for solving the problem]

[0022] In one aspect of the present disclosure, an acryloxyalkyldimethylchlorosilane is provided having a purity of at least about 99% and containing less than about 0.1% by weight of hydrogenation by-products and less than about 0.1% by weight of isomeric by-products.

[0023] In another aspect of the disclosure, (a) reacting an acrylate with a haloalkyldimethylalkoxysilane to form an acryloxy-substituted alkyldimethylalkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyldimethylalkoxysilane using a chlorine-containing compound to form an acryloxyalkyldimethylchlorosilane; The present invention provides a method for synthesizing high purity acryloxyalkyldimethylchlorosilane, comprising:

[0024] In a further aspect of the present disclosure, there is provided a methacrylate-functional macromer or copolymer derived from an acryloxyalkyldimethylchlorosilane having a purity of at least about 99%.

[0025] The advantageous improvements of the present invention, which may be implemented alone or in combination, are set out in the appended claims.

[0026] In summary, the following embodiments are presented as particularly preferred within the scope of the present invention.

[0027] Embodiment 1: An acryloxyalkyldimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1% by weight of hydrogenation by-products and less than about 0.1% by weight of isomeric by-products.

[0028] Embodiment 2: The acryloxyalkyldimethylchlorosilane of embodiment 1, containing less than about 0.05% by weight hydrogenation by-products and less than about 0.05% by weight isomeric by-products.

[0029] Embodiment 3: The acryloxyalkyldimethylchlorosilane of embodiment 1 or 2, which is a (meth)acryloxyalkyldimethylchlorosilane.

[0030] Embodiment 4: The acryloxyalkyldimethylchlorosilane of embodiment 3, containing less than about 0.05% by weight isobutyloxypropyldimethylchlorosilane and less than about 0.05% by weight 1-methyl-2-methacryloxyethyldimethylchlorosilane.

[0031] Embodiment 5: The acryloxyalkyldimethylchlorosilane of any one of embodiments 1 to 4, having a purity of greater than about 99.3%.

[0032] Embodiment 6: The acryloxyalkyldimethylchlorosilane of any one of embodiments 1 to 5, which is 3-methacryloxypropyldimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, or 3-(methacryloxy)propylmethyldichlorosilane.

[0033] Embodiment 7: (a) reacting an acrylate with a haloalkyldimethylalkoxysilane to form an acryloxy-substituted alkyldimethylalkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyldimethylalkoxysilane using a chlorine-containing compound to form an acryloxyalkyldimethylchlorosilane; 1. A method for synthesizing high purity acryloxyalkyldimethylchlorosilane, comprising:

[0034] Embodiment 8: The method of embodiment 7, wherein step (a) is a phase transfer catalysis reaction.

[0035] Embodiment 9: The method of embodiment 7 or 8, wherein step (a) comprises the steps of (i) reacting a halogen salt with methacrylic acid to form an acrylate salt, and (ii) reacting the acrylate salt with a haloalkyldimethylalkoxysilane.

[0036] Embodiment 10: The method of any one of embodiments 7 to 9, wherein step (b) is an exchange or substitution reaction.

[0037] Embodiment 11: The method of any of embodiments 7 to 10, wherein step (b) comprises reacting an acryloxy-substituted alkyldimethylalkoxysilane with acetyl chloride and a weak Lewis acid catalyst.

[0038] Embodiment 12: The method of any of embodiments 7 to 11, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and the product of step (a) is a (meth)acryloxyalkyldimethylalkoxysilane.

[0039] Embodiment 13: The method of any of embodiments 7 to 12, wherein the acryloxyalkyldimethylchlorosilane is 3-methylacryloxypropyldimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, or 3-(methacryloxy)propylmethyldichlorosilane.

[0040] Embodiment 14: The method of any of embodiments 7 to 13, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99%.

[0041] Embodiment 15: The method of any one of embodiments 7 to 14, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99.3%.

[0042] Embodiment 16: The method of any of embodiments 7 to 15, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.1% by weight of hydrogenation by-products and less than about 0.1% by weight of isomeric by-products.

[0043] Embodiment 17: The method of any of embodiments 7 to 16, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.05% by weight of hydrogenation by-products and less than about 0.05% of isomeric by-products.

[0044] Embodiment 18: The method of any one of embodiments 7 to 17, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and contains less than about 0.05% by weight of isobutyloxypropyldimethylchlorosilane and less than about 0.05% by weight of 1-methyl-2-methacryloxyethyldimethylchlorosilane.

[0045] Embodiment 19: A method for synthesizing a high purity (meth)acryloxyalkyldimethyl-functional polysiloxane macromer, comprising carrying out a living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as a starting material and an acryloxyalkyldimethylchlorosilane as described in any one of embodiments 1 to 6 as a terminating reagent.

[0046] Embodiment 20: The method of embodiment 19, wherein the polysiloxane is monomethacryloxypropyl-terminated polydimethylsiloxane.

[0047] Embodiment 21: The method of embodiment 19 or 20, wherein the polysiloxane is substantially free of non-polymeric polysiloxanes.

[0048] Embodiment 22: The method of any one of embodiments 19 to 21, wherein the polysiloxane contains less than about 0.1% by weight of impurities containing hydrogenated derivatives or isomers of (meth)acryloxyalkyl functional groups.

[0049] Embodiment 23: A methacrylate-functional macromer or copolymer derived from an acryloxyalkyldimethylchlorosilane having a purity of at least about 99%.

[0050] Embodiment 24: A macromer or copolymer according to embodiment 23, containing less than about 0.1% by weight of a hydrogenated derivative of the methacrylate functional group.

[0051] Embodiment 25: A macromer or copolymer according to embodiment 23 or 24, containing less than about 0.05% by weight of a hydrogenated derivative of the methacrylate functional group.

[0052] Embodiment 26: The macromer or copolymer of any of embodiments 23 to 25, having a molecular weight of less than about 5,000 Daltons.

[0053] Embodiment 27: A methacrylate-functional macromer or copolymer having a purity of at least about 99.3% and derived from an acryloxyalkyldimethylchlorosilane as defined in any of embodiments 23 to 26. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The present disclosure relates to a method for synthesizing high purity acryloxyalkyldimethylchlorosilanes, which are suitable endcapping agents for living AROP. These high purity compounds allow for the preparation of high purity acryloxyalkyl terminated poly(siloxanes) that are substantially free of isomers and hydrogenation by-products and substantially free of non-polymerizable polysiloxanes. The disclosed method avoids hydrosilylation of acrylates and instead utilizes a substitution reaction that does not involve isomerization or reduction chemical mechanisms. In a preferred embodiment, the endcapping agent produced by the present method is 3-methacryloxypropyldimethylchlorosilane (formula (4)) with a purity of about 99% or greater and no detectable hydrogenated analog (isobutyloxypropyldimethylchlorosilane, having formula (6)) or β-isomer (1-methyl-2-methacryloxyethyldimethylchlorosilane, having formula (5)). This high purity compound can be used as an endcapping agent or terminating agent for the production of monomethacryloxypropyl terminated polydimethylsiloxanes. Other examples of high purity compounds suitable as endcapping or terminating reagents for the living AROP synthesis of macromers that can be synthesized by the methods described herein include (methacryloxymethyl)dimethylchlorosilane and 3-(acryloxymethyl)dimethylchlorosilane, which have not previously been synthesized.

[0055] In all cases, the compounds described herein are substantially free of isomers and hydrogenation by-products / reducible analogs. The negative impact of impure end-capping compounds is most pronounced when the macromers are relatively low molecular weight, especially below about 5,000 Daltons. At higher molecular weights, the non-reactive macromers formed from the reducible analogs can be solubilized in the final polymer, where the macromers form pendant groups in the copolymer. Copolymers derived from low molecular weight macromers can experience loss of optical transparency caused by phase separation of the reducible analogs. The materials and methods described herein solve the problem of optical defects associated with low molecular weight macromers incorporated as comonomers in polymers utilized in forming contact lenses.

[0056] For the purposes of this disclosure, the term "high purity" can be understood to mean a purity of greater than about 99%, more preferably greater than about 99.2%, and even more preferably greater than about 99.3%. The term "substantially free" can be understood to mean that impurities are not detected by GC and GC-MS, which typically have a detection limit of less than about 0.05% by weight. Thus, the present method provides for the synthesis of acryloxyalkyldimethylchlorosilanes that have high purity and also have no detectable isomers or hydrogenation by-products, i.e., less than about 0.1% by weight, or less than about 0.05% by weight of isomers or hydrogenation by-products. Other impurities that may be present have little effect on the AROP or on the performance of the resulting macromer.

[0057] The method for synthesizing high purity acryloxyalkyldimethylchlorosilanes includes (a) forming an acryloxy-substituted alkyldimethylalkoxysilane, preferably by phase transfer catalysis between an acrylate and a (haloalkyl)dimethylalkoxysilane, and then (b) replacing the alkoxy group with a halide, preferably by exchange or substitution reaction. In step (a), the preferred acrylate is potassium methacrylate, which can be generated in-situ, for example, from the reaction of potassium carbonate with methacrylic acid. The preferred (haloalkyl)dimethylalkoxysilane is 3-chloropropyldimethylethoxysilane. Alternatively, but less preferably, acrylic acid may be reacted with a haloalkylsilane in the presence of a base acceptor. However, this chemistry cannot directly produce the preferred methacryloxypropyldimethylchlorosilane, since the acrylate also reacts with silicon-bonded chlorine. Thus, it has been found that producing methacryloxypropyldimethylalkoxysilanes is an intermediate in nature. In a preferred embodiment, the high purity endcapping agent is (meth)acryloxypropyldimethylchlorosilane and the intermediate is (meth)acryloxypropyldimethylethoxysilane.

[0058] There are many known synthetic methods available for converting the silicon-bonded alkoxy groups to halides in the second reaction step (b). For example, ethoxy groups on silicon can be exchanged for chlorine by reaction with thionyl chloride, phosphoryl trichloride, phosphorus pentachloride, benzyl chloride, boron trichloride, tin tetrachloride, methyltrichlorosilane, or acid chlorides, among others. The most commonly used reagents, thionyl chloride and phosphorus pentachloride, can additionally cleave acrylic esters to form acid chlorides, all of which 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. However, strong Lewis acids have the potential to catalyze reactions involving acrylate functional groups. Currently, the preferred reactant pair for the exchange reaction is acetyl chloride and a weak Lewis acid catalyst, preferably ferric chloride, which does not cleave the acrylate ester or cause polymerization.

[0059] The synthetic methods described above are generally applicable to produce analogs and congeners of 3-methacryloxypropyldimethylchlorosilane, with purities greater than about 99%, more preferably greater than about 99.2%, and even more preferably greater than about 99.3%, without detectable isomer contamination or hydrogenation by-product contamination, and are suitable for use in the synthesis of high purity acrylate-functional macromers. Other examples of compounds of similar functional structure that can be produced in high purity by the methods described herein and free of detectable isomers and hydrogenation by-products include methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, and 3-(methacryloxy)propylmethyldichlorosilane. Meanwhile, similar bromosilanes can be prepared by similar methods, but these are less practical, mainly due to economics.

[0060] Another indirect indication of the purity of the endcapping agent produced in this manner is the observation that less excess of the theoretical stoichiometric amount of endcapping agent is required to terminate a living AROP polymerization: for example, 2% excess of the theoretical amount of endcapping agent is required when the endcapping agent is traditionally produced by hydrosilylation, whereas only 1% excess of the theoretical amount of the high purity endcapping agent described herein is required to terminate a polymerization.

[0061] Aspects of the present 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 lithium dimethylsilanolate, which is formed by the reaction of an alkyllithium reagent with a strained cyclic siloxane, most commonly hexamethylcyclotrisiloxane. The lithium silanolate can be isolated or formed in situ. Ring-opening polymerization proceeds with additional strained cyclic siloxanes in the presence of a strained ring with a promoter, typically an aprotic polar material such as dimethylformamide or tetrahydrofuran. Finally, end-capping of the polymer with a chlorosilane, such as 3-(methacryloxy)propyldimethylchlorosilane, most commonly used, completes the formation of the macromer. Symmetric macromers are formed similarly, but the dichlorosilane couples rather than terminating the reaction. These macromers and copolymers have a purity of greater than about 99%, more preferably greater than about 99.2%, and even more preferably greater than about 99.3%, contain less than about 0.1% by weight hydrogenation impurities and less than about 0.1% by weight isomeric impurities, and have a molecular weight of less than about 5,000 daltons, more preferably less than about 1,000 daltons.

[0062] A further aspect of the present disclosure relates to methods for producing high purity (meth)acrylate functional macromers derived from high purity endcapping agents, including previously unprepared meth(acryloxy)methyl terminated macromers. Specifically, these macromers can be produced using AROP procedures well known in the art and utilizing the high purity endcapping agents described herein.

[0063] For example, a method for synthesizing a high purity (meth)acryloxyalkyldimethyl functional asymmetric polysiloxane macromer includes carrying out a living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as the starting material and the previously described acryloxyalkyldimethylchlorosilane as the end-capping agent. In a preferred embodiment, the polysiloxane is a monomethacryloxypropyl terminated polydimethylsiloxane. The resulting polysiloxane is substantially free of non-polymeric polysiloxanes and contains less than about 0.1% by weight (or less than 0.05% by weight in a preferred embodiment) of impurities containing hydrogenated derivatives or isomers of the (meth)acryloxyalkyl functional group. Similarly, a symmetric polysiloxane macromer can be derived from 3-(methacryloxypropyl)methyldichlorosilane.

[0064] The invention will now be described with reference to the following non-limiting examples. EXAMPLES

[0065] (Comparison): Synthesis of methacryloxypropyldimethylchlorosilane Allyl methacrylate (1261 g, 10.0 mol) and BHT (4 wt%, 83.9 g) were charged to the reactor and O2 / Ar sparging was started. The reaction mixture was heated to 75°C and then Karstedt's catalyst (2% Pt in xylene, 1 ml) was added. Dimethylchlorosilane (969.8 g, 10.3 mol) was added dropwise over 6 hours while maintaining the vessel temperature between 65-85°C. The resulting reaction mixture was stirred at 80°C for 1 hour. Phenothiazine (5 wt%) was added to the reaction mixture and purified using a wiped film evaporator to give a clear, colorless liquid (1100 g, 50%). Analytical data: 1 H NMR (400 MHz, CDCl3) δ 6.10 (s, 1H), 5.56 (s, 1H), 4.15-4.12 (t, J = 7.2 Hz, 2H), 1.94 (s, 3H), 1.78 (m, 2H), 0.88 (m, 2H), 0.43 (s, 3H); 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%, β-isomer - 2.01%, Isobutyloxypropyldimethylchlorosilane - 0.88%; GC-MS m / z: 220 (M), 205 (M - Me). To remove disiloxane, an artifact formed during sample handling, the hydrolysis (disiloxane) product formed during analysis was added back in, and the purity of the product was 89.7%. EXAMPLES

[0066] Synthesis of 3-methacryloxypropyldimethylethoxysilane

[0067] [ka]

[0068] A 2 L, 4-neck flask was equipped with a mechanical stirrer, heating mantle, addition funnel, vessel temperature probe, fritted glass dispersion tube, and Dean-Stark trap with water condenser. Di-t-butylhydroxytoluene (BHT) (4.19 g, 3.50 wt%) and toluene (960 g) were charged to the reactor. Stirring was started and potassium carbonate (109.1 g, 7.67 mol) was added. The slurry was heated to 80° C. with O2 / Ar sparging, then methacrylic acid (119.9 g, 1.40 mol) was added dropwise at 100° C. over 2 h. Carbon dioxide gas evolution was observed and water was removed via the Dean-Stark trap under reflux conditions. An azeotrope was observed from 90° C. After removing all the by-product water, tetrabutylphosphonium chloride (50% in toluene) (29.5 g, 0.031 mol) and 3-chloropropyldimethylethoxysilane (240.0 g, 1.33 mol) were added to the flask. The reaction mixture was heated at reflux for 3 hours and then cooled to room temperature. The reaction mixture was filtered. The filtrate was concentrated in vacuo and 5% by weight of phenothiazine was added. The product was then purified on a wiped film evaporator at 0.6-0.7 mmHg vacuum, jacket temperature of 64-5°C and cold finger temperature of 30°C to give the final product 3-methacryloxypropyldimethylethoxysilane as a clear, colorless liquid (202.6 g, 66.2%) with a product:residue separation ratio of 4:1. Analytical Data: 1 H NMR (400 MHz, CDCl3) δ 6.08 (s, 1H), 5.55 (s, 1H), 4.07-4.10 (t, J = 7.2 Hz, 2H), 3.61-3.66 (q, J = 13.6 Hz, 2H), 1.91 (s, 3H), 1.63-1.73 (m, 2H), 1.12-1.20 (t, J = 6.8 Hz, 3H), 0.6 (m, 2H), 0.09 (S, 6H); FTIR (cm -1): 2956.15, 2927.88, 2893.38, 1718.05, 1638.46, 1451.95, 1389.58, 1320.36, 1294.94, 1250.75, 1158.40, 1105.72, 1077.42, 937.89, 836.16; GC-TCD: purity - 99.3%; GC-MS m / z: 229.2 (M), 215.1 (M - Me), 184.1 (M - OEt). The levels of β-isomer and isobutyloxypropyldimethylethoxysilane were both below the detection level by capillary GC and GC-MS, i.e. less than 0.05%. EXAMPLES

[0069] Synthesis of 3-methacryloxypropyldimethylchlorosilane

[0070] [ka]

[0071] A 1 L, 4-neck reactor was equipped with a magnetic stirrer, vessel temperature probe, cooling bath, addition funnel, packed column, and distillation head containing 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-Methacryloxypropyldimethylethoxysilane prepared in Example 2 and inhibited with 1 wt% BHT (345.5 g, 1.50 mol) and phenothiazine (1.50 g, 0.01 mol) was added dropwise to the reaction mixture at such a rate as to maintain the reaction temperature at 20-25°C. An exothermic reaction was observed and the mixture changed color from yellow to brown. (When the reaction was carried out without the use of a cooling bath, a temperature increase of 30-40°C was observed.) The resulting reaction mixture was stirred at room temperature for 12 hours. The mixture was concentrated in vacuo at 5 mmHg at a maximum temperature of 80°C and purified by wiped film evaporator (5% by weight phenothiazine, 45-48°C, 0.5 mmHg, cold finger 25°C, separation ratio 3:1) to give the product as a clear, colorless liquid (270.4 g, 81.7%). GC-TCD: purity 98.91%. To remove the disiloxane, an artifact formed during sample handling, the hydrolysis (disiloxane) product formed during analysis was added back, and the product purity was 99.3%. BHT (4% by weight) was added to the final product as an inhibitor. Analytical data: 1 H NMR (400 MHz, CDCl3) δ 6.10 (s, 1H), 5.56 (s, 1H), 4.15-4.12 (t, J = 7.2 Hz, 2H), 1.94 (s, 3H), 1.78 (m, 2H), 0.88 (m, 2H), 0.43 (s, 3H); 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-MS m / z: 220 (M), 205 (M - Me). Isobutyloxypropyldimethylchlorosilane and 1-methyl-2-methacryloxyethyldimethylchlorosilane were not observed down to the detection limit of 0.05%. EXAMPLES

[0072] Synthesis of (methacryloxymethyl)dimethylethoxysilane A 22 L, 4-neck flask was equipped with a mechanical stirrer, heating mantle, addition funnel, vessel temperature probe, fritted glass dispersion tube, and a distillation head mounted on a 500 cm packed column. The flask was charged with 3000 mL of cyclohexane and 3718 g of a 32% solution of potassium methoxide in methanol. Stirring and subsurface air sparging of the liquid were started. Methacrylic acid (1439 mL, inhibited with BHT) was added through the addition funnel while maintaining the temperature below 60° C. After the addition was complete, the pH was >9. The flask was then heated to remove the methanol. When the vessel temperature reached 71-73° C., the methanol was removed from the vessel and the cyclohexane in the Dean-Stark trap was clear. Approximately 100 mL of clear cyclohexane was not returned to the vessel. After all the methanol was removed and the flask was cooled to room temperature, chloromethyldimethylethoxysilane (2119 ml) was added to the flask via the addition funnel, followed by 69.7 g of tetrabutylammonium bromide. The flask was heated to 80-90°C for 20 hours, at which time all the raw materials had reacted. After the reaction was complete, the mixture was filtered, the salts were rinsed with two 1 L portions of cyclohexane, and the filtrate was concentrated. 1 g of the methyl ether of hydroquinone (MEHQ) and 1 g of phenothiazine were added and concentrated. The product was distilled through a 0.25 m packed column at 62-4°C under 0.3 mm Hg vacuum. For storage, it was inhibited with 20 ppm MEHQ and stored at <5°C. EXAMPLES

[0073] Synthesis of (methacryloxymethyl)dimethylchlorosilane

[0074] [ka]

[0075] (Methacryloxymethyl)dimethylchlorosilane was prepared from the product of Example 4 under conditions similar to those of Example 3. A 500 mL 4-neck flask was equipped with a magnetic stirrer, a vessel temperature probe, a cooling bath, an addition funnel, a packed column, and a distillation head protected with N2. Ferric chloride (0.57 g, 0.003 mol) and acetyl chloride (40.6 g, 0.52 mol) were charged to the reactor. A premix of 3-methacryloxymethyldimethylethoxysilane (101 g, 0.50 mol) and phenothiazine (0.5 g, 0.5 wt %) was added dropwise to the reaction mixture at such a rate as to maintain the reaction temperature between 20-25°C. An exothermic reaction was observed and the color of the mixture changed from yellow to brown. The resulting reaction mixture was stirred at room temperature for 12 h. The mixture was concentrated by sparging with O2 / Ar in vacuo, and 0.5 wt % phenothiazine was added. The product was purified by distillation at 3-4 mmHg and 57-59°C to give the final product, 3-methacryloxymethyldimethylchlorosilane, as a clear, colorless liquid (22.0 g, 22.8%). Analytical Data: 1 FTIR (cm -1 ): 2963.01, 1698.46, 1635.40, 1452.12, 1400.94, 1379.80, 1331.06, 1306.77, 1255.92, 1164.14, 1107.79, 1007.47, 945.94, 867.54, 821.31, 760.86, 680.83, 650.27, 596.07, 473.47; GC-TCD: Purity - 99.2%; GC-MS m / z: 192 (M), 177 (M - Me), 157 (M - The level of Cl).isobutyloxymethyldimethylchlorosilane was below the detection level by GC and GC-MS using a capillary column, i.e., less than 0.1%. EXAMPLES

[0076] Synthesis of monobutyl- and monomethacryloxypropyl-terminated polydimethylsiloxane Hexamethylcyclotrisiloxane (D3, 204.2 g, 0.92 mol) and hexane (134.5 g, 2.62 mol) were added to a 1 L round bottom flask containing a magnetic stir bar. The flask was sparged with nitrogen and the reaction mixture was stirred at room temperature for 2 h. n-Butyl lithium (2.6 M in hexane, 69.3 g, 0.26 mol) was added to the reaction flask through an addition funnel and the solution was stirred for 1 h, followed by the addition of dimethylformamide (DMF, 18.2 g, 0.25 mol) to the solution as a polymerization accelerator. After stirring for 3 h, the polymer was terminated with 3-methacryloxypropyldimethylchlorosilane (prepared in Example 3) to give monobutyl-, monomethacryloxypropyl-terminated polydimethylsiloxane. The solution was then stirred overnight and washed with 178 g of deionized water. The aqueous and organic layers were separated and the organic layer was dried over sodium sulfate, filtered and stripped by sparging with dry air under vacuum at 95°C. EXAMPLES

[0077] Comparison of comparative products and inventive products The 3-methacryloxypropyldimethylchlorosilane derived macromer produced by hydrosilylation (Comparative, Example 1) and the high purity material of the present invention prepared in Example 3 were analyzed and compared in the table below.

[0078] [Table 1]

[0079] Comparative Example 8: Example 1 of U.S. Patent No. 5,493,039 to Okawa Using the same conditions and scale, 3-methacryloxypropyldimethylchlorosilane was synthesized as described in Example 1 of U.S. Patent No. 5,493,039 to Ohkawa, except that the water content of the allyl methacrylate was 37 ppm instead of 171 ppm. Analysis of the product revealed the presence of isobutyloxypropyldimethylchlorosilane (0.59%) and the β-isomer (1.47%). The purpose of this comparative example was to demonstrate that reduction products were in fact produced during the hydrosilylation process, although not reported by Ohkawa. The level of isobutyloxymethyldimethylchlorosilane was below the detection level by GC and GC-MS using a capillary column, i.e., less than 0.05%.

[0080] Comparative Example 9: Practical Example 1 of Mikami's U.S. Patent No. 5,811,565 3-Methacryloxypropyldimethylchlorosilane was synthesized as described in Practical Example 1 of Mikami's U.S. Pat. No. 5,811,565, except that phenothiazine was replaced with 3,5-di-t-butyl-4-hydroxyphenylmethyldimethylammonium chloride as the inhibitor and the reaction mixture was sparged with O2 / Ar during the hydrosilylation. Analytical data before the addition of the copper reagent showed the presence of both isobutyloxypropyldimethylchlorosilane (0.26%) and the β-isomer (1.87%). After the addition of copper(II) chloride, the content of the β-isomer was observed to be reduced to less than 1.0%, while no change was observed in the isobutyloxypropyldimethylchlorosilane content. The purpose of this comparative example was to demonstrate that, although not reported by Mikami, reduction products were in fact produced during this hydrosilylation process. The level of isobutyloxymethyldimethylchlorosilane was below the detection level by GC and GC-MS using a capillary column, i.e., less than 0.05%.

[0081] It can be clearly observed that the 3-methacryloxypropyldimethylchlorosilane prepared by the method of the present disclosure not only has a dramatically higher purity than the same material prepared by conventional hydrosilylation, but also has no detectable β-isomer or hydrogenation by-products. Moreover, the excess percentage required when using this compound as an end-capping agent for AROP is reduced by half.

[0082] It will be appreciated by those skilled in the art that changes to the embodiments described above may be made without departing from the broad inventive concept thereof. It is understood, therefore, that the invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as defined by the appended claims.

Claims

1. 1. An acryloxyalkyldimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1% by weight of hydrogenation by-products and less than about 0.1% by weight of isomeric by-products.

2. 10. The acryloxyalkyldimethylchlorosilane of claim 1 containing less than about 0.05% by weight hydrogenation by-products and less than about 0.05% by weight isomeric by-products.

3. 3. The acryloxyalkyldimethylchlorosilane according to claim 1, which is a (meth)acryloxyalkyldimethylchlorosilane.

4. 4. The acryloxyalkyldimethylchlorosilane of claim 3, containing less than about 0.05% by weight isobutyloxypropyldimethylchlorosilane and less than about 0.05% by weight 1-methyl-2-methacryloxyethyldimethylchlorosilane.

5. 5. The acryloxyalkyldimethylchlorosilane of any one of claims 1 to 4, having a purity of greater than about 99.3%.

6. 6. The acryloxyalkyldimethylchlorosilane according to any one of claims 1 to 5, which is 3-methacryloxypropyldimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, or 3-(methacryloxy)propylmethyldichlorosilane.

7. (a) reacting an acrylate with a haloalkyldimethylalkoxysilane to form an acryloxy-substituted alkyldimethylalkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyldimethylalkoxysilane using a chlorine-containing compound to form an acryloxyalkyldimethylchlorosilane; 1. A method for synthesizing high purity acryloxyalkyldimethylchlorosilane, comprising:

8. 8. The method of claim 7, wherein step (a) is a phase transfer catalysis reaction.

9. 9. The method of claim 7 or 8, wherein step (a) comprises the steps of: (i) reacting a halogen salt with methacrylic acid to form an acrylate salt; and (ii) reacting the acrylate salt with a haloalkyldimethylalkoxysilane.

10. 10. The method according to any one of claims 7 to 9, wherein step (b) is an exchange or substitution reaction.

11. 11. The method of any one of claims 7 to 10, wherein step (b) comprises reacting an acryloxy-substituted alkyldimethylalkoxysilane with acetyl chloride and a weak Lewis acid catalyst.

12. 12. The method of any one of claims 7 to 11, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and the product of step (a) is a (meth)acryloxyalkyldimethylalkoxysilane.

13. 13. The method according to any one of claims 7 to 12, wherein the acryloxyalkyldimethylchlorosilane is 3-methylacryloxypropyldimethylchlorosilane, methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, or 3-(methacryloxy)propylmethyldichlorosilane.

14. 14. The method of any one of claims 7 to 13, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99%.

15. 15. The method of any one of claims 7 to 14, wherein the acryloxyalkyldimethylchlorosilane has a purity of greater than about 99.3%.

16. 16. The method of any one of claims 7 to 15, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.1% by weight of hydrogenation by-products and less than about 0.1% by weight of isomeric by-products.

17. 17. The method of any one of claims 7 to 16, wherein the acryloxyalkyldimethylchlorosilane contains less than about 0.05% by weight hydrogenation by-products and less than about 0.05% isomeric by-products.

18. 18. The method of any one of claims 7 to 17, wherein the acryloxyalkyldimethylchlorosilane is a (meth)acryloxyalkyldimethylchlorosilane and contains less than about 0.05% by weight isobutyloxypropyldimethylchlorosilane and less than about 0.05% by weight 1-methyl-2-methacryloxyethyldimethylchlorosilane.

19. 7. A method for synthesizing a high purity (meth)acryloxyalkyldimethyl-functional polysiloxane macromer, comprising the steps of carrying out a living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as a starting material and an acryloxyalkyldimethylchlorosilane as claimed in any one of claims 1 to 6 as a terminating reagent.

20. 20. The method of claim 19, wherein the polysiloxane is monomethacryloxypropyl terminated polydimethylsiloxane.

21. 21. The method of claim 19 or 20, wherein the polysiloxane is substantially free of non-polymeric polysiloxanes.

22. 22. The method according to any one of claims 19 to 21, wherein the polysiloxane contains less than about 0.1% by weight of impurities containing hydrogenated derivatives or isomers of (meth)acryloxyalkyl functional groups.

23. A methacrylate-functional macromer or copolymer derived from an acryloxyalkyldimethylchlorosilane having a purity of at least about 99%.

24. 24. The macromer or copolymer of claim 23 containing less than about 0.1% by weight of hydrogenated derivatives of methacrylate functional groups.

25. 25. The macromer or copolymer of claim 23 or 24 containing less than about 0.05% by weight of hydrogenated derivatives of methacrylate functional groups.

26. 26. The macromer or copolymer of any one of claims 23 to 25 having a molecular weight of less than about 5,000 daltons.

27. 27. A methacrylate-functional macromer or copolymer having a purity of at least about 99.3% and derived from an acryloxyalkyldimethylchlorosilane as defined in any one of claims 23 to 26.

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