TWI904300B - High purity polysiloxane macromers and method for making the same - Google Patents

Abstract

A method of synthesizing a high purity acryloxyalkyldimethylchlorosilane involves (a) reacting an acrylate salt with a haloalkyldimethylalkoxysilane to form an acryloxy-substituted alkyldimethylalkoxysilane; and (b) displacing the alkoxy group in the acryloxy-substituted alkyldimethylalkoxysilane using a chloride-containing compound to form the acryloxyalkyldimethylchlorosilane. The acryloxyalkyldimethylchlorosilane, which may be used as an end-capper for AROP, has a purity of greater than about 99% and contains no detectable isomeric or hydrogenated impurities.

Description

High-purity polysiloxane macromonomers and their manufacturing methods

Invention field

This invention relates to high-purity polysiloxane macromolecular monomers and their manufacturing method.

Invention Background

Acrylic-functionalized polysiloxane macromonomers continue to find applications, where precise control of their mechanical, optical, or electrical properties is crucial for their final use. The most common silicate macromonomer is mono-methacryloxypropyl-terminated polydimethylsiloxane, most commonly known as MPDMS or MCR-M11, and has the formula (1).

Impurities found in acrylate-functionalized polysiloxane macromonomers often have detrimental effects on end applications. Similar problems occur in variants of the most commonly used macromonomers, including, for example, macromonomers comprising a trifluoropropyl-substituted backbone and macromonomers with symmetrical structures, such as those having formulas (2) and (3).

For example, isomeric impurities lead to heterogeneity in the copolymer structure, and inert impurities may result in extractable species, which may affect biocompatibility or cause domain segregation that affects the optical properties of the copolymer.

Polysiloxane macromonomers are formed via anionic ring-opening polymerization (AROP). Goff et al. describe this chemical process (see “Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization,” Molecules , 26, 2755 (2021)). During the polymerization of these silica-containing macromonomers, conditions that prevent redistribution reactions are crucial for achieving purity, but most of these variables are now understood. The most significant limitation to achieving high purity is the “capping agent” or “terminating” reagent used in the AROP reaction: 3-(methacryloyloxy)propyldimethylchlorosilane, which has formula (4).

This end-capping agent material is conventionally produced by the hydrogenation and silanization of allyl methacrylate. The earliest discontinuous synthesis of this product was reported by Cameron ( Polymer , 26, 437 (1985)), with a yield of 50%, but the final purity was not specified. Unfortunately, the reaction was not pure, and the reaction mixture was not easily purified, not only because the products had similar boiling points, but also because of the tendency to polymerize during processing. A major byproduct is the β-isomer, 1-methyl-2-methacryloxyethyl dimethylchlorosilane (Formula (5)).

Other byproducts include the hydrogenated analogues of the desired 3-(methacryloxy)propyl dimethylchlorosilane and the hydrogenated analogues of the β-isomer. The hydrogenated analogue of the desired product is isobutyryloxypropyl dimethylchlorosilane, having formula (6).

These impurities arise from the selectivity of the hydrogenation silylation catalyst, which, while favoring the anti-Markovnikov addition product, also allows the formation of the normal Markovnikov product, permits secondary dehydrogenation coupling reactions, and catalyzes the hydrogenation of the acrylate double bonds. This hydrogenation silylation is preferred, but not limited to the allyl group, and to a lesser extent, occurs with the unsaturation of the acrylate. Although allyl unsaturation exists in the product formed by the hydrogenation silylation of the acrylate double bonds, it is essentially unreactable under normal polymerization conditions, resulting in the extractability of the macromonomers derived from this byproduct. For example, unlike methacrylate-functionalized macromonomers, allyl-functionalized macromonomers are not readily photoinitiated polymerizes.

Furthermore, a major byproduct formed by the elimination of propylene is methacryloxydimethylchlorosilane (formula (8)), which can undergo an exchange reaction with silicon-bound chlorine to produce a compound having formula (9).

The description of impurities is not exhaustive, but rather highlights the many problems and difficulties involved in producing high-purity macromonomers from acryloxy-functionalized end-capping agents generated by hydrogenation silylation.

Besides the obvious structural impurities caused by the incorporation of structural analogs of the end-capping agent into the desired macromolecular monomer, it is also difficult to determine the exact amount of end-capping agent required to achieve molecular weight control. Obtaining high yield and high purity of the end-capping agent is crucial for both economic efficiency and performance.

A method for obtaining 3-(methacryloxy)propyldimethylchlorosilane in higher yields was reported by Cracknell (WO 2016/005757), in which byproducts were minimized by a process control method utilizing the same basic chemistry. However, the purity of the separated product was reported to be only 89%, and no isomer or hydrogenation byproducts were identified or reported. A more detailed synthesis is reported in U.S. Patent No. 5,847,178 to Okawa and U.S. Patent No. 5,811,565 to Mikami, demonstrating that a purity of up to 98.9% can be achieved in a subsequent synthesis step by adding a copper reagent to decompose the β-isomer. Recently, Nishiwaki's JP 2003-096086 describes the use of an iridium catalyst, which also results in a purity of 98.9%. It should be noted that only one earlier reported synthesis (Okawa's U.S. Patent No. 5,493,039) serves as a baseline or a reduction of a reducing analogue of the target compound, which is isobutyryloxypropyl dimethylchlorosilane (also known as α-methylpropyloxypropyl dimethylchlorosilane), presumably because this product cannot be identified using older gas chromatography techniques. Furthermore, all earlier literature reports regarding high purity may be exaggerated, at least because at the time these references appeared, the analytical limits typically lacked the sensitivity to determine hydrogenation and isomer byproducts, and the failure to meet performance criteria seemed inexplicable.

These reduction byproducts are particularly problematic because they introduce non-polymerizable, extractable impurities into products derived from nominally pure methacrylate-functionalized polysiloxane macromonomers. To date, no method has been developed via hydrogenation silylation or any other reactive pathway to produce methyl(acryloxy)alkyldimethylchlorosilanes free of isomer or hydrogenation byproducts, making them suitable for critical applications. For example, in optical applications such as contact lenses, these types of impurities can cause loss of transparency and eye irritation by allowing the migration, phase separation, or extraction of non-reactive polymerizable species as contaminants within another fully polymerizable macromonomer. Therefore, it is highly desirable to produce acryloxyalkyl dimethylchlorosilanes in high yields without detectable isomer or hydrogenation byproducts.

Invention Summary

In one embodiment disclosed herein, an acryloxyalkyl dimethylchlorosilane is provided, having a purity of at least about 99% and containing less than about 0.1 wt.% of hydrogenation byproducts and less than about 0.1 wt.% of isomer byproducts.

In another embodiment of this disclosure, a method for synthesizing a high-purity acryloxyalkyl dimethylchlorosilane is provided, comprising: (a) reacting an acrylate with a halogenated dimethylalkoxysilane to form an acryloxy-substituted alkyl dimethylalkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyl dimethylalkoxysilane with a chloride-containing compound to form the acryloxyalkyl dimethylchlorosilane.

In a further embodiment of this disclosure, a methacrylate-functionalized macromonomer or copolymer derived from acryloxyalkyl dimethylchlorosilane is provided, wherein the macromonomer or copolymer has a purity of at least about 99%.

The advantageous improvements of the invention are described in those supplementary claims, which may be practiced individually or in combination.

In summary, within the scope of this invention, the following preferred embodiments are proposed:

Embodiment 1: An acryloxyalkyl dimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1 wt.% of hydrogenation byproducts and less than about 0.1 wt.% of isomer byproducts.

Embodiment 2: Acryloyloxyalkyl dimethylchlorosilane as in Embodiment 1, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of hydrogenation byproducts and less than about 0.05 wt.% of isomer byproducts.

Embodiment 3: An acryloxyalkyl dimethylchlorosilane as in Embodiment 1 or 2, wherein the acryloxyalkyl dimethylchlorosilane is (methyl)acryloxyalkyl dimethylchlorosilane.

Embodiment 4: As in Embodiment 3, an acryloxyalkyl dimethylchlorosilane, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of isobutyryloxypropyl dimethylchlorosilane and less than about 0.05 wt.% of 1-methyl-2-methylacryloxyethyl dimethylchlorosilane.

Embodiment 5: an acryloxyalkyl dimethylchlorosilane as described in any of the foregoing embodiments, wherein the purity is greater than about 99.3%.

Embodiment 6: An acryloxyalkyl dimethylchlorosilane as described in any of the foregoing embodiments, wherein the acryloxyalkyl dimethylchlorosilane is 3-methacryloxypropyl dimethylchlorosilane, methacryloxymethyl dimethylchlorosilane, 3-(acryloxy)propyl dimethylchlorosilane, 11-(methacryloxy)undecyl dimethylchlorosilane, or 3-(methacryloxy)propylmethyl dichlorosilane.

Embodiment 7: A method for synthesizing high-purity acryloxyalkyl dimethylchlorosilane, comprising: (a) reacting an acrylate with a halogenated dimethylalkoxysilane to form an acryloxy-substituted alkyl dimethylalkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyl dimethylalkoxysilane with a chloride-containing compound to form the acryloxyalkyl dimethylchlorosilane.

Embodiment 8: The method is the same as that of Embodiment 7, wherein step (a) is a phase-transfer catalytic reaction.

Embodiment 9: The method of Embodiment 7 or 8, wherein step (a) comprises (i) reacting a halide salt with methacrylic acid to form the acrylate; and (ii) reacting the acrylate with the halogenated dimethylalkoxysilane.

Example 10: The method as described in any of Examples 7 to 9, wherein step (b) is an exchange or substitution reaction.

Embodiment 11: The method of any of Embodiments 7 to 10, wherein step (b) comprises reacting the acryloxy-substituted alkyl dimethylalkoxysilane with acetyl chloride and a weak Lewis acid catalyst.

Embodiment 12: The method of any of Embodiments 7 to 11, wherein the acryloxyalkyl dimethylchlorosilane is (meth)acryloxyalkyl dimethylchlorosilane, and the product of step (a) is (meth)acryloxyalkyl dimethylalkoxysilane.

Embodiment 13: The method of any of Embodiments 7 to 12, wherein the acryloxyalkyl dimethylchlorosilane is 3-methacryloxypropyl dimethylchlorosilane, methacryloxymethyl dimethylchlorosilane, 3-(acryloxy)propyl dimethylchlorosilane, 11-(methacryloxy)undecyl dimethylchlorosilane, or 3-(methacryloxy)propylmethyl dichlorosilane.

Embodiment 14: The method of any of Embodiments 7 to 13, wherein the acryloxyalkyl dimethylchlorosilane has a purity greater than about 99%.

Embodiment 15: The method of any of Embodiments 7 to 14, wherein the acryloxyalkyl dimethylchlorosilane has a purity greater than about 99.3%.

Embodiment 16: The method of any of Embodiments 7 to 15, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.1 wt.% of hydrogenation byproducts and less than about 0.1 wt.% of isomer byproducts.

Embodiment 17: The method of any of Embodiments 7 to 16, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of hydrogenation byproducts and less than about 0.05% of isomer byproducts.

Embodiment 18: The method of any of Embodiments 7 to 17, wherein the acryloxyalkyl dimethylchlorosilane is (meth)acryloyloxyalkyl dimethylchlorosilane and contains less than about 0.05 wt.% of isobutyrylooxypropyl dimethylchlorosilane and less than about 0.05 wt.% of 1-methyl-2-methylacrylooxyethyl dimethylchlorosilane.

Embodiment 19: A method for synthesizing high-purity (meth)acryloyloxyalkyl dimethyl functional polysiloxane macromonomers, said method comprising using hexamethylcyclotrisiloxane as a starting material and acryloxyalkyl dimethylchlorosilane according to any one of embodiments 1 to 6 as a terminating agent for performing living anionic ring-opening polymerization.

Embodiment 20: The method of Embodiment 19, wherein the polysiloxane is a monomethacryloyloxypropyl-terminated polydimethylsiloxane.

Embodiment 21: The method of Embodiment 19 or 20, wherein the polysiloxane substantially does not contain non-polymerizable polysiloxane.

Embodiment 22: The method of any of Embodiments 19 to 21, wherein the polysiloxane contains less than about 0.1 wt.% impurities, said impurities being hydrogenated derivatives or isomers of the (meth)acryloxyalkyl functional group.

Embodiment 23: A methacrylate functional macromonomer or copolymer derived from acryloxyalkyl dimethylchlorosilane, wherein the macromonomer or copolymer has a purity of at least about 99%.

Embodiment 24: A macromonomer or copolymer as in Embodiment 23, wherein the macromonomer or copolymer contains less than about 0.1 wt.% of the methacrylate-functionalized hydrogenated derivative.

Embodiment 25: A macromonomer or copolymer as in Embodiment 23 or 24, wherein the macromonomer or copolymer contains less than about 0.05 wt.% of the methacrylate-functionalized hydrogenated derivative.

Embodiment 26: A macromonomer or copolymer of any of embodiments 23 to 25, having a molecular weight of less than about 5,000 Daltons.

Embodiment 27: A methacrylate functional macromonomer or copolymer derived from acryloxyalkyl dimethylchlorosilane, as in any of Embodiments 23 to 26, wherein the macromonomer or copolymer has a purity of at least about 99.3%.

Detailed description of this invention

This disclosure relates to a method for synthesizing high-purity acryloxyalkyl dimethylchlorosilanes, which are suitable end-capping agents for active AROPs. These high-purity compounds are substantially free of isomers and hydrogenation byproducts, and allow for the preparation of high-purity acryloxyalkyl-terminated poly(siloxanes) that are substantially free of non-polymerizable polysiloxanes. The method disclosed avoids the hydrogenation and silylation of acrylates, instead utilizing a substitution reaction in which no isomerization or reduction chemical mechanism exists. In a preferred embodiment, the capping agent produced by this method is 3-methacryloxypropyl dimethylchlorosilane (formula (4)), which has a purity of about 99% or higher and is free from detectable hydrogenated analogues (isobutyryloxypropyl dimethylchlorosilane, having formula (6)) or the β-isomer (1-methyl-2-methacryloxyethyl dimethylchlorosilane, having formula (5)). This high-purity compound can be used as a capping agent or terminator for the production of monomethacryloxypropyl-capped polydimethylsiloxanes. Other examples of high-purity compounds suitable as capping or terminating agents for the synthesis of active AROPs from macromolecular monomers include (methacryloxymethyl)dimethylchlorosilane and 3-(acryloxymethyl)dimethylchlorosilane, which have not yet been synthesized.

In all cases, the compounds described herein are substantially free of isomer byproducts/reduction analogs and hydrogenation byproducts/reduction analogs. The negative effects of impure end-capped compounds are most pronounced when the molecular weight of these macromonomers is relatively low, particularly less than about 5,000 Daltons. At higher molecular weights, nonreactive macromonomers formed from reduction analogs can be dissolved in a final polymer, where the macromonomer forms pendant groups in a copolymer. For copolymers derived from low molecular weight macromonomers, light transmission loss may occur due to phase separation of the reduction analog. The materials and methods described herein address the optical defects associated with low molecular weight macromonomers incorporated as comonomers into polymers used to form contact lenses.

For the purposes of this disclosure, the term "high purity" can be understood as meaning a purity greater than about 99%, more preferably greater than about 99.2%, and even more preferably greater than about 99.3%. The term "substantially absent" can be understood as meaning that impurities cannot be detected by GC and GC-MS, which typically have detection limits of less than about 0.05 wt.%. Therefore, this method provides the synthesis of acryloxyalkyl dimethylchlorosilanes having high purity and also lacking detectable isomer byproducts or hydrogenation byproducts, i.e., less than about 0.1 wt.% or less than about 0.05 wt.% of isomer byproducts or hydrogenation byproducts. Other impurities that may be present have almost no effect on the properties of AROP or the resulting macromolecular monomers.

A method for synthesizing the high-purity acryloxyalkyl dimethylchlorosilane includes (a) forming an acryloxy-substituted alkyl dimethylalkoxysilane, preferably by a phase-transfer catalytic reaction between an acrylate and a (halogenated) dimethylalkoxysilane, and then (b) replacing the alkoxy group with a halogen, preferably in an exchange or substitution reaction. In step (a), a preferred acrylate is potassium methacrylate, which can be generated in situ, for example, by the reaction of potassium carbonate with methacrylic acid. A preferred (halogenated) dimethylalkoxysilane is 3-chloropropyldimethylethoxysilane. Alternatively, but less preferably, acrylic acid can react with the halogenated silane in the presence of a base acceptor. However, this chemical reaction cannot directly produce the preferred methacryloxypropyl dimethylchlorosilane because the acrylate also reacts with the silicon-bound chlorine. Therefore, the formation of methacryloxypropyl dimethylalkoxysilane has been found to be a practical intermediate. In a preferred embodiment, the high-purity end-capping agent is (meth)acryloxypropyl dimethylchlorosilane, and the intermediate is (meth)acryloxypropyl dimethylethoxysilane.

Many known synthetic methods can be used to convert the alkoxy group bound to silicon in the second reaction step (b) into a halogen. For example, the ethoxy group on silicon can be exchanged for chlorine by reacting with thionyl chloride, phosphorus trichloride, phosphorus pentachloride, benzyl chloride, boron trichloride, tin tetrachloride, methyltrichlorosilane, or acetyl chloride, etc. The most commonly used reagents are thionyl chloride and phosphorus pentachloride, which can additionally cleave acrylate to form acetyl chloride, and both are used as initiators for polymerization (see T. Sengupta et al, Journal of the Indian Chemical Society ; 53: 7,726-7 (1976)). Benzyl chloride and acetyl chloride are less effective in exchange or substitution reactions unless catalyzed in the presence of a strong Lewis acid catalyst such as aluminum trichloride or boron trichloride. However, strong Lewis acids have the potential to catalyze reactions involving the functionality of the acrylate. Currently, a preferred reaction pair for this exchange reaction is acetyl chloride with a weak Lewis acid catalyst, preferably ferric chloride, which does not cleave the acrylate or induce polymerization.

The above-described synthetic methods are generally applicable to the production of analogues and homologues of 3-methacryloxypropyl dimethylchlorosilane, wherein the purity is greater than about 99%, more preferably greater than about 99.2%, and even more preferably greater than about 99.3%, and there is no detectable isomer or hydrogenation byproduct contamination, and are suitable for the synthesis of high-purity acrylate functional macromolecular monomers. Other examples of compounds with similar functional structures that can be produced with high purity using the methods described herein, without detectable isomer byproducts and hydrogenation byproducts, include methacryloxymethyldimethylchlorosilane, 3-(acryloxy)propyldimethylchlorosilane, 11-(methacryloxy)undecyldimethylchlorosilane, and 3-(methacryloxy)propylmethyldichlorosilane. Although similar bromosilanes can be prepared by similar methods, their lower utility is primarily due to economic reasons.

Another indirect indicator of the purity of the end-capping agent produced in this manner is the observation that a smaller excess of end-capping agent than the theoretical stoichiometric amount is required to terminate these living AROP polymerizations. For example, when the end-capping agent is conventionally produced by hydrogen silanization, a 2% excess of end-capping agent is required, while the high-purity end-capping agent described herein only requires a 1% excess to terminate the polymerization.

This disclosure also relates to methods for producing high-purity (meth)acryloxyalkylmethylsiloxane macromonomers and copolymers derived from the aforementioned high-purity (meth)acryloxyalkylmethyldichlorosilane. The asymmetric macromonomers are typically prepared by initiating polymerization with lithium dimethylsilanol, which is formed by the reaction of an alkyl lithium reagent with a strainable cyclic silicate, the most common strainable cyclic silicate being hexamethylcyclotrisiloxane. The lithium silanol can be isolated or formed in situ. In the presence of a strain-dependent cyclic siloxane and an accelerator, typically an aprotic polar material such as dimethylformamide or tetrahydrofuran, the ring-opening polymerization of the additional strain-dependent cyclic siloxane continues. Finally, the polymer is capped with a monochlorosilane, such as the most commonly used 3-(methacryloyloxy)propyldimethylchlorosilane, to complete the formation of the macromonomer. Symmetrical macromonomers are formed in a similar manner, but the dichlorosilane couples rather than terminates the reaction. These macromolecular monomers 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 wt.% hydrogenated impurities and less than about 0.1 wt.% isomer impurities, and have a molecular weight of less than about 5,000 Daltons, more preferably less than about 1,000 Daltons.

A further aspect of this disclosure relates to a method for producing high-purity (meth)acrylate functionalized macromonomers derived from high-purity end-capping agents, including meth(acryloyloxy)methyl end-capping macromonomers that have never been prepared before. Specifically, these macromonomers can be produced using the AROP process well known in the art and using the high-purity end-capping agent described herein.

For example, a method for synthesizing a high-purity (meth)acryloxyalkyl dimethyl functional asymmetric polysiloxane macromonomer includes a living anionic ring-opening polymerization using hexamethylcyclotrisiloxane as a starting material and the aforementioned acryloxyalkyl dimethylchlorosilane as a capping agent. In a preferred embodiment, the polysiloxane is a monomethacryloxypropyl-terminated polydimethylsiloxane. The resulting polysiloxane substantially does not contain non-polymerizable polysiloxanes and contains less than about 0.1 wt.% impurities (or less than about 0.05 wt.% in a preferred embodiment), said impurities being hydrogenated derivatives or isomers of the (meth)acryloxyalkyl functionality. Similarly, symmetrical polysiloxane macromonomers can be derived from 3-(methacryloyloxypropyl)methyldichlorosilane.

The present invention will now be described in conjunction with the following non-limiting embodiments.

Example 1 (Comparative): Synthesis of Methacryloxypropyldimethylchlorosilane

Allyl methacrylate (1261 g, 10.0 mol) and BHT (4 wt%, 83.9 g) were loaded into a reactor, and _O₂ /Ar spraying was initiated. The reaction mixture was heated to 75 °C, and then Karstedt catalyst (2% Pt concentration in xylene, 1 ml) was added. Dimethylchlorosilane (969.8 g, 10.3 mol) was added dropwise over 6 hours while maintaining the boiler temperature between 65 and 85 °C. The resulting reaction mixture was stirred at 80 °C for 1 hour. Phenothiazine (5 wt%) was added to the reaction mixture, and purification was performed using a wiped film evaporator to obtain a clear, colorless liquid (1100 g, 50%). Analysis data: ^¹H NMR (400MHz, _CDCl₃ ) δ 6.10(s, ¹H), 5.56(s, ¹H), 4.15–4.12(t, J = 7.2Hz, 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-Isomers -2.01%, Isobutyroxylpropyl dimethylchlorosilane -0.88%; GC-MS m/z : 220 (M), 205 (M-Me). When the hydrolysis (diasiloxane) product formed during the analysis was added back to remove the pseudodiasiloxane formed during sample processing, the purity of the product was 89.7%.

Example 2: Synthesis of 3-methylpropenoxypropyldimethylethoxysilane

A 2L four-necked flask was equipped with a mechanical stirrer, a heating mantle, an addition funnel, a boiler heat probe, a sintered glass dispersion tube, and a Dean-Stark trap with a water-cooled condenser. Di-tertiary butylhydroxytoluene (BHT) (4.19 g, 3.50 wt%) and toluene (960 g) were charged into the reactor. Stirring was initiated, and potassium carbonate (109.1 g, 7.67 mol) was added. The slurry was heated to 80°C using an _O₂ /Ar jet, and then methacrylic acid (119.9 g, 1.40 mol) was added dropwise at 100°C for 2 hours. Carbon dioxide gas was observed to escape, and water was removed under reflux conditions using the Dean-Stark trap. An azeotropic reaction was observed at 90°C. After removing all aqueous byproducts, 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 under reflux for 3 hours and then cooled to room temperature. The reaction mixture was filtered. The filtrate was concentrated under vacuum, and 5 wt% phenothiazine was added. The product was then purified by scraped film evaporation under a vacuum of 0.6-0.7 mmHg, with a jacket temperature of 64-5°C, a cold finger temperature of 30°C, and a product:residue split of 4:1, to obtain the final product 3-methacryloxypropyldimethylethoxysilane (202.6 g, 66.2%) as a transparent, colorless liquid. Analysis data: ^¹H NMR (400MHz, _CDCl₃ ) δ 6.08(s, ¹H), 5.55(s, ¹H), 4.07–4.10(t, J = 7.2Hz, ²H), 3.61–3.66(q, J = 13.6Hz, ²H), 1.91(s, ³H), 1.63–1.73(m, ²H), 1.12–1.20(t, J = 6.8Hz, ³H), 0.6(m, ²H), 0.09(s, ⁶H); FTIR ( ^cm⁻¹ ) GC-TCD: Purity -99.3%; GC-MS m/z: 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-isomers and isobutyryloxypropyldimethylethoxysilane were both below the detection levels by GC and GC-MS using a capillary column, i.e., less than 0.05%.

Example 3: Synthesis of 3-methylpropenoxypropyl dimethylchlorosilane

A 1L four-necked reactor is equipped with a magnetic stirrer, a boiler hot probe, a cooling bath, an addition funnel, a packed column, and a distillation head with _N2 . Anhydrous ferric chloride (1.40 g, 0.01 mol) and acetyl chloride (123.6 g, 1.58 mol) are loaded into the reactor. 1 wt% BHT (345.5 g, 1.50 mol) is used to suppress 3-methacryloxypropyldimethylethoxysilane prepared in Example 2, and phenothiazine (1.50 g, 0.01 mol) is added dropwise to the reaction mixture at a rate maintaining the reaction temperature at 20 to 25°C. An exothermic reaction is observed, and the color of the mixture changes from yellow to brown. (A temperature rise of 30-40°C was observed when the reaction was carried out without a cooling bath.) The resulting reaction mixture was stirred at room temperature for 12 hours. The mixture was then concentrated under vacuum at a maximum temperature of 80°C at 5 mmHg and purified by scraped-film evaporation (using 5 wt% phenothiazine, 45-48°C, 0.5 mmHg, cold index -25°C, split -3:1) to obtain a product as a clear, colorless liquid (270.4 g, 81.7%). GC-TCD: Purity 98.91%. The purity of the product was 99.3% when the hydrolysis (disiloxane) product formed during analysis was added back to remove the pseudodisiloxane formed during sample processing. BHT (4wt%) was added to the final product as an inhibitor. Analysis data: ^¹H NMR (400MHz, _CDCl₃ ) δ 6.10(s, ¹H), 5.56(s, ¹H), 4.15–4.12(t, J = 7.2Hz, 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). No detection limit of 0.05% was observed in isobutyryloxypropyl dimethylchlorosilane and 1-methyl-2-methylpropenyloxyethyl dimethylchlorosilane.

Example 4: Synthesis of (methacryloxymethyl)dimethylethoxysilane

A 22L four-necked flask is equipped with a mechanical stirrer, heating mantle, adding funnel, boiler heat probe, sintered glass dispersion tube, and distillation head mounted on a 500cm packed column. 3000ml of cyclohexane and 3718g of a 32% potassium methanol solution in methanol are added to the flask. Stirring and air jetting below the liquid level are initiated. Methacrylic acid (1439ml, inhibited with BHT) is added through the adding funnel, maintaining the temperature below 60°C. After addition, the pH is >9. The flask is then heated to remove methanol. When the boiler temperature reaches 71-73°C, methanol is removed from the boiler, and the cyclohexane in the Dean-Stark separator is clear. Approximately 100 ml of clear cyclohexane was not returned to the boiler. After all methanol was removed and the flask was cooled to room temperature, chloromethyldimethylethoxysilane (2119 ml) was added to the flask through the addition funnel, followed by 69.7 g of tetrabutylammonium bromide. The flask was heated to 80-90°C for 20 hours, during which time all the reactants had reacted. After the reaction was complete, the mixture was filtered, the salts were washed twice with 1 L of cyclohexane, and the filtrate was concentrated. 1 g of methyl ether of hydroquinone (MEHQ) and 1 g of phenothiazine were added to the concentrate. The product was distilled through a 0.25 m packed column at 62-4°C under a vacuum of 0.3 mmHg. The product was suppressed using 20 ppm MEHQ for storage at <5°C.

Example 5: Synthesis of (methacryloxymethyl)dimethylchlorosilane

Under conditions similar to those of Example 3, (methacryloxymethyl)dimethylchlorosilane was prepared from the product of Example 4. A 500 mL four-necked flask was equipped with a magnetic stirrer, a boiler hot 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 added to the reactor. A premixture of 3-methacryloxymethyldimethylethoxysilane (101 g, 0.50 mol) and phenothiazine (0.5 g, 0.5 wt%) was added dropwise to the reaction mixture at a rate maintaining the reaction temperature between 20 and 25 °C. The 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 hours. The mixture was vacuum concentrated using _O₂ /Ar spraying, and 0.5 wt% phenothiazine was added. The product was purified by distillation at 3-4 mmHg and 57-59 °C to obtain the final product 3-methacryloxymethyldimethylchlorosilane (22.0 g, 22.8%) as a transparent, colorless liquid. Analytical data: ^¹H NMR (400 MHz, _CDCl₃ ) δ 6.12 (s, 1H), 5.62 (s, 1H), 2.98 (s, 2H), 1.89 (s, 3H), 0.42 (s, 6H); 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-Cl). The level of isobutyric acid methyl dimethyl chlorosilane was lower than the detection level by GC and GC-MS using a capillary column, i.e., less than 0.1%.

Example 6: Synthesis of monobutyl-, monomethacryloxypropyl-terminated polydimethylsiloxanes

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 stirrer. The flask was purged with nitrogen, and the reaction mixture was stirred at room temperature for 2 hours. n-Butyllithium (2.6 M in hexane, 69.3 g, 0.26 mol) was added to the reaction flask via an addition funnel, and the solution was stirred for 1 hour. Then, dimethylformamide (DMF, 18.2 g, 0.25 mol) was added to the solution as a polymerization accelerator. After stirring for 3 hours, the polymer was capped with 3-methacryloxypropyldimethylchlorosilane (prepared in Example 3) to obtain monobutyl-,monomethacryloxypropyl-capped polydimethylsiloxane. The solution was then stirred overnight and washed with 178 g of deionized water. The aqueous layer and the organic layer were separated, and the organic layer was dried with sodium sulfate, filtered, and stripped under vacuum at 95°C with dry air.

Example 7: Comparison of comparative products and the product of the present invention

The macromonomers derived from 3-methacryloxypropyl dimethylchlorosilane (compare, Example 1) produced by hydrogenation silanization and the macromonomers derived from the high-purity material of the present invention prepared in Example 3 are analyzed and compared in the table below:

Comparative Implementation Example 8: Implementation Example 1 of Okawa's U.S. Patent No. 5,493,039

3-Methylpropyltrimethylchlorosilane was synthesized under the same conditions and scale as described in Example 1 of U.S. Patent No. 5,493,039 to Okawa, except that the water content of the allyl methacrylate was 37 ppm instead of 171 ppm. Analysis of the product showed the presence of isobutyroxypropyltrimethylchlorosilane (0.59%) and the β-isomer (1.47%). The purpose of this comparative example is to demonstrate that, although not reported by Okawa, the reduced product was actually generated during this hydrogenation silylation process. The level of isobutyroxymethyltrimethylchlorosilane was lower than the level detected by GC and GC-MS using a capillary column, i.e., less than 0.05%.

Comparative Implementation Example 9: Actual Implementation Example 1 of Mikami's U.S. Patent No. 5,811,565

3-Methylpropyltrimethylchlorosilane was synthesized as described in Example 1 of U.S. Patent No. 5,811,565 to Mikami, except that phenothiazine was used instead of 3,5-di-tert-butyl-4-hydroxyphenylmethyldimethylammonium chloride as an inhibitor, and the reaction mixture was sprayed with _O₂ /Ar during hydrogenation silylation. Analytical data prior to the addition of the copper reagent showed the presence of both isobutyroxypropyltrimethylchlorosilane (0.26%) and the β-isomer (1.87%). After the addition of copper(II), a decrease in the β-isomer content to below 1.0% was observed, but no change in the isobutyroxypropyltrimethylchlorosilane content was observed. The purpose of this comparative example is to demonstrate that, although MiKami did not report it, the reduction product was actually generated during this hydrogenation silylation process. The level of isobutyric acid methyl dimethylchlorosilane was lower than the detection level by GC and GC-MS using a capillary column, i.e., less than 0.05%.

It can be clearly observed that the 3-methacryloxypropyl dimethylchlorosilane prepared according to the method of the present invention not only possesses significantly higher purity than similar materials prepared by conventional hydrogenation silylation, but also lacks detectable β-isomers or hydrogenation byproducts. Furthermore, when this compound is used as an end-capping agent for AROP, the required excess percentage is reduced by half.

Those skilled in the art will understand that modifications can be made to the above embodiments without departing from their broad inventive concept. Therefore, it should be understood that this invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as defined in the appended invention claims.

Claims (27)

An acryloxyalkyl dimethylchlorosilane having a purity of at least about 99% and containing less than about 0.1 wt.% of hydrogenation byproducts and less than about 0.1 wt.% of isomer byproducts. The acryloxyalkyl dimethylchlorosilane of claim 1, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of hydrogenation byproducts and less than about 0.05 wt.% of isomer byproducts. Such as the acryloxyalkyl dimethylchlorosilane in claim 1 or 2, wherein the acryloxyalkyl dimethylchlorosilane is (methyl)acryloxyalkyl dimethylchlorosilane. The acryloxyalkyl dimethylchlorosilane of claim 3, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of isobutyryloxypropyl dimethylchlorosilane and less than about 0.05 wt.% of 1-methyl-2-methylacryloxyethyl dimethylchlorosilane. The acryloxyalkyl dimethylchlorosilane of any one of claims 1, 2 or 4, wherein the purity is greater than about 99.3%. The acryloxyalkyl dimethylchlorosilane in any of claims 1, 2, or 4, wherein the acryloxyalkyl dimethylchlorosilane is 3-methacryloxypropyl dimethylchlorosilane, methacryloxymethyl dimethylchlorosilane, 3-(acryloxy)propyl dimethylchlorosilane, 11-(methacryloxy)undecyl dimethylchlorosilane, or 3-(methacryloxy)propylmethyl dichlorosilane. A method for synthesizing high-purity acryloxyalkyl dimethyl chlorosilane comprises: (a) reacting an acrylate with a halogenated dimethyl alkoxysilane to form an acryloxy-substituted alkyl dimethyl alkoxysilane; and (b) replacing the alkoxy group in the acryloxy-substituted alkyl dimethyl alkoxysilane with a chloride-containing compound to form the acryloxyalkyl dimethyl chlorosilane. The method of claim 7, wherein step (a) is a phase transfer catalytic reaction. The method of claim 7 or 8, wherein step (a) comprises (i) reacting the halogen salt with methacrylic acid to form the acrylate; and (ii) reacting the acrylate with the halogenated dimethylalkoxysilane. As in the method of claim 7 or 8, step (b) is an exchange or substitution reaction. The method of claim 7 or 8, wherein step (b) comprises reacting the acryloxy-substituted alkyl dimethylalkoxysilane with acetyl chloride and a weak Lewis acid catalyst. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane is (meth)acryloxyalkyl dimethylchlorosilane, and the product of step (a) is (meth)acryloxyalkyl dimethylalkoxysilane. As in the method of claim 7 or 8, wherein the acryloxyalkyl dimethyl chlorosilane is 3-methacryloxypropyl dimethyl chlorosilane, methacryloxymethyl dimethyl chlorosilane, 3-(acryloxy)propyl dimethyl chlorosilane, 11-(methacryloxy)undecyl dimethyl chlorosilane, or 3-(methacryloxy)propylmethyl dichlorosilane. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane has a purity greater than about 99%. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane has a purity greater than about 99.3%. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.1 wt.% of hydrogenation byproducts and less than about 0.1 wt.% of isomer byproducts. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane contains less than about 0.05 wt.% of hydrogenation byproducts and less than about 0.05% of isomer byproducts. The method of claim 7 or 8, wherein the acryloxyalkyl dimethylchlorosilane is (methyl)acryloxyalkyl dimethylchlorosilane and contains less than about 0.05 wt.% of isobutyryloxypropyl dimethylchlorosilane and less than about 0.05 wt.% of 1-methyl-2-methylacryloxyethyl dimethylchlorosilane. A method for synthesizing high-purity (meth)acryloyloxyalkyl dimethyl functional polysiloxane macromonomers, the method comprising using hexamethylcyclotrisiloxane as a starting material and acryloxyalkyl dimethylchlorosilane as claimed in any of claims 1 to 6 as a terminating agent for performing living anionic ring-opening polymerization. The method of claim 19, wherein the polysiloxane is a monomethacryloxypropyl-terminated polydimethylsiloxane. The method of claim 19 or 20, wherein the polysiloxane does not substantially contain nonpolymeric polysiloxane. The method of claim 19 or 20, wherein the polysiloxane contains less than about 0.1 wt.% of impurities, said impurities being (meth)acryloxyalkyl functional hydrogenated derivatives or isomers. A methacrylate functional macromonomer or copolymer derived from acryloxyalkyl dimethylchlorosilane, wherein the acryloxyalkyl dimethylchlorosilane is any one of claims 1 to 6, wherein the macromonomer or copolymer has a purity of at least about 99%. The macromolecular monomer or copolymer of claim 23, wherein the macromolecular monomer or copolymer contains less than about 0.1 wt.% of the methacrylate-functionalized hydrogenated derivative. The macromolecular monomer or copolymer of claim 23 or 24, wherein the macromolecular monomer or copolymer contains less than about 0.05 wt.% of the methacrylate-functionalized hydrogenated derivative. The macromolecular monomers or copolymers of claims 23 or 24 have a molecular weight of less than about 5,000 Daltons. The methacrylate functional macromonomers or copolymers derived from acryloxyalkyl dimethylchlorosilane, as claimed in claims 23 or 24, wherein the macromonomers or copolymers have a purity of at least about 99.3%.