Tetrabutylammonium → Methacrylic Acid

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To a solution of 22.6 g (26.2 mL, 130 mmol) of 1-methoxy-1-trimethylsiloxy-2-methyl-1-propene and 0.1 mL of tetrabutylammonium biacetate (0.1 M in propylene carbonate) in 300 mL of THF was added dropwise 268 g (304 mL, 1.69 mole) of trimethylsilyl methacrylate. During the course of the addition the temperature of the reaction mixture rose slowly to 50° C. To increase the rate of polymerization, an additional 1.5 mL of tetrabutylammonium biacetate (0.1 M in propylene carbonate) was added in 7 portions. After all of the monomer had been added, the temperature began to fall, and the solution was cooled with a bath to 30° C. The addition of 248 g (245 mL, 1.3 mole) of 2-phenylethyl methacrylate (purified by passage over a column of basic alumina under argon) was begun. An additional 0.6 mL of tetrabutylammonium biacetate (0.1 M in propylene carbonate) was added. During the addition the temperature rose 48° C. When the addition was complete and the temperature began to fall, the solution was cooled to 31° C., 0.15 mL of tetrabutylammonium biacetate (0.1 M in propylene carbonate) was added, and 128 g (128 mL, 0.52 mole) of ethoxytriethylene glycol methacrylate (purified by passage over a column of basic alumina under argon) was added dropwise from an addition funnel. Since little temperature change was observed, an additional 0.15 mL of tetrabutylammonium biacetate (0.1 M in propylene carbonate) was added to insure completion of the polymerization. Analysis of an aliquot of the solution by 1H nmr showed that there was no residual monomer present. To the solution of poly(trimethylsilyl methacrylate [48 mol %]-b-2-phenylethyl methacrylate [37 mol %]-b-ethoxytriethylene glycol methacrylate [15 mol %]) was added 350 mL of 0.03 M tetrabutylammonium fluoride trihydrate in methanol. The resulting mixture was refluxed for 16 hr and evaporated in a rotary evaporator under reduced pressure. The residual polymer was dried for 48 hr in a vacuum oven to give 515 g of poly(methacrylic acid [48 mol %]-b-2-phenylethyl methacrylate [37 mol %]-b-ethoxytriethylene glycol methacrylate [15 mol %]). 1NMR analysis of the product showed that no trimethylsilyl ester groups remained.

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