Syntheses of amphiphilic block copolymers. Block copolymers of methacrylic acid and p-N,N-dimethylaminostyrene

Amphiphilic block copolymers consisting of methacrylic acid (MA) sequences and p-N,N-dimethylaminostyrene (DMS) sequences were prepared by living anionic polymerization. DMS was polymerized by lithium naphthalene in tetrahydrofuran to yield a living polymer solution, to which trimethylsilyl methacrylate (TMSM) was added to allow the block copolymerization. The conversion of TMSM was dependent on the countercation, i.e., with Na⁺ as counterion, no quantitative conversion was reached owing to premature termination, whereas with Li⁺ the conversion was quantitative. The role of the counterion was discussed in some detail in connection with self-termination by the backbiting mechanism. The trimethylsilyl ester groups in the block copolymer were quantitatively hydrolyzed by treatment with aqueous methanol at room temperature, yielding MA sequences. The block copolymer of MA and DMS exhibited micellar properties in an aqueous solution.