Multifunctional Coupling Agents for Living Cationic Polymerization. 6. Synthesis of Multiarmed and End-Functionalized Poly ( α-methylstyrene) with Multifunctional Silyl Enol Ethers

Tri- and tetraarmed polymers ( 3-P and 4-P ) of α-methylstyrene (αMeSt) and their end-functionalized versions ( 12 ) [R 4 - m C{CH 2 OC 6 H 4 COCH 2 −(αMeSt) n −CHMeOCH 2 CH 2 −X} m (Me = CH 3 ); arm number m = 3 (R = Me), 4; X = Cl, OCOMe, OCOCMe=CH 2 ] have been synthesized by coupling reactions of living poly(αMeSt) with multifunctional silyl enol ethers [R 4 - m C{CH 2 OC 6 H 4 C(OSiMe 3 ) CH 2 } m; 3, m = 3, R = Me; 4, m = 4]. The living poly(αMeSt) was prepared by living cationic polymerization in methylene chloride solvent at −78 °C with the hydrogen chloride−vinyl ether adduct [Cl−CHMe(OCH 2 CH 2 −X)] as initiator in conjunction with tin tetrabromide (SnBr 4 ). Subsequently, the living chains were allowed to react with 3 or 4 in the presence of N -ethylpiperidine to give the target multiarmed polymers in high yield (>90%). Specifically for αMeSt, it proved crucial that N -ethylpiperidine and similar nucleophiles should be added into the living polymer solution for its efficient coupling to occur. In the end-functionalized polymers ( 12 ), each of the four poly(αMeSt) arms carries a terminal function X, which would provide a novel cross-linking agent [X = OH (from OCOMe)] or a tetraarmed macromonomer (X = methacryloyl).