ALDOL-GTP in Controlled Synthesis of Vinyl Alcohol Polymers

Abstract

Sequential silyl aldol condensation involving aldehydes and silyl vinyl ethers gives monodisperse poly(silyl vinyl ether) whose molecular weight (${\overline {\text{M}} _{n\,}}$1000-160,000) is controlled by the aldehyde initiator. The new process, termed aldol-group transfer polymerization (aldol-GTP) involves a silyl group transfer from monomer to the carbonyl oxygen of either the initiator or the living polymer, leading to generation of a new terminal aldehyde functional group. The reaction is catalyzed by Lewis acids and can be initiated by other electrophiles, e.g., alkyl halides and acetals. The living polymers are stable, neutral materials whose hydrolytic stability depends on the bulkiness of the sily group. In general, aromatic aldehydes tend to react more cleanly as initiators than do aliphatic aldehydes. Unlike the GTP of methyl methacrylate in which the silyl group is transferred from the initiator to the monomer, aldol-GTP involves a transfer of silyl group from monomer to initiator. Some of the advantages of aldol-GTP over existing methods such as cationic polymerization include operability over a broad temperature range, complete monomer conversion, living polymer formation, very good molecular weight control, and facile block copolymer synthesis. It permits control of hydrophilicity of block copolymers.