Sequence-Controlled Polymer Synthesis Derived from Alcohols, Cyclic Enol Ethers, and Vinyl Ethers: Selective Generation of 2-Alkoxy Cyclic Ethers Followed by Living Cationic Alternating Copolymerization by the One-Pot Process

Abstract

Syntheses of sequence-controlled copolymers with controllable molecular weights and chain ends composed of alcohols, cyclic enol ethers, and vinyl ethers (VEs) were demonstrated using an approach consisting of selective monomer generation and subsequent alternating copolymerization. Acid-catalyzed additions of alcohols to 2,3-dihydrofuran or 3,4-dihydro-2H-pyran proceeded quantitatively to yield 2-alkoxy cyclic ethers (2-ACEs). Subsequent cationic alternating copolymerization of the 2-ACE and a VE proceeded successfully via concurrent ring-opening and vinyl-addition mechanisms, yielding copolymers with periodically arranged alcohol-derived side chain-containing cyclic enol ether and VE moieties in the repeating units. Complete degradation of the obtained copolymers into a single compound by alcoholysis confirmed the alternating sequences. The use of 2-propanol, (−)-menthol, and (1R)-endo-(+)-fenchyl alcohol was effective for the syntheses of well-defined polymers, whereas the use of methanol resulted in oligomers. The bulkiness of the alkoxy groups of the 2-ACEs likely contributed to the preference for propagation rather than chain transfer.