Design of -Benzyl Vinyl Ethers toward the Synthesis of Alternating Copolymers Composed of Vinyl Alcohol and Vinyl Ether Units.

In this work, we designed benzyl vinyl ethers carrying alkyl substituents at the benzyl position (i.e., -BnVEs) as bulky, reactive, and transformable monomers to realize the alternating cationic copolymerization with an alkyl vinyl ether (VE). In particular, the isopropyl substitution caused not only the bulkiness to suppress the successive propagation but also an enhancement of the vinyl group reactivity to promote crossover propagation with a less bulky VE comonomer. The isopropyl-substituted BnVE (Pr-BnVE) underwent living cationic alternating copolymerization with -butyl VE (BVE), and the alternating propagation was strongly suggested by the reactivity ratios. The subsequent deprotection of the -benzyl pendant afforded the vinyl alcohol (VA)-BVE alternating copolymer, and the corresponding statistical copolymer was also synthesized by using the nonsubstituted monomer (BnVE) instead of Pr-BnVE. The alternating copolymer exhibited a higher glass transition temperature, which likely stems from the uniform and efficient hydrogen-bonding formation due to the periodic sequence.