ABSTRACT
With tetrahydrofuran as a solvent and pyridium p-toluenesulfonate as a catalyst, the hydroxyalkyl vinyl ethers 2-hydroxyethyl vinyl ether (2E), 4-hydroxybutyl vinyl ether (4B), and 6-hydroxyhexyl vinyl ether (6H) underwent step-growth self-polyaddition, generating polymers with an acetal main-chain structure. The molecular weight of the resulting polymers increased gradually during the initial polymerization period at room temperature. However, decomposition occurred after about 22–24 h, and the presence of a large amount of catalyst accelerated the latter process. The three monomers exhibited different polymerization capabilities. In contrast to the smooth polymerization of 6H, cyclization side reactions usually took place during the polymerizations of 4B and 2E, which resulted in low polymer yields and low molecular weights because of the formation of unreactive small cyclic acetals. In the self-polyaddition of 4B, this side reaction was greatly restricted at high concentrations of the monomer. Higher temperatures (60°C–70°C) remarkably accelerated the self-polyaddition process to produce polymers with high molecular weights. However, the polymerizations at high temperatures had to be terminated within about 2 h to avoid the severe decomposition of the polymers. Copolymers were also obtained via the copolyaddition of any two of the monomers. The easiness of the incorporation of the monomers into the copolymers was in the sequence 6H > 4B > 2E. Poly(6H), poly(4B), poly(2E), and the copolymers possessed different hydrophilicities and were stable in basic, neutral, and even weak acidic media but exhibited degradation in the presence of a strong acid.
