Tandem polymerization consisting of cyclotrimerization and the Tishchenko reaction: synthesis of acid- and alkali-degradable polymers with cyclic acetal and ester structures in the main chain

Abstract

Tandem polymerization consisting of cyclotrimerization and the Tishchenko reaction of vinyl ethers and dialdehydes was demonstrated to proceed with the catalyst mixture of EtAlCl₂ and Al(OiPr)₃. The polymerization of 2-chloroethyl vinyl ether (CEVE) with isophthalaldehyde (IPA) or terephthalaldehyde (TPA) under the optimized conditions yielded polymers with a M_w of 3.5 or 6.7 × 10³, respectively, bearing cyclic acetal and ester structures in the main chain. The initial molar ratio of the catalyst mixture was highly responsible for the frequency of cyclotrimerization and the Tishchenko reaction, which generated the cyclic acetal and ester structures, respectively. Poly(CEVE-co-TPA) had a higher molecular weight than poly(CEVE-co-IPA) likely because of the decrease in cyclic oligomers. Moreover, the cyclic acetal and ester structures in the backbone were selectively hydrolyzed under acidic and alkaline conditions, respectively. In addition, three-component tandem polymerization with diethyl fumarate (DEF) as a third component also successfully proceeded by a transesterification reaction between DEF and an Al-bonded alkoxy group in addition to cyclotrimerization and the Tishchenko reaction, which resulted in a polymer consisting of cyclic acetal and two different ester structures in the main chain.