Degradation of poly(conjugated ester)s using a conjugate substitution reaction with various amines and amino acids in aqueous media

We previously reported the quantitative main-chain scission reaction of polymers by a conjugate substitution reaction in aqueous ammonia, although the detailed behavior of the reaction was not analyzed. Herein, the degradation of a poly(conjugated ester), prepared from 1,4-butylene bis[α-(bromomethyl)acrylate] and fluorescein, with aqueous solution of various nucleophiles was investigated. Direct observation using UV‒vis spectrometry was effective for the analysis at the earliest stage of degradation, while size-exclusion chromatography was used for long-term degradation. The main-chain scissions were observed by a conjugate substitution reaction with ammonia, n-propylamine, diethylamine and α-amino acids, while similar degradation was observed with sodium acetate and water in the presence of triethylamine as a catalyst. The nucleophilicity of the nucleophiles and their affinity for the polymer affected the reaction rates in the earliest stage. On the other hand, to achieve complete chain scission, ammonia was most effective, probably because the dissolution of the degradation products led to the exposure of new polymer surfaces.