Complete depolymerization of poly(ester-alt-thioether)s under mild conditions into AB functional monomers

Abstract

The chemical recyclability of poly(ester-alt-thioether) structures is investigated. Different polymers were synthesized by alternating anionic ring-opening copolymerization of thiolactone and epoxide monomers using benzyl alcohol – BEMP phosphazene base as initiating system. Controlled structures with number-average molar masses between 2000 and 5000 g mol⁻¹ were obtained. In a second time, degradation studies were carried out by methanolysis in acidic and basic conditions. The influences of the base/acid concentration and of the epoxide unit lateral substituent on the degradation rate were also investigated. The structure of degradation product has been confirmed by ¹H, ¹³C NMR, SEC and ESI mass spectrometry, and corresponds to α-hydroxy-ω-methyl ester repeating unit molecules. These molecules were subsequently used as A–B monomers in step-growth polymerization syntheses using either p-toluene sulfonic acid (PTSA) or titaniumbutoxide (Ti(OBu)₄) as catalyst. The resulting condensation polymers were analyzed by NMR, SEC, MALDI ToF, TGA and DSC. Identical structures, comparable molar masses and slightly higher glass transition temperatures have been obtained compared to the ones of the native polymers synthesized by AROP.