Controlled polymerization and side reaction mechanism of bio-sourced pentanediamine-derived semi-aromatic copolyamides

Abstract

Controlled polymerization to improve molecular weight by controlling side reactions has always been a major challenge in the commercial preparation of polyamides with new chain structures. Traditionally, it has been assumed that the side reaction of decarboxylation makes increasing the molecular weight of polyamides difficult, whereas the side reaction of deamination causes cross-linking phenomena such as gel formation. In this work, a new perspective is revealed by studying the high-temperature solution prepolymerization – solid phase post-polycondensation based on pentanediamine, terephthalic acid and adipic acid, that is, the deamination reaction of the high-temperature cyclization of pentanediamine and the subsequent condensation reaction between piperidine (the deamination cyclization product) and an oligomer are the most critical reasons for the difficulty in the growth of the molecular weight for polyamide polymerization. The phase diagrams of reversible and non-reversible control reaction regions were obtained by analyzing the reaction kinetics of the prepolymerization parameter-reaction degree. As a result, bio-based polyamides with properties comparable to those of commercial high-temperature resistant polyamides were prepared. This work will provide strong theoretical support for the large-scale preparation of high-temperature resistant polyamides based on the bio-based monomer pentanediamine.