Copolymerization of β‐Butyrolactones into Functionalized Polyhydroxyalkanoates Using Aluminum Catalysts: Influence of the Initiator in the Ring‐Opening Polymerization Mechanism

Abstract

Within bioplastics, natural poly(3‐hydroxybutyrate) (PHB) stands out as fully biocompatible and biodegradable, even in marine environments; however, its high isotacticity and crystallinity limits its mechanical properties and hence its applications. PHB can also be synthesized with different tacticities via a catalytic ring‐opening polymerization (ROP) of β‐butyrolactone (BBL), paving the way to PHB with better thermomechanical and processability properties. In this work, we extend our catalyst family based on aluminum phenoxy‐imine methyl catalyst [AlMeL2], that revealed efficient in the ROP of BBL, to the halogeno analogous complex [AlClL2]. As well, we further explore the impact on the ROP mechanism of different initiators with a particular focus in dimethylaminopyridine (DMAP), a hardly studied initiator for the ROP of BBL. A thorough mechanistic study was performed that evidences the presence of two concomitant DMAP‐mediated mechanisms, that lead to either a DMAP or a crotonate end‐capping group. Besides, in order to increase the possibilities of PHB post‐polymerization functionalization, we explore the introduction of a side chain functionality, establishing the copolymerization of BBL with β‐allyloxymethylene propiolactone (BPLOAll), resulting in well‐defined P(BBL‐co‐BPLOAll) copolymers.This article is protected by copyright. All rights reserved