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

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 <italic>rac</italic>‐β‐butyrolactone (BBL), paving the way to PHB with better thermomechanical and processability properties. In this work, the catalyst family is extended based on aluminum phenoxy‐imine methyl catalyst [AlMeL2], that reveals efficient in the ROP of BBL, to the halogeno analogous complex [AlClL2]. As well, the impact on the ROP mechanism of different initiators is further explored with a particular focus in dimethylaminopyridine (DMAP), a hardly studied initiator for the ROP of BBL. A thorough mechanistic study is 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, the introduction of a side‐chain functionality is explored, establishing the copolymerization of BBL with β‐allyloxymethylene propiolactone (BPLOAll), resulting in well‐defined P(BBL‐<italic>co</italic>‐BPLOAll) copolymers. [ABSTRACT FROM AUTHOR]