Metal catalyzed ring-opening polymerization of benzyl malolactonate: a synthetic access to copolymers of β-benzyl malolactonate and trimethylene carbonate

Abstract

The “immortal” coordination–insertion ring-opening polymerization of benzyl malolactonate (MLABe) initiated by the two-component catalyst system based on the zinc amide precursor, (BDI)Zn[N(SiMe₃)₂] (BDI = β-diiminate ligand), and benzyl alcohol (BnOH) acting as a co-initiator and a chain transfer agent proceeds in bulk at 40 °C. Functional telechelic poly(β-benzyl malolactonate)s, H-PMLABe-OBn, are thus obtained. Sequential copolymerization with trimethylene carbonate (TMC) affords block copolymers, PTMC-b-PMLABe, which are alternatively prepared from the chemical coupling of the PMLABe-COOH and PTMC-OH homopolymers. Simultaneous copolymerization of both the lactone and the carbonate monomers offers the PTMC-co-PMLABe random copolymers. The (co)polymers have been characterized by NMR, FT-IR, SEC and DSC analyses. These represent the first examples of β-benzyl malolactonate/carbonate copolymers. More importantly, these (co)polymers could be synthesized free of metallic residues thereby making them suitable as biomedical and pharmaceutical biomaterials.