Synthesis and characterization of novel triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(-benzyl -glutamate)s as outer blocks

Abstract

BACKGROUND: Bioactive and biodegradable polyurethanes (BDPUs) have drawn much attention in recent years. As part of the research program to search for novel prepolymers for BDPUs, a study was carried out on the synthesis and characterization of triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(?-benzyl L-glutamate)s as outer blocks. RESULTS: A new macroinitiator terminated with phenylalanine was first prepared from the condensation of a distal hydroxy poly(tetrahydrofuran) with N-tert-butoxycarbonyl L-phenylalanine in the presence of dicyclohexylcarbodiimide, followed by removing the protecting group. Then, it was employed to initiate the ring-opening polymerization of ?-benzyl L-glutamate N-carboxyanhydride in varying feeding ratios to give rise to the targeted triblock copolymers. CONCLUSIONS: The length of the outer poly(?-benzyl L-glutamate) blocks was well tailored by varying the monomers to macroinitiator feeding ratio. All the triblock copolymers exhibited a nearly symmetrical and unimodal molecular weight distribution while only one distinct glass transition temperature was evidenced from -10°C to 25°C.

Keywords

γ-benzyl L-glutamate N-carboxyanhydride (BLG-NCA), phenylalanine end-capped macroinitiator, poly(tetrahydrofuran) (PTHF), ring-opening polymerization (ROP), triblock polypeptide copolymer