Synthesis and Characterization of New Biodegradable Amphiphilic Poly(ethylene oxide)-b-poly[(R)-3-hydroxy butyrate]-b-poly(ethylene oxide) Triblock Copolymers

Abstract

New biodegradable amphiphilic ABA triblock copolymers consisting of poly(ethylene oxide) (PEO) as the hydrophilic block and poly[(R)-3-hydroxy butyrate] (PHB) as the hydrophobic block were synthesized by coupling two chains of methoxy-PEO-monocarboxylic acid with a low molecular weight telechelic hydroxylated PHB (PHB-diol) chain in the middle. The PHB-diol was prepared from high molecular weight natural source PHB by transesterification reaction with diethylene glycol. The target triblock copolymers were isolated and purified from the reaction mixtures through repeated precipitation and fractionation. The structures and molecular characteristics of the PEO−PHB−PEO triblock copolymers were studied by GPC, 1H NMR, and FT-IR. All of the triblock copolymers had unimodal peaks in the GPC chromatographs. The chain architecture of the triblock copolymers was confirmed by the 1H NMR spectra. A combination of GPC and 1H NMR analysis determined the lengths of the PEO and PHB blocks of the copolymers. The thermal p...