Radiation-Induced Graft Polymerization of Poly(3-Hydroxybutyrate) and Its Copolymer

Abstract

Abstract Graft copolymerization of methyl methacrylate (MMA) or 2-hydroxyethyl methacrylate (HEMA) onto poly(3-hydroxybutyrate) (PHB) and its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) {P(HBHV)} was carried out by using simultaneous radiation and preirradiation techniques from a 60Co γ-rays source. Degree of grafting (X g) of MMA onto both polymers increased as the irradiation dose increased. The X g for PHB graft-polymerized by simultaneous radiation was lower than that for the copolymer of 24 mol% HV content (24 M sample). On the contrary, X g of PHB graft-polymerized after preirradiation was higher than that of the 24 M sample. The X g depended on differences in regularity in the crystalline regions or crystallinity and rate of radical decay. Crystalline regions of PHB remained almost unchanged after grafting, while crystalline regions of the 24 M sample were partially destroyed by the introduction of grafting. Glass transition temperatures of both grafted polymers increased up to 8°C. The ...