Radiation-Induced Graft Copolymerization of Metacrylic Acid and Butyl Methacrylate onto Poly(3-hydroxybutyrate)

Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable thermoplastic polyester obtained microbiologically. Its main drawbacks are its thermal instability, brittleness, and moderate hydrophobicity, which limit its applications. The present study involves the chemical modification of PHB by means of the synthesis and characterization of graft copolymers with two selected monomers. Typical monomers, methacrylic acid (MA) and butyl methacrylate (BuM), were graft polymerized onto PHB by radiation-induced graft copolymerization reaction to improve PHB's hydrophilicity. The effect of different solvents on the radiation-induced graft copolymerization of the monomers onto poly(3-hydroxybutyrate) was investigated. Structures of the graft copolymers obtained were determined by Fourier transform-infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Examination of the infrared spectra of the polymeric materials showed that there are no significant changes in their spectra apart from slight changes in the intensities of absorption bands. The results are consistent with the successful grafting of MA and BuM monomer onto PHB. Double melting peaks for grafted PHB were observed, which was probably caused by recrystallization of the graft copolymer. For grafted PHB, the introduction of MA and BuM groups hinders its crystallization, causing a decrease in the degree of crystallinity. The swelling behavior was also studied. The results showed that water uptake significantly increased. Hence, such a grafting process improved the hydrophilic character of PHB. The possibility of using these grafted polymers in practical biomedical applications is promising.