| Summary: | 碩士 === 國立臺北科技大學 === 有機高分子研究所 === 92 === In this study, macromonomers of poly(L-lactide) were synthesized via cationic ring-opening polymerization with 2-hydroxyethyl methacrylate(HEMA) and stannous octoate was used as initiator and catalyst, respectively. These marcomonomers along with different molar ratios of acrylic acid monomers were initiated by 2, 2’-azobis(2-methyl propionitrile)(AIBN) to produce graft copolymers. Products were purified several times in order to obtain targeted copolymers.
1H NMR spectra were used to determine the mole fraction of poly(L-lactide) and poly(acrylic acid) in graft copolymers. In 125 MHz 13C NMR spectra of graft copolymers, it shows all signals of poly(L-lactide), poly(acrylic acid) and connecting HEMA. Comparing to the position of the resonance signals representing -O(CH2)2O- of HEMA in macromonomer and graft copolymer, significant downfield shift was observed, indicating the existence of graft copolymer. FTIR spectrum of graft copolymers shows characteristic vibration absorption of C-H, C=O and C-C stretching.
GPC were used to determine molecular weights of graft copolymers. It was found that molecular weights of graft copolymers are higher than those of starting macromonomers and increase following increase in mole fraction of the poly(acrylic acid). In DSC thermograms, graft copolymers exhibit two glass transition temperatures which belong to poly(L-lactide) and poly(acrylic acid), individually, and with increases of poly(acrylic acid) fractions in graft copolymers, the Tg of poly(acrylic acid) become lower. These graft copolymers were found to be amorphous.
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