Synthesis and properties of microstructure-controlled ethylene-vinyl alcohol copolymers and their derivatives

Abstract

New side-chain liquid crystalline polymers with flexible spacer backbone were prepared by ring opening metathesis polymerization of cyclododecadiene derivative with tungsten-based catalyst systems. Prepared monomers were 4,8-cyclododecadienyl 4````-methoxybiphenyl terephthalate(CDDMBT), 4,8-cyclododecadienyl 4````-cyanobiphenyl terephthalate(CDDCBT), 4,8-cyclododecadienyl cholesteryl terephthalate (CDDCHOT), 4,8-cyclododecadienyl 4````-methoxyphenyl terephthalate (CDDMPT), and 4,8-cyclododecadienyl 4````-methoxybiphenyl carboxylate (CDDMBC). Double bonds in the polymer backbone were hydrogenated with $H_2$/Pd(C). The number average molecular weight of the polymer was $1.1 \times 10^4 \sim 1.5 \times 10^4$ relative to polystyrene standards as determined by GPC. The thermal properties of the monomers and the polymers were analyzed by differential scanning calorimetry(DSC), cross-polarized optical microscopy, and X-ray diffraction analysis. The monomers and polymers with 2-ring mesogenic group(CDDMPT and CDDMBC) showed no liquid crystallinity. On the other hand, 3- or more ring mesogenic system showed liquid crystallinity at their monomer and/or polymer. Particularly notable was that the liquid crystalline polymer exhibited much lower phase transition temperature than the monomer. 4,8-Cyclododecadienyl acetate (CDDA) and 4-cyclooctenyl acetate (COA) were prepared and polymerized. The number average molecular weight of the polymer was 10,500 ~ 23,000 and polydispersity Mw/Mn were 2.0 ~ 2.3 in 90 ~ 99 % conversion when Basset catalyst system used. The double bonds in the obtained polymer were hydrogenated by H2/Pd(C) or p-toluenesulfonyl hydrazide. Perfectly linear EVAL copolymers as a gas barrier film were prepared by ROMP of CDDA and COA followed by modification of hydrogenation and hydrolysis. Photo-alignment polymer with regular intervals between cinnamate groups were synthesized from linear EVAL copolymer by polymer reaction with cinnamoyl chloride.``