피발산비닐의 테트라히드로푸란계 저온용액중합에 의한 저분자량 교대배열 폴리비닐알코올 마이크로피브릴의 제조

Preparation of Low Molecular Weight Syndiotactic Poly(vinyl alcohol) Microfibrils Using Low Temperature Solution Polymerization of Vinyl Pivalate in Tetrahydrofuran

To prepare water-soluble syndiotactic poly(vinyl alcohol) (PVA) for various biomedical applications, low molecular weight syndiotactic PVA was synthesized by solution polymerization of vinyl pivalate (VPi) in tetrahydrofuran (THF) at a low temperature of 25℃ using 2,2'-azobis(2,4-dimethylvaleronitrile) (ADMVN) as an initiator and successive saponification of the poly(vinyl pivalate) (PVPi). The polymerization rate of VPi in THF was proportional to the 0.91 powers of ADMVN concentration, indicating the heterogeneous nature of polymerization. Syndiotactic diad content and number-average degree of polymerization ($P_{n}$) of PVA prepared were 60∼63% and 500-900, respectively. ($P_{n}$)s of PVPi and corresponding PVA increased as polymerization temperature and initiator concentration decreased. Syndiotacticity and molecular weight of PVA was greatly affected by polymerization temperature and THF concentration. A notable result was that despite of low molecular weight of the polymer, it exhibited crystalline microfibrillar morphology due to the high level of syndiotacticity.