Synthesis of PVA having high molecular weight and high syndiotacticity, and its application as a functional material.

(1)研究了溶剂聚合对联苯二甲酸乙烯酯(VP)的聚合度和立构规律性的影响，以DMSO为溶剂，可以高转化率得到高相对分子质量(4×10~5)的PVP。降低溶剂的极性有增加PVA间规活性的趋势。通过分析侧基的堆积效应、库仑排斥效应和倒数第二效应，在-20ﾟ的正辛烷中可以得到高间规(68%，diad)的聚乙烯醇(PVA)。共等规构化参数可以被估算。用伯努利静力学和蒙特卡罗方法估算了聚乙酸乙烯酯中的序列分布。3)间规PVA(St-PVA)的物理力学性能不同于等规PVA(it-PVA)和商品化无规PVA(at-PVA)，因为它具有较强的分子间作用力；高相对分子质量的St-PVA由于难以有效的拉伸和有序化，很难形成有序的纤维结构。我们利用我们设计的微热区拉伸法成功地制备了高强度(2 Gpa)、高模数(80 Gpa)的PVA纤维。更重要的是。以St-PVA(Pn=1650，St%=61.3)为原料，采用冻融循环法制备了高定伸应力(0.47 Mpa)的PVA凝胶。从活性污泥中分离出来。商品PVA的降解结果使三元等规度从21%变为13%，表明PVA中的等规链序列更容易被生物降解。事实上。等规度高的PVA易降解，而St-PVA难降解。

(1) Solvent effects of solution polymerization on the degrees of polymerization and the stereoregularities for vinyl pivarate (VP) were studied.When using DMSO as a solvent, PVP with high molecular weight (4x10^5) could be obtained in high conversion. Decreasing polarity of the solvent tended to increase PVA syndiotacticities. PVA with high syndiotacticity (68%, diad) could be attained in n-octane at -20ﾟC.2) Tacticity and cotacticity simulations for poly (vinyl ester) homologs, which provide PVA with various stereoregularities, were succcessfully carried out using computer by analyzing stacking effect, Coulon repulsion effect and penultimate effect of the side groups. Co-isotactic parameters could be evaluated. Estimation of the sequence distribution in poly (vinyl acetate) was done using Bernoulli's statics and the Monte Carlo method. Results obtained were in good agreement with those by ^1H NMR spectrum for the polymer.3) Physical and mechanical properties of syndiotactic PVA (st-PVA) were distinct characteristically from those in isotactic PVA (it-PVA) and commercial atactic PVA (at-PVA) due to its strong intermolecular forces.Building up of ordered fiber structure of st-PVA with high MW was not easy because of difficulty of effective drawing and ordering.We succeeded in preparation of outstanding PVA fiber with high strength (2GPa) and high modulus (80GPa) using micro heat-zone drawing method designed by us. Furthermore. PVA gel with high modulus (0.47MPa) could be prepared from st-PVA (Pn=1650, st%=61.3) by freeze-melt cycling.(4) PVA was biodegraded using a bacterium (Psudomonas sp.) isolated from anactivated sludge. The results of the degradation of commercial PVA altered triad-isotacticity from 21% to 13% and suggested the isotactic sequences in PVA are susceptible to biodegradation preferentially. In fact. PVA with high isotacticity was found to be easily degraded, whereas, st-PVA was hard to degrade.