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

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(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.