高分子量アタクチックおよびシンジオタクチックポリ（ビニルアルコール）物理ゲルの力学強度と架橋サイズ

摘要

高重合度（N）およびシンジオタクチシティー（S-diad）の異なるポリ（ビニルアルコール）（PVA）を合成して物理ゲルを作り，MやS-diadがゲルの架橋長やヤング率に及ぼす影響を実験的に調べた．架橋長は田中-Stocknayerの式から推算した．ゲルの力学物性は，引張試験および圧縮試験よりS-Sカーブを作成し，ヤング率Eを求めて評価した．その結果，ゲルの架橋長ζは，重合度N＜10~4では単調に増大したが，N＞10~4になるとほぼ一定の値を示した．また，S-diadが高い試料ほどぐは人きくなった．さらに，ゲルのヤング率Eも架橋長与が増大すると増大する傾向を示した．このことから，架橋長ζの大きさが力学物性に影響を与えていることが示唆された．%It is well known that poly (vinyl alcohol) (PVA) in the mixed solvent of dimethysulphoxide (DMSO) and water converts to a thermoreversible gel with a phase transition near room temperature. In this study, syndiotactic-rich PVA samples with high-molecular weight (degree of polymerization N between 4600 and 23600) were synthesized. The thermal stability of PVA gels was evaluated from their gel-melting temperature, and the Young's modulus E was determined by tensile test and compression test. From there, junction size was estimated as a function of N. The junction length ζ in number of vinyl alcohol units and multiplicity S in number of PVA chains were estimated from the Tanaka-Stockmayer theory (TS theory). Gel-melting temperatures of syndiotactic-PVA gels were higher than those of atactic-PVA gels. The PVA junction point was found to be crystalline and its length ζ increased slowly with increasing N for N < 10~4, above which it showed a plateau region. Both Young's modulus E and junction size ζ × S increased with increasing degree of polymerization N and number of syndiotactic-diads.