Miscibility and orientation behavior of poly(vinyl alcohol) / poly(vinyl pyrrolidone) blends
Miscibility and orientation behavior of poly(vinyl alcohol) / poly(vinyl pyrrolidone) blends
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聚（乙烯醇）/聚（乙烯基吡咯烷酮）共混物的混溶性和取向行为
DOI：
10.1002/polb.1990.090280308
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Toshisada Takahashi
中科院分区：
文献类型：
--
作者：
Y. Nishio;Tatsuo Haratani;Toshisada Takahashi
通过差示扫描量热法 (DSC) 和广角 X 射线衍射 (WAXD) 研究了聚乙烯醇/聚乙烯吡咯烷酮 (PVA/PVP) 共混物的混溶性。还通过 WAXD 和双折射测量检查了共混物单轴拉伸引起的分子取向。 DSC 热分析表明，聚合物对是可混溶的，因为在每种组合物中，单一玻璃化转变温度 (Tg) 位于两种均聚物的 Tg 之间。 Tg 与组成的曲线并不遵循单调函数，而是在 PVP 体积分数略低于 0.7 处呈现出尖点，正如 Kovacs 理论预测的情况一样。观察到 PVA 组分熔点的系统降低表明两种聚合物之间存在特定的分子间相互作用。聚合物-聚合物相互作用参数的负值 χ12 = 0.35（513 K 时）是通过使用在不同温度下等温结晶的样品进行对照实验的热力学方法估计的。与给定的拉伸比相比，拉伸共混物的光学双折射程度 (Δn) 随着 PVP 含量增加至 80 wt% 而急剧下降，最终发现在略高于 80 wt% 的临界 PVP 浓度下，Δn 从正值变为负值。对分子取向行为的讨论考虑了由于取向 PVA 和 PVP 分别产生的正向和负向贡献而导致的可混溶非晶相中的双折射补偿效应。
The miscibility of poly(viny1 alcohol)/poly(vinyl pyrrolidone) (PVA/PVP) blends is investigated by differential scanning calorimetry (DSC) and wide-angle x-ray diffraction (WAXD). The molecular orientation induced by uniaxial stretching of the blends is also examined by WAXD and birefringence measurements. It is shown by the DSC thermal analysis that the polymer pair is miscible, since a single glass transition temperature (Tg) is situated between the Tgs of the two homopolymers at every composition. The Tg versus composition curve does not follow a monotonic function but exhibits a cusp point at a PVP volume fraction of a little under 0.7, as in a case predicted by Kovacs' theory. The presence of a specific intermolecular interaction between the two polymers is suggested by an observed systematic depression in the melting point of the PVA component. A negative value of the polymer-polymer interaction parameter, χ12 = 0.35 (at 513 K), is estimated from a thermodynamic approach via a control experiment using samples crystallized isothermally at various temperatures. The extent of optical birefringence (Δn) of the drawn blends decreases drastically with increasing PVP content up to 80 wt %, when compared at a given draw ratio, and ultimately Δn is found to change from positive to negative at a critical PVP concentration of a little over 80 wt %. Discussion of the molecular orientation behavior takes into consideration a birefringence compensation effect in the miscible amorphous phase due to positive and negative contributions of oriented PVA and PVP, respectively.