Solvent effects on aggregation behavior of polyvinyl alcohol solutions
Solvent effects on aggregation behavior of polyvinyl alcohol solutions
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DOI：
10.1016/s0032-3861(01)00056-8
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发表时间：
2001-06-01
期刊：
影响因子：
4.6
通讯作者：
He, CH
中科院分区：
文献类型：
--
作者：
Hong, PD;Chou, CM;He, CH
研究了聚乙烯醇（PVA）溶液从稀溶液到半稀溶液的聚集行为，考察了溶剂质量和聚合物浓度对PVA聚集行为的影响。静态和动态光散射结果的结合表明，在稀溶液中的热力学驱动力主要支配PVA/N-甲基吡咯烷酮（PVA/NMP）溶液的动态行为。与PVA/水溶液相比，流体动力学相互作用将主导溶液的动力学行为。通过动态光散射测量研究了半稀溶液动力学行为的浓度依赖性。对于PVA/水溶液，快模的流体动力学关联长度具有浓度依赖性xi（D），= [eta ]C-0.42，其指数值与标度理论在边际溶剂中的预测值接近。另一方面，对于PVA/NMP溶液，指数值接近于在良溶剂极限下的标度理论的预测值：-0.75。然而，与预期相反，在相同的条件下，在PVA/NMP溶液中的凝胶化行为不能发生在PVA/水溶液中，即使水对PVA的亲和力远低于NMP。在这项工作中，我们认为PVA/NMP溶液可能具有能够形成均匀网络结构的特性。在PVA/NMP溶液中，当链开始重叠时，分子间缔合起主导作用。另一方面，结合DLS结果和我们以前的工作，PVA/NMP溶液的凝胶化被认为是由于在瞬态网络连接中形成复合物，即分子复合物的形成是在良溶剂体系中的物理凝胶化的关键。(C)2001爱思唯尔科技有限公司版权所有。
The present study elucidates the effects of solvent quality and polymer concentration on the aggregation behavior of polyvinyl alcohol (PVA) solutions from the dilute solution to semi-dilute solution regions. Combination of the results in static and dynamic light scattering indicates that in dilute solution the thermodynamic driving forces primarily dominate the dynamic behavior of PVA/N-methylpyrrolidone (PVA/NMP) solution. In contrast with PVA/water solution, the hydrodynamic interaction would dominate the dynamic behavior of the solution. The concentration dependence on the dynamic behavior of semi-dilute solution has also been studied through DLS measurement. For PVA/water solutions, the hydrodynamic correlation length of fast mode has a concentration dependence given by xi (D), = [eta ]C-0.42, and the value of exponent is close to the predicted value from scaling theory in the marginal solvent. On the other hand, for PVA/NMP solutions the value of exponent is close to the predicted value from the scaling theory in good solvent limit: -0.75. However, contrary to the expectation, the gelation behavior could not occur in PVA/water solutions at the same condition of gelation in PVA/NMP solution even though the affinity of water to PVA is much lower than that of NMP. In this work, we considered that the PVA/NMP solution might possess a character that could form a homogeneous network structure. The intermolecular associations must play a dominant role as soon as the chains start to overlap in PVA/NMP solution. On the other hand, combining the DLS result with our previous work, the gelation of PVA/NMP solutions is considered due to complex formation in the transient network junctions, i.e. the formation of molecular complex is crucial to the physical gelation in a good solvent system. (C) 2001 Elsevier Science Ltd. All rights reserved.