Polymer Dissolution

玻璃状聚合物的溶解可以被认为是一种 溶剂渗透的组合，具有情况II输送 和通过聚合物解缠结控制的聚合物溶解。 本文建立了一个反常输运模型 用于溶剂渗透，并与解缠结结合 聚合物溶解模型。 溶剂渗透是 由聚合物的松弛或变形控制， 扩散Deborah数被证明是一个主要模型 参数. 在解缠结模型中， 聚合物分子要求溶剂浓度 大于临界凝胶浓度， 分子被允许一定的时间来完成 扩散运动从凝胶状态到 液态 假设该时间等于 信誉时间，它是分子量的函数， 溶剂浓度和链刚性。 的概念 引入解缠时钟作为物质时钟 控制溶解。 新模型可以解释许多 实验观察，如溶剂类型的影响 和聚合物对溶解速率和凝胶厚度的影响 层. 实验研究是用良好的- 聚苯乙烯和聚（甲基）苯乙烯的特征样品 甲基丙烯酸酯）在各种溶剂中使用干涉测量法， 临界角照明显微术 溶剂 测量浓度曲线和溶出速率 使用椭圆偏振法。 必要的自扩散系数 通过脉冲梯度自旋回波NMR测量聚合物的 谱 此外，还进行了实验研究 在水中使用聚（丙烯酸）和聚（乙烯醇）， 研究离子条件对溶解的影响。

Dissolution of glassy polymers can be considered as a combination of solvent penetration featuring Case II transport and polymer dissolution controlled by polymer disentanglement. In the present work, an anomalous transport model is developed for solvent penetration and is coupled with a disentanglement model for polymer dissolution. Solvent penetration is controlled by the relaxation or deformation of polymer and the diffusional Deborah number is shown to be a major model parameter. In the disentanglement model, dissolution of polymer molecules requires that solvent concentration be greater than a critical gel concentration and that a polymer molecule be allowed a certain time to complete the disentanglement of diffusion movement from the gel state to liquid state. This time is assumed to be equivalent to the reputation time, which is a function of molecular weight, solvent concentration and chain rigidity. A concept of disentanglement clock is introduced as the material time clock controlling the dissolution. The new model may explain many experimental observations, such as effects of type of solvent and polymer on dissolution rate and the thickness of the gel layer. Experimental studies are performed with well- characterized samples of polystyrene and poly(methyl methacrylate) in various solvents using interferometry and critical angle illumination microscopy. The solvent concentration profiles and dissolution rates are measured using ellipsometry. The necessary self-diffusion coefficient of the polymer is measured by pulsed gradient spin echo NMR spectroscopy. In addition, experimental studies are performed using poly(acrylic acid) and poly(vinyl alcohol) in water to study the influence of ionic conditions on dissolution.