Polymer Dissolution

聚合物溶解

• 批准号: 9212482
• 负责人: Nicholas Peppas
• 金额: $ 21.71万
• 依托单位: Purdue Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-15 至 1996-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9212482&HistoricalAwards=false
• 关键词: Polymer; Dissolution

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.

玻璃状聚合物的溶解可以被认为是具有案例 II 传输特征的溶剂渗透和由聚合物解缠结控制的聚合物溶解的组合。 在目前的工作中，开发了用于溶剂渗透的异常传输模型，并与聚合物溶解的解缠结模型相结合。 溶剂渗透由聚合物的松弛或变形控制，并且扩散德博拉数被证明是主要的模型参数。 在解缠结模型中，聚合物分子的溶解需要溶剂浓度大于临界凝胶浓度，并且聚合物分子需要一定的时间来完成从凝胶态到液态的扩散运动的解缠结。 假定该时间等于信誉时间，其是分子量、溶剂浓度和链刚性的函数。 引入解缠结时钟的概念作为控制溶解的物质时钟。 新模型可以解释许多实验观察结果，例如溶剂和聚合物类型对溶解速率和凝胶层厚度的影响。 使用干涉测量法和临界角照明显微镜，对各种溶剂中的聚苯乙烯和聚甲基丙烯酸甲酯样品进行了实验研究。 使用椭圆光度法测量溶剂浓度分布和溶解速率。 通过脉冲梯度自旋回波核磁共振波谱测量聚合物必要的自扩散系数。 此外，还使用聚丙烯酸和聚乙烯醇在水中进行实验研究，以研究离子条件对溶解的影响。