Pattern Formation in Polymer Solidification

结晶动力学一般由两种相互竞争的现象控制，一种是热力学驱动力，它迫使晶体/非晶体界面向前移动，另一种是熔合热和任何不溶组分从该界面流出的速率。在很多情况下，这种竞争导致界面呈现出复杂的模式。提出的工作的目的是发展一个实验基础和理论框架，通过这种模式形成的聚合物系统可以被理解。这项工作将针对聚合物共混物中的球状结晶和熔融纺丝纤维微观结构的发展。一个静态结晶的实验程序将进行。在这种情况下，将研究有约束的（通过温度梯度的强迫运动）和无约束的球晶样生长。在这两种情况下，微观结构参数将被测量并与模型预测进行比较。同样地，一项研究将通过温度梯度对定向聚合物纤维结晶的温度和结晶半径进行研究。这些将与由首席研究员开发的模型进行比较。预计这项工作也将扩展现有的聚合物模式发展理论。

The kinetics of crystallization are, in general, controlled by two competitive phenomena, the thermodynamic driving force, which forces the crystal/noncrystal interface forward, and the rate at which the heat of fusion and any unincorporable components can flow away from that interface. Over a wide range of conditions, this competition causes the interface to assume intricate patterns. The aim of the proposed work is to develop an experimental base and a theoretical framework by which such pattern formation in polymer systems can be understood. This work will be directed at spherulitic crystallization in polymer blends and at the development of microstructure in melt-spun fibers. An experimental program for quiescent crystallization will be carried out. In this, both constrained (by forced movement through a temperature gradient) and unconstrained spherulite-like growth will be studied. In both cases, microstructural parameters will be measured and compared to model predictions. Likewise, a study will be made of the temperature and crystallite radius of oriented polymer fibers crystallized by running them through a temperature gradient. These will be compared to those of a model developed by the principal investigator. It is expected that the work will also extend existing theory for pattern development in polymers.