Semicrystalline Polymers under Confinement as Thin Films

薄膜几何结构中的结晶聚合物将使用电学和光学方法进行研究。我们将研究由薄膜几何形状引起的对分子迁移率的限制，并将其与在本体聚合物中观察到的行为进行比较。所选择的材料是具有良好表征的分子量和规整性的模型体系，包括全同立构聚苯乙烯(i-PS)和全同立构聚苯乙烯(a-PS)的可混溶共混物。膜厚对玻璃化转变和冷结晶动力学的影响将被确定为均聚物I-PS和共混物聚合物链的膜厚度和均方根端到端距离。在纳米级薄膜中，将使用光学方法测量取向层弛豫，并使用高温原子力显微镜进行表面研究，以证实介电实验。薄膜的非原位表征将包括用轮廓术测量厚度和用扫描电子显微镜分析表面结构。薄膜的结晶度将使用傅里叶变换红外光谱进行评估。在块状薄膜中，将同时进行广角和小角X射线散射，以评估结构参数，并根据散射强度的时间发展确定结晶动力学。差示扫描量热法及其温度调制方法将被用来测定较厚的薄膜的玻璃化转变温度和结晶度。%的聚合物薄膜在技术上的应用越来越频繁，因此了解可结晶的聚合物纳米级薄膜的结构和性能具有重要的实际意义。这项工作将为了解聚合物薄膜中的分子运动和结晶过程提供基础信息，这些过程直接影响到薄膜的材料性能和性能特性。

Crystallizable polymers in the thin film geometry will be studied using electrical and optical methods. Constraints on molecular mobility that arise from the thin film geometry will be investigated and compared to behavior observed in the bulk polymers. Materials chosen for the study are model systems having well-characterized molecular weights and tacticity, comprising isotactic polystyrene (i-PS), and miscible blends of isotactic with atactic polystyrene (a-PS). Effects of film thickness on the glass transition and cold-crystallization kinetics film thickness and root mean square end-to-end distance of the polymer chain will be determined for homopolymer i-PS and blends. In nanometer-scale thin films, optical methods measuring alignment layer relaxation, and surface studies using elevated temperature atomic force microscopy, will be used to corroborate the dielectric experiments. Ex-situ characterization of the films will include thickness measurement by profilometry, and surface structure analysis by scanning electron microscopy. Degree of crystallinity of thin films will be assessed using Fourier Transform infrared spectroscopy. In bulk-scale films, simultaneous wide and small angle X-ray scattering will be performed to assess structural parameters and to determine crystallization kinetics from the time development of scattered intensity. Differential scanning calorimetry and its temperature-modulated variant will be used to determine the glass transition temperature and degree of crystallinity of thicker films.%%%Thin polymer films are being used more frequently in technological applications, and it is therefore of great practical interest to understand the structure and properties of crystallizable polymer nanometer-scale films. This work will provide fundamental information about the molecular motions and crystallization processes in thin polymer films, which impact directly the material properties and performance characteristics of thin films.