Viscous Fluid Dynamics and Characterization of Nano-Structured Polymers

过去几年的理论工作表明，二维粘性流体的动力学是一种比迄今所认为和理论上描述的更为丰富的现象。随着水动力和扩散时间尺度的变化，相粗化的尺度不变性会被打破，形成锯齿状区域。在初步实验中，理论模拟中考虑的各种粘度状态已经在实验中观察到。将与理论进行详细的定量比较，并对粘性流体（如聚合物熔体）的相分离进行实验，确定从高度不混溶到弱不相容的流体对。主要模型体系将是高于玻璃化转变温度的聚（甲基丙烯酸甲酯）/聚苯乙烯（PS）， PS/溴化PS和PS/聚（乙烯基甲基醚）。预计获得的数据将超出当前模拟的适用范围，特别是具有不对称成分和体积分数以及不对称粘度的流体。对二元粘性液体的一个有趣的扩展将是在其中一个相中包含小颗粒或小珠的系统的研究。最近的理论表明，硬颗粒的加入显著地改变了相分离的动力学和形貌。为了生成真正的二维流体，将开发一种特殊的样品制备方法，将聚合物薄膜夹在Si3N4膜之间。表面将被处理，使其中性或接近中性的聚合物所利用。在此过程中，将实现对约束效应的控制，如聚合物薄膜粘度的变化。近边缘x射线吸收精细结构（NEXAFS）显微镜将成为重要的表征工具，其他显微镜（AMF， VLM， SEM）也将成为补充。-将继续改进对NEXAFS光谱的理论认识。提高了成分定量的准确性。学生将在物理，化学，材料和高分子科学的界面上进行跨学科研究项目的培训。对聚合物薄膜的基本理解将会提高，这可能会改善涂料、粘合剂、润滑剂、油墨和半导体工业中各种薄膜的应用。其中一部分工作是继续与陶氏化学公司的长期合作。

Theoretical work over the last years has shown that the dynamics of two-dimensional viscous fluids is a richer phenomenon than hitherto believed and described theoretically. Depending on the hydrodynamic and diffusive time scales, the scaling invariance of phase coarsening can break down and jagged domains can form. In preliminary experiments, the various viscosity regimes considered in the theoretical simulations have been experimentally observed. A detailed quantitative comparison to theory will be made and the phase separation of viscous fluids, such as polymer melts, will be experimentally determined for fluid pairs ranging from highly immiscible to weakly incompatible. The primary model systems will be poly(methylmethacrylate)/polystyrene (PS), PS/brominated PS, and PS/poly(vinyl methyl ether) above their glass transition temperature. It is expected that data is acquired outside the applicability of the present simulations, most notably fluids with asymmetric composition and volume fractions as well as asymmetric viscosities. An interesting extension to binary viscous liquids will be the investigation of systems that contain small particles or beads in one of the phases. Recent theory shows that the addition of hard particles significantly changes both the kinetics and the morphology of the phase separation. In order to generate truly two-dimensional fluids, a special sample preparation method that will sandwich the polymer films between Si3N4 membranes will be developed. The surfaces will be treated to make them neutral or near neutral for the polymers utilized. In the process, control over confinement effects such as changes of viscosity in thin polymer films will be achieved. Near Edge X-ray Absorption Fine Structure (NEXAFS) microscopy will be an important characterization tool, complemented by other microscopies (AMF, VLM, SEM). - Improvements in the theoretical understanding of NEXAFS spectra will be pursued. The accuracy of compositional quantitation will be improved.Students will be trained in executing interdisciplinary research projects situated at the interface of Physics, Chemistry, Materials and Polymer Science. Fundamental understanding of polymer thin films will be advanced, which might improve applications such as coating, adhesives, lubricants, inks and a variety of thin films applications in the semiconductor industry. Part of the effort continues a longstanding collaboration with Dow Chemical.