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为止所认为的和理论上所描述的更丰富的现象。 根据流体动力学和扩散的时间尺度，相粗化的标度不变性可以打破和锯齿状域可以形成。 在初步的实验中，各种粘度制度的理论模拟中考虑的实验观察。 一个详细的定量比较理论和粘性流体，如聚合物熔体的相分离，将实验确定从高度不混溶到弱不相容的流体对。 主要的模型系统将是聚（甲基丙烯酸甲酯）/聚苯乙烯（PS），PS/溴化PS，PS/聚（乙烯基甲基醚）高于其玻璃化转变温度。 预计获得的数据超出本模拟的适用范围，最明显的是具有不对称组成和体积分数以及不对称粘度的流体。 二元粘性液体的一个有趣的扩展将是对其中一相中含有小颗粒或珠粒的系统的研究。 最近的理论表明，添加硬质颗粒显着改变相分离的动力学和形态。 为了产生真正的二维流体，将开发一种特殊的样品制备方法，将聚合物膜夹在Si 3 N4膜之间。 将对表面进行处理，使其对所用聚合物呈中性或接近中性。 在此过程中，控制约束效应，如在薄聚合物薄膜的粘度变化将实现。 近边X射线吸收精细结构（NEXAFS）显微镜将是一个重要的表征工具，由其他显微镜（AMF，VLM，SEM）补充。 - NEXAFS光谱的理论理解的改进将被追求。 成分定量的准确性将得到提高。学生将在执行位于物理，化学，材料和高分子科学的接口跨学科的研究项目进行培训。 将推进对聚合物薄膜的基本理解，这可能会改善诸如涂料，粘合剂，润滑剂，油墨和半导体工业中的各种薄膜应用等应用。 这项工作的一部分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.