Orientation Induced Crystallization in Multi-Component Melts Under Flow

技术总结：拟议的研究旨在研究流动条件下多组分聚合物熔体中取向诱导结晶前体结构的几种新发现的现象。 这些现象包括：（1）在纳米和宏观尺度上形成的前体结构，它们可以作为多尺度支架来引导结晶过程;以及（2）流动诱导的前体结构、流变行为、多组分相行为和流场类型之间的关系。为解决上述问题，本研究提出以下研究计画。 首先，所选择的全部基于聚烯烃的多组分体系将包括模型化合物（例如高分子量可结晶物质和低分子量非结晶物质）的聚合物共混物、链段烯烃嵌段共聚物（仅具有一个可结晶嵌段）和具有良好分散的表面改性的碳纳米纤维/纳米管的聚烯烃纳米复合材料。其次，为了理解流变行为，将通过基于GEX的模型描述动态和瞬态模式中的实验数据，以产生负责形成前体结构的弛豫机制。 第三，将通过使用包括流变学、原位同步小角X射线散射（SAXS）、广角X射线衍射（WAXD）和光散射技术的组合方法来跟踪真实的时间结构的发展。 最后，要了解不同的流场的效果，结果从简单的剪切（包含旋转元素）和拉伸流（没有旋转元素）将compared.NON-TECHNICAL摘要：流动诱导结晶的主题，特别是在多组分系统，如聚合物共混物，嵌段共聚物和纳米复合材料，仍然是当今聚合物科学和工程中最重要的问题之一。随着同步加速器X射线散射和衍射方法的可用性，以及流变学和光散射技术的耦合，现在可以适当地解决许多悬而未决的问题。众所周知，在聚合物加工操作期间由流动诱导的分子取向可以深刻地影响结晶动力学以及最终聚合物的形态和性质。在拟议的研究中获得的知识将显着提高我们的能力，以了解结构，相行为，过程和性能之间的关系，在多组分系统中含有结晶组分。 这些信息将导致改进的聚合物工艺和新的聚合物产品的开发，从而使聚合物工业和整个社会受益。 这一提议的广泛影响有几个方面。 直接的好处是，拟议的活动将在学术机构和政府机构之间建立密切的联系（即，斯托尼布鲁克大学，国家同步加速器光源）。学生和科学家将在这两个机构接受培训，并获得跨学科的研究经验。他们将接触到相关的工业问题，并将有机会与工业科学家直接互动来解决这些问题。 他们还将参与斯托尼布鲁克和布鲁克海文国家实验室的夏季研究计划，在那里他们将监督高中和本科生以及工业科学家进行同步加速器X射线实验和相关的实验室研究。

TECHNICAL SUMMARY:The proposed research aims to investigate several newly discovered phenomena of orientation-induced crystallization precursor structures in multi-component polymer melts under flow. The phenomena include (1) formation of precursor structures at both nanoscopic and macroscopic scales, which can act as multi-scaled scaffolds to guide the crystallization process, and (2) the relationships among the flow-induced precursor structures, rheological behavior, multi-component phase behavior and type of flow field. To tackle the proposed problems, following research plans have been composed. First, the chosen multi-component systems, all based on polyolefin will include polymer blends of model compounds (e.g. high molecular weight crystallizable species and low molecular weight non-crystallization species), segmental olefin block copolymers (with only one crystallizable block) and polyolefin nanocomposites with well dispersed surface-modified carbon nanofibers/nanotubes. Second, to understand the rheological behavior, experimental data in dynamic and transient modes will be described by a GEX-based model in order to yield relaxation mechanisms responsible for the formation of precursor structure. Third, the development of structure in real time will be following by the use of combined methods including rheology, in-situ synchrotron small-angle-X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD) and light scattering techniques. Finally, to understand the effect of different flow fields, results from simple shear (containing the rotational element) and extensional flow (without the rotational element) will be compared.NON-TECHNICAL SUMMARY:The subject of flow-induced crystallization, especially in multi-component systems such as polymer blends, block copolymers and nanocomposites, remains to be one of the most important problems in polymer science and engineering today. With the availability of synchrotron X-ray scattering and diffraction methods, and the coupling of rheology and light scattering techniques, many unanswered questions of fundamental importance can now be suitably addressed. It is known that molecular orientation induced by flow during polymer processing operations can deeply affect the crystallization kinetics as well as the final polymer morphology and properties. The knowledge obtained in the proposed study will significantly enhance our ability to understand the relationships between structure, phase behavior, process and property in multi-component systems containing crystalline components. The information will lead to developments of improved polymer processes and new polymer products, thus benefiting the polymer industry in specific and the society in general. The broader impacts of this proposal are several. The immediate benefit is that the proposed activities will produce tight links between academic and government institutions (i.e., Stony Brook University, National Synchrotron Light Source). Students and scientists will be trained in both institutions and receive interdisciplinary research experiences. They will be exposed to relevant industrial problems and will have a chance to tackle these problems with direct interactions from industrial scientists. They will also be involved in the Stony Brook and Brookhaven National Laboratory summer research programs, where they will supervise high school and undergraduate students as well as industrial scientists to carry out synchrotron X-ray experiments and related in-laboratory studies.