Dynamics of Polymer Mixtures: Intermolecular Coupling and Crystallizability

技术总结：先前在NSF-DMR支持下进行的关于缔合聚合物共混物和溶液的链段和局部动力学的研究集中在组成、分子间氢键强度和固有组分迁移率差异的作用上。这项研究主要是利用介电谱，利用其超宽的频率范围和高灵敏度。这项早期的工作引发了一些基本问题，这些问题将通过拟议的研究得到回答。例如，当聚合物组分的自缔合最小化时，强分子间耦合对链段动力学的作用是什么？在什么长度尺度上，音段动力学从同质性特征过渡到异质性特征？拟议的工作的第二部分旨在建立一个新的快速过程中观察到的混溶共混物的介电谱的起源。在这一部分的研究中要解决的原则问题包括：组分聚合物的结晶性在确定弱缔合聚合物之间的互溶共混物的不均匀性发挥重要作用？这样的共混物能够捕获初生晶体的形成，从而作为模型系统的晶体成核，在聚合物结晶领域中最重要的未解决的问题的调查？已知不同聚合物的混合是产生具有增强性能的新型合金的有效且具有成本效益的手段，并且具有重要的工业和基础意义。通过在两种聚合物之间形成强的分子间键合促进混合，但是对于这种强键合在改变分子和因此宏观性质中所起的确切作用知之甚少。第一部分的研究重点是调查分子间的键合强度的流动性的组成聚合物的混合物。第二部分旨在了解组分聚合物有序（结晶）对混合物流动性的影响。后者系统也将作为晶体成核研究的模型，这是聚合物结晶领域最重要的未解决问题。该计划在几个方面广泛影响材料研究领域。拟议的研究将为研究生和本科生创造学习机会，包括通过频繁的小组和小组间会议交流想法来培养团队合作技能。该计划的每个参与者都将参与宾夕法尼亚州立大学纳米科学中心（NSF材料研究科学与工程中心）广泛而重要的外展计划。最后，将与乔治弗劳达斯教授（美国）的研究小组进行合作研究。约阿尼纳，希腊），并与他的小组交换学生研究人员预计在这个计划的过程中。

TECHNICAL SUMMARY:Previous research on segmental and local dynamics of associating polymer blends and solutions, carried out with NSF-DMR support, focused on the roles of composition, intermolecular hydrogen bonding strength, and intrinsic component mobility differences. This research was conducted principally using dielectric spectroscopy, taking advantage of its ultra-broad frequency range and high sensitivity. This earlier work prompted a number of fundamental questions that will be answered through the proposed research. For example, what is the role of strong intermolecular coupling on the segmental dynamics when self-association of the component polymers is minimized? At what length scale does the segmental dynamics crossover from homogeneous to heterogeneous character? The second part of the proposed work seeks to establish the origin of a novel fast process observed in the dielectric spectra of miscible blends. The principle questions to be addressed in this part of the research include: Does component polymer crystallizability play an important role in determining heterogeneity of miscible blends between weakly associating polymers? Are such blends capable of capturing nascent crystal formation and hence serving as model systems for the investigation of crystal nucleation, the most significant unresolved problem in the field of polymer crystallization?NON-TECHNICAL SUMMARY:Mixing of unlike polymers is known to be an efficient and cost effective means of creating novel alloys with enhanced properties, and has important industrial and fundamental significance. Mixing is facilitated by the formation of strong intermolecular bonding between the two polymers, but little is known about the precise role such strong bonding plays in modifying molecular, and consequently macroscopic, properties. The first part of the proposed research focuses on the investigation of intermolecular bonding strength on the mobility of the component polymers in the mixture. The second portion seeks to understand the influence of component polymer ordering (crystallization) on mixture mobility. The latter systems will also serve as models for the investigation of crystal nucleation, the most significant unresolved problem in the field of polymer crystallization.This program broadly impacts the field of materials research in several ways. The proposed research will create learning opportunities for graduate and undergraduate students, including building teamwork skills from frequent group and inter-group meetings where ideas are exchanged. Each participant in the program will be engaged in the extensive and vital outreach program of the Penn State Center for Nanoscale Science, an NSF Materials Research Science and Engineering Center. Finally, collaborative studies will be undertaken with the research group of Prof. George Floudas (U. Ioannina, Greece), and an exchange of student researchers with his group is anticipated over the course of this program.