Structure and Dynamics of Polymer Blends Exhibiting Strong Intermolecular Interactions

这项工作的第一个目标是利用轻拍模式原子力显微镜，直接在片层水平上定量研究模型聚合物共混物的结晶和结构形成。一些问题是发展一个完整的理解聚合物结晶的关键，在整齐的状态下和在熔融可混合的混合物中，将被解决。例如，板层生长是均匀进行的，还是局部生长速度依赖于时间，并随板层之间的变化而变化？高Tg、无定形聚合物稀释剂的存在对这个问题和其他基本问题的答案有何影响？为了补充实验工作，研究结果将与有限元模型的预测进行比较。该项目的第二个目标是深入了解表现出分子间氢键的可混溶聚合物共混物的动力学，如介电光谱所探测的那样。这方面的研究很少，特别是关于分子间相互作用对玻璃态的脆性和氢键动力学的影响。这项工作的动机部分是由于目前人们对热可逆网络和氢键、自组装超分子结构的兴趣。介电实验的重点将放在共聚物的模型二元共混物上，其中分子间氢键的数量可以通过改变共聚物的组成来系统地改变。本研究中的某些混合物将满足LRC模型对可逆网络动力学的假设，并将为该模型提供良好的检验。最后，在NSF-MRI赠款的支持下，一种混合仪器正在开发中，该仪器将能够同时进行介电和二维红外光谱测量。这一新的仪器无疑将对上述研究产生重要影响。这项研究的结果将对我们理解结晶聚合物和聚合物共混这两个在工业领域具有重要意义的领域产生广泛的影响。除了对参与研究活动的研究生和本科生产生直接的教育影响外，研究成果还将被纳入PI教授的研究生水平课程。研究成果将通过在同行评议的期刊上发表，以及通过国际和平协会和小组成员在重大科学会议上的发言来传播。

The first objective of this effort is a quantitative investigation of crystallization and structure formation in model polymer blends directly at the lamellar level, using tapping mode atomic force microscopy. A number of questions that are key to developing a complete understanding of polymer crystallization, in the neat state and in melt-miscible blends, will be addressed. For example, does lamellar growth proceed uniformly, or are local growth rates time-dependent and variable from lamella to lamella? How are the answers to this and other fundamental questions influenced by the presence of a high Tg, amorphous polymer diluent? To supplement the experimental work, findings will be compared with predictions of a finite element model. The second objective of the project is to develop insight into the dynamics of miscible polymer blends exhibiting intermolecular hydrogen bonding, as probed by dielectric spectroscopy. There has been little research in this area, particularly with respect to the influence of intermolecular interactions on the fragility of the glassy state and the dynamics of hydrogen bonding. The motivation for this work was partly shaped by current interest in thermoreversible networks and hydrogen-bonded, self-assembling supramolecular structures. The focus of the dielectric experiments will be on model binary blends of copolymers in which the number of intermolecular hydrogen bonds can be systematically varied by changing copolymer composition. Certain blends in this study will satisfy the assumptions of the LRC model for the dynamics of reversible networks, and will provide a good test of the model. Finally, with the support of an NSF - MRI grant, a hybrid instrument is under development that will be capable of performing simultaneous dielectric and two-dimensional infrared spectroscopic measurements. This new instrument will undoubtedly have an important impact on the research described above.The results of this research will have broad impact on our understanding of both crystalline polymers and polymer blends, areas of great importance in the industrial sector. In addition to the direct educational impact on graduate and undergraduate students involved in the research activity, research results will be incorporated into graduate level courses taught by the PI. Research findings will be disseminated through publication in peer-reviewed journals, as well as through presentations by the PI and group members at major scientific meetings.