Interplay of Segmental and Global Dynamics in Cross-Linking Networks

本研究是对一类重要的复杂体系，即化学交联聚合物网络的系统研究。 有关这些系统的动态信息将通过宽带介电弛豫光谱和动态力学光谱实验产生，并将对适当的模型进行验证。 拟议的研究增加了一个主要的新的维度，在聚合物网络的动力学的早期研究中，选择的系统的研究维度，在聚合物网络的动力学的早期研究中，选择的系统的研究表现出，除了横向偶极矩分量，一个持久的累积偶极矩沿着的链轮廓，可以通过正常模式过程放松。 当重复单元缺乏垂直于链轮廓的对称平面时，存在聚合物分子的这部分偶极矩。 对于n个这样的单元的序列，偶极矢量必须与位移矢量相关，因此从正常过程的研究中，人们不仅可以确定弛豫时间，而且可以确定均方端到端距离。 因此，选择用于研究的网络形成材料将具有独特的特性，因为它们的分子结构将有助于检测分子运动的整个层次，从局部到片段再到全局。 可以预见，在结构和地形的控制变化将导致在定制网络的能力与所需的特性，其响应可以通过选择性的时间尺度上的参与比每个动态过程的特征时间更短或更长的变化。 最后，通过分子概念来认识网络的宏观性质将成为可能。5.拟议的研究将具有比上述目标更广泛的影响。 这是因为各种长度尺度的动力学的相互作用对许多其他复杂系统的行为至关重要，例如自组装和各种纳米结构，以及从基因治疗，蛋白质动力学和蛋白质折叠到影响DNA局部和全局动力学的环和十字形的生物相关问题的主机。 研究和教育的整合将通过本科生和研究生的讲座和实验室课程来实现。 拟议的工作还将有助于加强族裔多样性，在理工学院的YES（青年工程和科学）暑期方案的主持下，为来自纽约市高中的一些代表性不足的少数族裔学生提供住宿。

This research is for a systematic study on one important type of complex systems, namely chemically cross-linked polymer networks. Information about the dynamics of these systems will be generated experimentally by broad-band dielectric relaxation spectroscopy and dynamic mechanical spectroscopy, and will be verified against the appropriate models. The proposed research adds a major new dimension to the earlier studies of dynamics in polymer networks in that the systems selected for study dimension to the earlier studies of dynamics in polymer networks in that the systems selected for study exhibit, in addition to the transverse dipole moment component, a persistent cumulative dipole moment along the chain contour that can be relaxed via the normal mode process. This part of the dipole moment of the polymer molecules is present when the repeat unit lacks a plane of symmetry perpendicular to the chain contour. For a sequence of n such units, the dipole vector must correlate with the displacement vector and thence from the studies of the normal processes one can determine not only the relaxation time but also the mean square end-to-end distance. Therefore, the network-forming materials chosen for study will have a unique characteristic in that their molecular architecture will be conducive to the detection of the entire hierarchy of molecular motions, ranging from local to segmental to global. It is anticipated that the controlled variation in the structure and topography will result in the ability to tailor-make networks with desired characteristics whose response can be varied by a selective engagement on the time scales shorter or longer than the characteristic time of each dynamic process. Ultimately, it will be possible to realize the macroscopic properties of the networks by molecular concepts.%%5The proposed research will have implications broader than the aforementioned goals. This is so because the interplay of dynamics of various length scales is crucial to the behavior of many other complex systems, such as self-assemblies and various nanostructures, as well as to the host of bio-related issues that range from gene therapy, protein dynamics and protein folding to the loops and cruciforms that affect the local and global dynamics of DNA's. The integration of research and education will be realized through lectures and laboratory courses for undergraduate and graduate students. The proposed work will also contribute to the enhancement of ethnic diversity by accommodating a number of under-represented minority students from New York City high schools under the aegis of the YES (Youth in Engineering and Science) summer program at Polytechnic.