Effect of Chemical Structure and Molecular Architecture on the Properties of Polymer Networks

9706066科恩这个重点研究小组的项目涉及弹性体性能的基础研究。拟议的研究包括三个方面的方法：1)仔细的合成和表征；2)使用氢核磁共振；3)蒙特卡罗模拟。该小组将使用末端连接化学以系统的方式改变准备好的网络的结构，并检查这种变化对网络的机械和膨胀特性的影响。我们将利用重氢核磁共振实验来探索网络的分子结构和压缩条件下网络的链段取向有序参数。最后，开发蒙特卡罗模拟方法来考察固化后得到的分子结构、网络的膨胀机理以及前体分子的链刚性的影响。实验结果、模型预测和仿真结果将进行比较，以验证或改进现有模型，并在必要时提出新的模型。这些关于聚二乙基硅氧烷(PDE)网络的研究将有助于阐明一个长期存在的问题，即张力网络中的链段-链段相互作用的性质，因为PDE在其玻璃化转变过程中表现出介相结构。%这项研究在弹性材料和网络领域具有重要的技术意义，有助于从根本上了解它们的分子级结构和性能。***

9706066 Cohen This Focused Reqearch Group project involves fundamental studies of elastomer properties. The proposed research consists of a three-pronged approach involving: 1) careful synthesis and characterization; 2) use of deuterium NMR; and 3) Monte Carlo simulations. The group will use end-linking chemisty to vary the architecture of the prepared networks in a systernatic way and to examine the effect of this variation on the mechanical and swelling properties of the networks. Deuterium NMR experiments will be used to probe the molecular architecture of the networks and the segment orientational order parameter of networks under compression. Finally, Monte Carlo simulation methods will be developed to examine the molecular structures that are obtained after curing, the swelling mechanisms of the networks and the effect of the chain stiffness of the precursor molecules. Experimental results, model predictions and simulation results will be compared to validate or improve existing models as well as propose new models if necessary. These studies on poly(diethylsiloxane) (PDES) networks will help elucidate a long standing issue about the nature of segment-segment interactions in strained networks because PDES exhibits a mesophasic structure above its glass transition. %%% This research is in the technologically important area of elastomeric materials and networks and will help provide fundamental understanding of their molecular-level structures and properties. ***