DMR-Dynamics of Branch Point Motion in Entangled Polymers

在此授权下，滑动链接算法将扩展到聚合物的情况下，多个分支点，分支点运动的理论是必需的。 作为一个测试案例，将考虑一系列不对称的星，从第三臂长度为零的星（因此是线性聚合物）到第三臂长度等于其他两个的星（对称星星）。 这一系列聚合物的实验弛豫行为将被预测，包括迄今为止意想不到的发现，即使是只有两个或三个纠缠的小的第三臂减慢星星的动力学比现有的动态稀释理论预测的要多得多，使得短臂在减缓弛豫方面几乎与长得多的臂一样有效。 滑动链接模型的成功意味着该算法有可能准确地捕获分支点运动的物理特性，这是理解更复杂的H和梳状聚合物的动力学的必要条件，以及这些与线性聚合物和彼此的混合物。 因此，滑动链接算法将扩展到H和梳状分子的情况下，其松弛性能的分支点动力学的效果将进行探讨，比较模型的预测与最近获得的实验数据。 我们还将探索分支点运动与一个更复杂的真实空间滑动链接模型，最近已开发的同事在名古屋大学。 我们的目标是获得一个准确的理论，分支点运动，这是最重要的缺失成分所需的发展一般理论的聚合物熔体松弛。 从这些模拟得到的结果将被纳入一个一般的分层模型松弛一般多分散支化聚合物熔体，从而提高我们的能力，使用流变学理论推断分子支化结构的流变数据，这是一个重要的实用和商业价值的目标。 这项研究将继续与日本名古屋大学的土井正夫小组进行国际合作。该理论研究项目将PI的成功模型扩展到其他聚合物结构。 然后，模型将能够更好地描述聚合物熔体松弛和随后的聚合物流动。 相反，使用该理论，弛豫测量将产生关于聚合物的分子支化结构的信息。 这项工作将与日本名古屋大学的一个小组合作进行。

Under this grant, the slip-link algorithm will be extended to the case of polymers with multiple branch points, for which a theory for branch-point motion is required. As a test case, a series of asymmetric stars will be considered, ranging from one with a zero-length third arm (which is therefore a linear polymer) to one whose third arm has length equal to the other two (a symmetric star). The experimental relaxation behavior for this series of polymers will be predicted, including the hitherto unexpected finding that even a small third arm with only two or three entanglements slows down the dynamics of the star much more than predicted by existing dynamic dilution theories, making a short arm nearly as effective as a much longer arm in slowing down the relaxation. This success of the slip-link model implies that the algorithm has the potential to capture accurately the physics of branch-point motion, which is a necessary requirement for understanding the dynamics of more complex H and comb polymers, as well as mixtures of these with linear polymers and with each other. The slip link algorithm will thus be extended to the cases of H and comb molecules and the effect of branch point dynamics on their relaxation properties will be explored, comparing the predictions of the model with recently obtained experimental data. We will also explore branch-point motion with a more sophisticated real-space slip-link model that has been recently developed by colleagues at Nagoya University. The goal is to obtain an accurate theory of branch-point motion, which is the most important missing ingredient required for development of general theories of polymer melt relaxation. The results obtained from these simulations will be incorporated into a general hierarchical model for relaxation of general polydisperse branched polymer melts, thus enhancing our ability to use rheological theory to infer molecular branching structure from rheological data, which is an important practical and commercially valuable goal. The research will continue international collaborations with the group of Masao Doi at Nagoya University in Japan. %%%This theoretical research project will extend the PI's successful models to other polymer structures. The models will then be able to better describe polymer melt relaxation and subsequently the flow of polymers. Conversely, using this theory, relaxation measurements will yield information about molecular branching structure of polymers. The work will be done in collaboration with a group at Nagoya University, Japan.***