CAREER:Reaction Dynamics of Polymerization and a Computer- Enhanced Dialectic in the Physical Chemistry Curriculum

理论和计算化学项目正在支持佐治亚理工学院的Rigoberto Hernandez教授，作为年轻科学家职业计划的一部分。这项研究的目的是表征聚合过程的时间依赖行为。一种新型晶格上的键渗流模型与类伊辛型聚合物生长哈密顿量(PGH)相结合，提供了非均匀和关联的成键/断键几率。它包括相关的反应动力学，但足够简单，以适应高(长)聚合物的蒙特卡罗处理。一个新的随机哈密顿量是围绕聚合物有效轮廓长度的平均力的势建立的。聚合物的宏观性质随其长度的增加而发生的变化是通过显式地依赖于该长度的有效摩擦来包含的。进一步研究这种哈密顿量的动力学，以及它与聚合物生长晶格哈密顿量之间的联系，应该能更好地理解单体性质和反应条件之间的联系，以及作为时间函数的聚合物材料性质。硬塑料、口香糖、胶水、蛋白质和涂层只是推动聚合物工业的各种聚合物材料的几个例子。令人惊讶的是，这些材料通常来自相同的碱性单体，只是反应条件和相对组成不同。现有的理论在描述最终产物时往往忽略了对粘性效应影响反应过程时的反应动力学的理解。这在用于微芯片封装的热固性聚合物中很重要；聚合结束不是因为反应物已经耗尽，而是因为由于粘度随反应程度的变化而急剧变化而导致的扩散猝灭。这项研究的目的是了解聚合物的反应性和材料粘度随温度和反应曲线的变化之间的竞争。这项建议的教育部分包括开发一门新的物理化学课程和一本配套的网络教科书，两者都强调理论理解和物理直觉之间的联系。课程还将使用各种电子通信形式。希望这种计算机增强的辩证法(CED)将为学生提供充分的机会，不仅学习如何回答问题，而且学习如何提出正确的问题。

The Theoretical and Computational Chemistry program is supporting Professor Rigoberto Hernandez at the Georgia Institute of Technology as part of the CAREER program for young scientists. The objective of this research is to characterize the time-dependent behavior of the polymerization process. A bond percolation model on a novel lattice has been combined with an Ising-like Polymer Growth Hamiltonian (PGH) to provide non-uniform and correlated bond formation/breaking probabilities. It includes the pertinent reaction dynamics, but is simple enough to accommodate the Monte Carlo treatment of high (long-length) polymers. A new stochastic Hamiltonian has been built around the potential of mean force for the effective polymer `contour` length. The change of the macroscopic properties of the polymer as its length increases is included through an effective friction which explicitly depends on this length. Further study of the dynamics of this Hamiltonian, as well as its connection to the polymer-growth lattice Hamiltonian, should provide increased understanding of the connection between the monomer properties and reaction conditions, and of the resulting material properties of the polymer as a function of time. Hard plastics, chewing gum, glues, proteins and coatings are but a few examples of the diverse range of polymeric materials which have driven the polymer industry. Surprisingly, these materials are often obtained from the same base monomers, varying only reaction conditions and relative composition. What existing theories often leave out in their characterization of the final product is an understanding of the reaction dynamics when viscous effects affect the reaction process. This is important in thermoset polymers used in the encapsulation of microchips; the polymerization ends not because the reactants have been depleted, but because of diffusional quenching due to the dramatic change in viscosity as a function of the extent of reaction. The goal in this research is to understand the competition between the reactivity of the polymer and changes in the material's viscosity as a function of temperature and reaction profile. The educational component of this proposal comprises the development of a new physical chemistry course and a companion web-based textbook, both of which emphasize the connection between theoretical understanding and physical intuition. The course will also use various electronic forms of communication. It is hoped that this computer-enhanced dialectic (CED) will provide ample opportunity for the student to learn not only how to answer questions, but also how to ask the right ones.