Presidential Faculty Fellows

摘要由多功能单体光聚合而成的高交联聚合物适用于光学透镜、光纤涂层、二次谐波产生材料和牙科材料等应用。这些类型的材料具有优异的热稳定性和尺寸稳定性，但它们的应用受到聚合反应的某些方面的限制。聚合物网络的高度交联结构和相关的低迁移率导致非均相聚合物网络的形成、自加速动力学和反应扩散控制终止。这些聚合的非均相性质可能导致机械强度降低500倍，因此，了解反应条件和聚合物结构之间的关系对于开发改进材料至关重要。这项工作的重点是这些聚合的基本特征，以及用于二次谐波产生材料等应用的材料的开发。聚合反应的多甲基丙烯酸酯，多丙烯酸酯和其他多乙烯基化合物将被研究，以确定如何反应条件影响聚合物的结构演变。结构演变将通过多种技术，包括介电光谱、透射电子显微镜和电子自旋共振光谱来表征。这些标准技术将与我们最近应用于聚合系统的两种新技术一起使用：光致变色和二次谐波产生。这些技术能够探测微观结构，从而获得有关非均质性和自由体积分布的定量信息。这些技术的实验结果将与动力学凝胶模拟的理论预测相结合，以获得反应条件（如温度、引发剂浓度和单体类型）如何影响交联聚合物的非均质性和机械性能的完整图像。

CTS-9453369 Christopher N. Bowman/University of Colorado @ Boulder ABSTRACT Highly crosslinked polymers produced from photopolymerizations of multifunctional monomers are suitable for applications as optical lenses, optical fiber coatings, second harmonic generation materials, and dental materials. These types of materials have excellent thermal and dimensional stability, but their application has been limited by certain aspects of the polymerization reaction. The highly crosslinked structure of the polymer networks and the associated low mobilities lead to the formation of a heterogeneous polymer network, autoacceleration kinetics, and reaction diffusion controlled termination. The heterogeneous nature of these polymerizations may cause up to a 500 fold decrease in the mechanical strength, and thus, understanding the relationship between reaction conditions and polymer structure is of the utmost importance in developing improved materials. This work focuses on a fundamental characterization of these polymerizations, as well as the development of materials for applications such as second harmonic generating materials. Polymerization reactions of multimethacrylates, multiacrylates, and other multivinyl compounds will be studied to determine how reaction conditions affect the polymer structural evolution. The structural evolution will be characterized by a variety of techniques including dielectric spectroscopy, transmission electron microscopy, and electron spin resonance spectroscopy. These standard techniques will be used along with two novel techniques that we have recently applied to polymerizing systems: photochromism and second harmonic generation. These techniques are capable of probing the microscopic structure so that quantitative information regarding the heterogeneity and free volume distribution can be obtained. The experimental results from these techniques will be coupled with theoretical predictions from kinetic gelation simulations to obtain a complete pictu re of how reaction conditions such as temperature, initiator concentration, and monomer type affect the heterogeneity and mechanical properties of the crosslinked polymer.