FRG: Structure and Dynamics of Reversible Model Gels

这是一个重点研究组奖，结合合成，表征和流变强度的聚合物凝胶的研究。 具体而言，静态和动态光散射和流变学测量将进行两个模型可逆凝胶，以阐明宏观行为的relationship的基本热力学和分子动力学。 凝胶之一将包含水溶性遥爪聚合物和具有与聚合物的端基共轭的基团的小分子交联剂。 这些遥爪聚合物端基将与交联位点、遥爪聚合物的分子量分布和交联剂的官能度可逆地缔合。 这些将是不同的，以探索其对模型凝胶的结构和动力学的影响。 另一种体系将包括ABC三嵌段共聚物，其具有互不相容的A、B和C嵌段，其中B而不是A和C可以在水中溶胀。 在高温下，A和C嵌段将是流体，允许形成材料，但在低温下，预计A和C将是玻璃状胶束，C被排除在A胶束之外，反之亦然。 凝胶的非遍历特性将是特别感兴趣的，并且其随加工条件的变化将通过光散射测量来表征。 然后将确定凝胶的粘弹性，并考虑由光散射和凝胶合成所施加的已知化学特性确定的结构和动力学。凝胶是“软物质”的一个重要类别，这种多学科和跨学科的方法应该提供显着的教育利益，除了促进我们的理解参与的学生。

This is a Focused-Research Group award combining synthetic, characterization, and rheological strength to the study of polymer gels. Specifically, static and dynamic light scattering and rheological measurements will be carried out on two model reversible gels to elucidate the realtion of macroscopic behavior to the underlying thermondynamics and molecular dynamics. One of the gels will comprise a water soluble telechelic polymer and a small molecule crosslinker with groups conjugate to the endsgroups of the polymer. These telechelic polymer endgroups will reversibly associate with the crosslink loci, the distributions of molecular weight of the telechelic polymer, and the functionality of the crosslinker. These will be varied to explore their effects on the structure and dynamics of the model gel. The other system will comprise an ABC triblock copolymer, with mutually incompatible A,B and C block where B, but not A and C may be swollen in water. At high temperatures the A and C blocks will be fluid, permitting the material to be formed, but at low temperatures it is anticipated that A and C will be glassy micelles, with C excluded from A micelles and vice versa. The nonergodic character of the gels will be of particular interest, and the variation of this with processing conditions will be characterized by light scattering measurements. Then viscoelastic properties of the gels will be determined and considered in terms of the structure and dynamics determined by light scattering and the known chemical characteristics imposed by the gel synthesis. Gels are an important category of "soft matter" and this multi- and inter-disciplinary approach should provide significant educational benefits to the students involved in addition to advancing our understanding.