FRG: Structure and Dynamics of Reversible Model Gels

这是一项重点研究小组奖，将合成、表征和流变强度结合到聚合物凝胶的研究中。具体来说，将对两个模型可逆凝胶进行静态和动态光散射和流变学测量，以阐明宏观行为与潜在的热力学和分子动力学的关系。其中一种凝胶将包括一种水溶性遥爪聚合物和一种小分子交联剂，该交联剂的端基与聚合物的端基共轭。这些遥链聚合物端基将可逆地与交联点、遥链聚合物的分子量分布和交联剂的官能度相关联。这些将是不同的，以探索它们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，具有互不相容的A、B和C嵌段，其中B，而不是A和C可以在水中膨胀。在高温下，A和C块将是流体，从而允许材料形成，但在低温下，预计A和C将是玻璃胶束，C从A胶束中排除，反之亦然。凝胶的非遍历特性将特别令人感兴趣，这种特性随加工条件的变化将通过光散射测量来表征。然后，将根据光散射所确定的结构和动力学以及凝胶合成所强加的已知化学特性来确定和考虑凝胶的粘弹性特性。凝胶是“软物质”的一个重要类别，这种多学科交叉的方法除了增进我们的理解外，还应该为参与其中的学生提供显著的教育好处。

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.