Dynamics of Highly Constrained Polymer Chains

9910386fuller本研究旨在了解受支链结构或部分结晶度约束的聚合物链的静态和动态特性。一个具体的目标是研究长链分支和低结晶度如何影响聚合物的流变学和物理性质。这些材料的流变性比线性、非晶链所表现出的要复杂得多，其中重复是控制取向松弛的主要机制。实验方法将结合光学双折射和红外二色性技术来研究约束和部分约束聚合物链的组分弛豫动力学。对于长链支链聚合物，我们计划解决长链分支为什么以及如何作为受应变影响的聚合物链的分子约束。进一步的目标是研究链受低结晶度约束的半晶嵌段聚合物的弛豫动力学。窄分子量长链支链聚乙烯是一种具有优异物理性能和良好加工特性的新型材料。这些材料最近作为一种新型聚乙烯薄膜大规模投入市场。人们对这种优异的性质组合的分子起源知之甚少；更好的理解可能会导致合理的策略，以改善这类重要的商品塑料的性能和加工特性。

9910386FullerThe studies in this seek to understand the static and dynamic properties of polymer chains constrained by branched architectures or partial crystallinity. A specific objective is to investigate how long-chain branching and low levels of crystallinity influence the rheological and physical properties of polymers. The rheology of these materials is much more complicated than exhibited by linear, amorphous chains where reptation is the principal mechanism governing the relaxation of orientation. The experimental approach will combine synthesis with optical birefringence and IR dichroism techniques to investigate the component relaxation dynamics of constrained and partially-constrained polymer chains. For long-chain branched polymers we plan to address why and how a long-chain branch acts as a molecular constraint on polymer chains subjected to strains. A further objective is to investigate the relaxation dynamics of semi-crystalline block polymers whose chains are constrained by low levels of crystallinity.Narrow molecular weight, long-chain branched polyethylenes represent a new composition of matter that have both excellent physical properties and good processing characteristics. These materials have recently been introduced into the market on a large scale as a new class of polyethylene films. The molecular origins of this excellent combination of properties are poorly understood; a better understanding might lead to rational strategies to improve the properties and processing characteristics of this important class of commodity plastics.