Cooperative Molecular Motions in Glassy Polymers

该研究的目的是解决一些高温玻璃聚合物中亚tg弛豫的性质。研究了聚碳酸酯和其他刚性芳香族骨架玻璃聚合物的弛豫行为。双酚a聚碳酸酯的低温弛豫具有广泛的链内协同特性。这种协同运动被认为是聚碳酸酯具有优异机械性能的关键。通过使用定制的分子结构和动态力学测量，可以更好地理解这种链内协同性的起源和其他类型玻璃聚合物的弛豫行为。一旦理解了协同运动的起源，一个重要的问题将得到回答：这种协同运动的规模如何影响分子间的相互作用？动态体松弛实验将用于解决这个问题。在提出的研究中要回答的另一个问题是，协同运动的规模如何影响聚合物在延展性和脆性方面的机械性能。通过本研究，将进一步明确分子结构、弛豫和力学性能之间的关系，并为设计和合成具有理想性能的新型高温延展性聚合物提供指导。

The aim of the research is to address the nature of sub-Tg relaxations in some high-temperature glassy polymers. The relaxation behaviors of polycarbonates and other rigid aromatic backbone glassy polymers will be investigated. The low-temperature relaxation of bisphenol-A polycarbonate has an extensive in-chain cooperative character. This cooperative motion is thought to be the key to polycarbonate's superior mechanical properties. The origin of this in-chain cooperativity and the relaxation behavior of other kinds of glassy polymers can be better understood by using tailored molecular architectures together with dynamic mechanical measurements. Once the origin of cooperative motion is understood, an important question will be answered: How does the scale of this cooperative motion affect intermolecular interactions? Dynamic bulk relaxation experiments will be used to address this question. Another question to be answered in the proposed research deals with how the scale of cooperative motion affects the mechanical properties of the polymer in terms of ductility and brittleness. Through this research, the relationships between molecular structure, relaxation and mechanical properties will be further clarified and the results can be used as guidelines to design and synthesize new high-temperature ductile polymers with desirable properties.