Structure-Morphology-Rheology Relationships in Thermally Stable TPU Having Side-Chain Liquid Crystals

HAN-9981972热塑性聚氨酯(TPU)由二异氰酸酯和短链二醇(作为扩链剂)组成的硬段和控制低温性能的长链二醇组成的软段组成，它们在使用温度下形成结晶相。目前市面上可获得的许多热塑性聚氨酯中，最不理想的特征是在大约190-220摄氏度的加工温度下不稳定，即它们经历了热降解和/或交联化反应。这主要是由于商业热塑性聚氨酯中经常使用的芳香族二异氰酸酯的热不稳定性。PI计划研究具有侧链液晶的热稳定热塑性聚氨酯的结构-形态-流变学关系。热塑性聚氨酯的流变行为与聚合物的形态状态密切相关。更好地了解含或不含侧链液晶的TPU中的结构-形态-流变学关系，可以用来确定一致和最佳的加工条件。PI计划使用高温(170-250oC)下的原位红外光谱，研究氢键如何影响带有和不带有侧链液晶的TPU的形态，从而影响其流变性。研究了含和不含侧链液晶的热塑性聚氨酯的振荡、瞬时和稳态剪切流动行为。这项研究完成后，可能会通过改变大分子的结构来创造特殊的超分子结构。

Abstract - Han - 9981972Thermoplastic polyurethane (TPU) consists of hard segments composed of diisocynate and short-chain diols (as chain extender) which form a crystalline phase at service temperatures, and soft segments composed of long-chain diols which control low temperature properties. The most undesirable feature of the many TPUs currently available commercially is thermal instability at processing temperatures, approximately 190-220oC, i.e., they undergo thermal degradation and/or crosslink reactions. This is primarily due to the thermal instability of aromatic diisocyanates often used in commercial TPUs. The PI plans to investigate structure-morphology-rheology relationships in thermally stable TPUs having side-chain liquid crystals.The rheological behavior of TPUs is intimately related to the morphological state of the polymer. A better understanding of structure-morphology-rheology relationships in TPU with or without side-chain liquid crystals, can be used to determine consistent and optimum processing conditions. The PI plans to investigate how hydrogen bonding might affect the morphology and thus the rheology of TPU with and without side-chain liquid crystals using in situ infrared spectroscopy at elevated temperatures (170-250oC). Oscillatory, transient, and steady-state shear flow behaviors of the TPUs synthesized with and without side-chain liquid crystals will be investigated. The research, when completed, may lead to the possibility of creating special supramolecular structures by means of small changes in the architecture of the macromolecules.