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

摘要- Han -9981972热塑性聚氨酯（TPU）由硬链段和软链段组成，硬链段由二异氰酸酯和短链二醇（作为扩链剂）组成，在使用温度下形成结晶相，软链段由控制低温性能的长链二醇组成。 目前商业上可获得的许多TPU的最不期望的特征是在约190- 220 ° C的加工温度下的热不稳定性，即，它们经历热降解和/或交联反应。 这主要是由于商业TPU中常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TPU的结构-形态-流变学关系。TPU的流变学行为与聚合物的形态状态密切相关。 更好地理解TPU的结构-形态-流变学关系，无论是否含有侧链液晶，都可以用来确定一致和最佳的加工条件。 PI计划在高温（170- 250 ℃）下使用原位红外光谱法研究氢键如何影响具有和不具有侧链液晶的TPU的形态，从而影响其流变性。 振荡，瞬态和稳态剪切流动行为的TPU合成与侧链液晶和没有将被调查。 这项研究完成后，可能会导致通过大分子结构的微小变化来创造特殊的超分子结构的可能性。

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.