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

摘要：热塑性聚氨酯（TPU）由在使用温度下形成结晶相的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。目前市面上许多tpu最不理想的特性是在加工温度下（约190-220℃）的热不稳定性，即它们会发生热降解和/或交联反应。这主要是由于商业tpu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tpu的结构-形态-流变关系。tpu的流变行为与聚合物的形态状态密切相关。更好地了解有或没有侧链液晶的TPU的结构-形态-流变关系，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研究氢键如何影响有或没有侧链液晶的TPU的形态和流变学。将研究有侧链液晶和无侧链液晶合成的tpu的振荡、瞬态和稳态剪切流动行为。这项研究完成后，可能会通过大分子结构的微小变化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.