Thermoplastic polyurethanes (TPU) produced in the reaction of hexamethylene diisocyanates (HDI) and diols are widely applied in industry. The phase transition behavior of the HDI-diol hard domain was investigated as a structural analog to conventional polyamides (PA), wherein an oxygen atom substituted a methylene group. This substitution brought about a distinct phase transition behavior; the apparent merging of two diffraction peaks into the intermediate peak was not observed; upon heating, the methylene groups orderly packed in the crystalline domain in a trans conformation, gradually transforming into a disorderly gauche conformation was also absent. Such a transition observed in this work is not in accordance with the Brill transition no matter that it is defined by apparent experimental criterion or essential molecular fundamental. The melting sequences of the phase transition, i) mesophase; ii) crystallites; iii) blocks mixing, were jointly revealed by multiple in-situ techniques, WAXS, FTIR and SAXS.

由六亚甲基二异氰酸酯（HDI）和二醇反应生成的热塑性聚氨酯（TPU）在工业上有着广泛的应用。研究了 HDI-二醇硬域的相变行为，作为传统聚酰胺 (PA) 的结构类似物，其中氧原子取代了亚甲基。这种替代带来了明显的相变行为；没有观察到两个衍射峰明显合并为中间峰；加热后，亚甲基基团以反式构象有序堆积在结晶域中，逐渐转变为无序的左旋构象也不存在。在这项工作中观察到的这种转变不符合布里尔转变，无论它是由明显的实验标准或基本分子基础定义的。相变的熔化序列，i) 中间相；ii) 微晶；iii) 块混合，由多种原位技术、WAXS、FTIR 和 SAXS 联合揭示。