Tuning the heat resistance properties of polyimides by intermolecular interaction strengthening for flexible substrate application

Publication date: Available online 21 April 2019Source: PolymerAuthor(s): Meng Lian, Feng Zheng, Xuemin Lu, Qinghua LuAbstractIntrinsic polyimides (PIs) with high glass transition temperature (Tg), excellent thermal stability, and favorable mechanical properties have been in great demand in recent years with the rapid development of flexible displays. In this work, an interchain-interaction “strengthener” has been introduced to obtain PIs with improved thermal resistance and stability. Benzimidazole-based diamines imparting rigidity, conjugation, crosslinking, and especially hydrogen bonding have been incorporated into benzoxazole-polyimide. Frequency shifts in the IR bands spectra of CO and NH bonds were indicative of strong hydrogen bonding in benzimidazole-incorporating PIs, resulting in an increase in Tg from 333 °C to 442 °C. Furthermore, because of more extensive hydrogen bonding, PIs containing bis-benzimidazole units exhibited much higher crystallinity and Tg than those containing mono-benzimidazole units. The 5% weight loss temperature (Td5) was above 550 °C because of the rigidity of the conjugated structure and the tightly packed state of the polymer chains. Tg and Td5 of PIs annealed in air were higher than those of samples annealed in vacuo, whereas the opposite trend was seen in crystallinity and mechanical properties. Finally, we delineated the effects of intermolecular interaction strengthener and annealing atmosphere on the properties of PIs, whi...

Source: Polymer - April 22, 2019 Category: Chemistry Source Type: research