柔性电子技术的进步,特别是可折叠显示器和显示器下摄像机(UDC)的进步,对高性能无色聚酰亚胺(CPI)产生了迫切的需求。然而,当前的CPIs对于衬底应用缺乏足够的耐热性。在这项工作中,设计了四种刚性螺二芴二胺,和相应的聚酰亚胺通过它们与5,5'-(全氟丙烷-2,2-二基)双(异苯并呋喃-1,3-二酮)(6FDA)或9,9-双(3,4-二羧基苯基)芴二酐(BPAF)缩合而制备。刚性和共轭螺二芴单元赋予聚酰亚胺356至468°C的较高玻璃化转变温度(Tg)。它们的光学性质受到小侧基和具有周期性扭曲的分子构象的螺二芴结构的调节。因此,获得平均透射率为75%至88%且黄度指数(YI)低至2.48的一系列CPIs。其中,27SPFTFA-BPAF具有优异的综合性能,Tg为422°C,a5wt.%损失温度(Td5)为562°C,aYI为3.53,抗拉强度(δmax)为140MPa,分别。通过实验比较和理论计算研究了结构-性质关系的机理,所提出的方法为光电工程设计具有优异热稳定性和透明性的高刚性共轭CPIs提供了途径。
Advancements in flexible electronic technology, especially the progress in foldable displays and under-display cameras (UDC), have created an urgent demand for high-performance colorless polyimide (CPI). However, current CPIs lack sufficient heat resistance for substrate applications. In this work, four kinds of rigid spirobifluorene diamines are designed, and the corresponding
polyimides are prepared by their condensation with 5,5\'-(perfluoropropane-2,2-diyl) bis(isobenzofuran-1,3-dione) (6FDA) or 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride (BPAF). The rigid and conjugated spirobifluorene units endow the
polyimides with higher glass transition temperature (Tg) ranging from 356 to 468 °C. Their optical properties are regulated by small side groups and spirobifluorene structure with a periodically twisted molecular conformation. Consequently, a series of CPIs with an average transmittance ranging from 75% to 88% and a yellowness index (YI) as low as 2.48 are obtained. Among these, 27SPFTFA-BPAF presents excellent comprehensive performance, with a Tg of 422 °C, a 5 wt.% loss temperature (Td5) of 562 °C, a YI of 3.53, and a tensile strength (δmax) of 140 MPa, respectively. The mechanism underlying the structure-property relationship is investigated by experimental comparison and theoretical calculation, and the proposed method provides a pathway for designing highly rigid conjugated CPIs with excellent thermal stability and transparency for photoelectric engineering.