Here, we report superheat-resistant polymers, poly(benzoxazole imide)s (PBOI), with very low co-efficients of thermal expansion (CTE) and sufficient ductility for applications as the plastic substrates of organic light-emitting diode (OLED) displays. Diamines incorporating benzoxazole (BO) units were synthesized for this purpose. A PBOI derived from a BO-containing diamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) has excellent properties that are superior to those of s-BPDA/p-phenylenediamine (p-PDA) polyimide such as an undetectable T-g, a very low CTE (9.6 ppm K-1), a very high the 5% weight loss temperature (T-d(5)= 592 degrees C) in N-2, and good ductility while remaining the highest level of non-flammability (UL-94, V-0). The use of another BO-incorporating diamine permitted further improvement in the target properties: an extremely high T-d(5)(609 degrees C) in N-2 and a considerably low CTE (3.3 ppm K-1) close to that of a silicon wafer. These results show that the PBOIs examined in this work are promising candidates for use as the plastic substrates in OLED displays. (C) 2017 Elsevier Ltd. All rights reserved.