The synthesis and X‐ray structure of 1,2,3,4‐cyclobutane tetracarboxylic dianhydride and the preparation of a new type of polyimide showing excellent transparency and heat resistance

Some polyimide films based on cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CBDA) and aromatic diamines were synthesized to investigate their temperature resistance and percent transmission of light. The preparations of CBDA were investigated; they produced almost 10 times the yield of CBDA in comparison to yields obtained by previous methods. The configuration of CBDA was determined by X‐ray analysis to be cis–trans–cis. The polymer films showed excellent thermal resistance and were transparent and colorless, desirable characteristics for practical applications in the field of polymer engineering. However, the polymer obtained from a pyromellitic dianhydride instead of from CBDA was deep yellow and not desirable for high‐qualified display materials such as liquid‐crystal displays. The percent transmission of the polymers obtained from CBDA and aromatic diamines ranged from 81.5 to 85.8%, whereas the deep‐yellow polymers showed low percent transmissions ranging from 48 to 63.9%. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 108–116, 2000