The key component currently missing for the next generation of transparent and flexible displays is a high-performance polymer material that is flexible, while showing optical and thermal properties of glass. It must be transparent to visible light and show a low coefficient of thermal expansion (CTE). While specialty plastics such as aromatic polyimides are promising, reducing their CTE and improving transparency simultaneously proved challenging, with increasing coloration the main problem to be resolved. We report a new poly(amide-imide) material that is flexible and displays glass-like behavior with a CTE value of 4 parts per million/°C. This novel polymer was successfully used as a substrate to fabricate transparent and flexible indium-gallium-zinc oxide thin-film transistors.

Soluble and transparent poly(amide‐imide)s (PAIs) with a glass transition temperature over 300 °C were synthesized from the alicyclic diacid monomers containing a biphenyl unit with two trifluoromethyl (CF3) groups. Combination of two isomeric biphenyl units with CF3 groups significantly improves the glass transition temperature of the corresponding PAIs. The increase of unsymmetrical biphenyl units increased the glass transition temperature of the polymers by reducing the average chain packing distance.