Synthesis of transparent and soluble poly(amide-imide) containing trifluoromethyl groups

Abstract

Aromatic poly(amide-imide)s are high-performance polymers used in various fields owing to their outstanding chemical resistance, thermal and mechanical properties. In addition, various properties, such as thermal stability, optical properties, and thermal expansion characteristics, can be adjusted by modifying the structure from the design stage of monomers. However, their strong inter-chain interaction via a formation of charge transfer complex cause intensive coloration. Because of the same reason, it has low solubility to common organic solvents causing processing difficulties. These disadvantages can be overcome by introducing flexible linkages, bulky pendant groups into polymer backbone or using non-coplanar structures. Due to its twisted structure, -CF3 moiety is expected to reduce the chain packing of poly(amide-imide)s and to provide transparent, soluble poly(amide-imide)s. In this study, we designed a new amine monomer containing a trifluoromethyl group and a biphenyl group. A series of poly (amide-imide)s were synthesized using this new monomer. Through experiments, it was confirmed that the higher the proportion of trifluoromethyl group, the higher the thermal stability and the lower the thermal expansion coefficient.