Preparation and characterization of aromatic polyimides and related copolymers

Copolyimides containing BTDA-3DDS and BTDA-4ODA units have been synthesized by solution imidization methods. The copolyimides have high T_g's (267–283°C) and high decomposition temperatures (540–575°C; nitrogen); both properties are dependent on composition. Those copolymides with low concentrations of BTDA-4ODA are generally soluble in organic solvents, whereas those copolyimides with higher BTDA-4ODA content are only partially soluble or insoluble. However, all the copolyimides prepared can be compression molded. It has also been found that segmental motion above T_g is heavily suppressed in the BTDA-4ODA homopolymer relative to that in the BTDA-3DDS homopolymer. This reduction in molecular motion may severely hinder the solubility and fusibility of the BTDA-4ODA homopolymer. © 1993 John Wiley & Sons, Inc.