The Effect of the Substitution Position of Nitrogen Atoms on Copolyimide Properties

Two containing nitrogen diamine monomer, 2-(4-aminophenyl)-5-aminopyrimidine (PAPRM) and 2,5-two(dimethyl amino methylene)-1,4-((paraamino) phenyl)benzene(DMAPB), was synthesized. The corresponding copolyimide containing 40–80 mol % PAPRM and DMAPB were prepared. The copolymers showed excellent solubility and good film-forming capability. Most of the SPI membranes were both tough and flexible and thermally stable up to 330 °C.With increasing content of the nitrogen atoms, water uptake of membranes and dimensional changes also remarkable decrease. Compared with the main chains containing nitrogen atoms, the side chains type displayed excellent water stability and good mechanical properties.