Synthesis and Properties of Novel Melt Processable Isomeric Polythioetherimides

A series of 3,3 ’ ,4,4 ’ -diphenylthioethertetracarboxylic dianhydride (s-TDPA), 2,3,3 ’ ,4 ’ -diphenylthioethertetracarboxylic dianhydride (a-TDPA), and 2,2 ’ ,3,3 ’ -diphenylthioethertetracarboxylic dianhydride (i-TDPA) isomer mixtures were synthesized from 3- and 4-chlorophthalic anhydrides. Copolythioetherimides derived from TDPAs with different ratios of the isomers and 4,4 ’ -oxydianiline (ODA) were prepared by a two-step polycondensation procedure. Solubility, thermal properties, mechanical properties and melt processability of copolythioetherimides were investigated and compared with corresponding homopolyimides. The dependence of these properties on the composition of TDPA isomers and the effects of molecular structures were discussed in this work in order to obtain an indication for the molecular design of high performance melt-processable polyimides.