Soluble and curable poly(phthalazinone ether amide)s with terminal cyano groups and their crosslinking to heat resistant resin

Soluble and curable aromatic polyamides have great potential use as processable and heat-resistant polymeric materials. In this study, a novel series of soluble aromatic polyamides (CN-PPAs) containing phthalazinone moiety and crosslinkable terminal cyano groups were synthesized by polycondensation of 1,2-dihydro-2-(4-carboxyphenyl)-4-[4-(4-carboxyphenoxyl)phenyl]-phthalazinone (DHPZ-DC) with calculated 4,4′-oxydianiline (ODA), followed by end-capping with 4-cyanobenzoic acid (CBA). Thermal crosslinking of CN-PPAs, catalyzed by zinc chloride, was then performed in the presence of terephthalonitrile (TPH) via heating either their films or powders up to 300-340 °C. The uncured synthesized polymers have good solubility while the cured samples become insoluble in common organic solvents. Spectra and elemental analysis measurements demonstrate cyclization reaction of terminal cyano groups to form s-triazine rings. The presence of TPH and ZnCl2 is effective in promoting thermal crosslinking and s-triazine forming reaction of the CN-PPAs under normal pressure. The resulting cured samples exhibit no Tg up to 400 °C by DSC and have excellent thermal stability. This kind of cyano-terminated poly(phthalazinone ether amide) may be a good candidate as matrix for high performance polymeric materials.