Synthesis and characterization of novel semiaromatic copolyamides bearing both polar hydroxyl and unsaturated allyl substituents

A series of novel semiaromatic (co)polyamides, poly(octylene terephthalamide)-ran-poly[octylene 2,5-bis(allyloxy)terephthalamide] (APA8T-x, x represents the molar fraction of allyloxy containing structure unit), were prepared via the interfacial polymerization of 1,8-diaminooctane, terephthaloyl chloride, and 2,5-bis(allyloxy)terephthaloyl chloride. The polymerization conditions were optimized in terms of the yields and the molecular weights of the resultant polymers. These polymers were converted to the target macromolecules, poly(octylene terephthalamide)-ran-poly[octylene (2,5-dihydroxy-3,6-diallyl)terephthalamide] (CRPA8T-x), through solid state Claisen rearrangement reaction, as characterized by ¹H NMR and FT-IR spectroscopies. While APA8T-x was only soluble in very limited solvents, the solubility of CRPA8T-x in polar solvents improved remarkably, especially for those with high counit content. Due to the polarity of hydroxyl group, CRPA8T-x showed an improved hydrophilicity than APA8T-x. The treatment of aramid fibers with CRPA8T-x, as sizing agents, enhanced obviously their interfacial adhesion toward epoxy resin. The fibers sized with 0.5 wt% CRPA8T-75 solution in the mixture of 1,1,2,2-tetrachloroethane and phenol (40:60, w/w) exhibited a maximum increase of 60% in interfacial shear strength than the naked fibers. The easy preparation and the facility for the further modification through the dual functional substituents may greatly widen the application of semiaromatic polyamides.