Molecular composites prepared by in situ direct synthesis of wholly aromatic rigid‐rod polyamides via the phosphorylation reaction in a dissolved nylon‐6 matrix

Abstract

Wholly aromatic rigid-rod polyamides such as poly(p-phenyleneterephthalamide) (PPD-T) were synthesized in situ in a solution of nylon-6 via the phosphorylation polycondensation method to form nanocomposites or so-called "molecular composites." The incorporation of PPD-T into a nylon-6 matrix was achieved by this approach in a more compatibilized form than that obtained by the conventional coagulation method that entails precipitation of a blend of PPD-T and nylon-6 in a solvent, for example, concentrated sulfuric acid. Gelation occurred during the synthesis, presumably because of the formation of interpenetrating networks accompanied by some block-copolymer formation. The transparency and tensile properties of the resultant composite films from the rigid-rod aromatic polyamide/nylon-6 combination were improved over those of nylon-6 film alone. Rainbow-colored intense birefringence was observed for the composite films under crossed polarizers. These properties are discussed in context with the in situ synthesized rigid-rod polyamides uniformly incorporated in nylon-6.