Synthesis of high‐molecular‐weight rodlike polyamides and block copolymers

Abstract High‐molecular‐weight polyamides containing p ‐benzamide units can be obtained by polycondensation of monomers having preformed amide linkages in N ‐methylpyrrolidone with added CaCl 2 and LiCl in the presence of pyridine and triphenylphosphite (the conditions used by Higashi et al.). For example, the polyterephthalamide of 4,4′‐diaminobenzanilide having η inh = 5.4 was obtained. Similarly, polycondensation of p ‐phenylenediamine with N , N ′‐ bis ( p ‐carboxyhenyl)terephalamide produced a polymer having η inh = 5.15. These results constitute the first demonstration that the phosphorylation reaction can be used to prepare rodlike polymers containing p ‐benzamide units of molecular weights adequate for commercial‐quality fibers. Polymerization of p ‐aminobenzoic acid using either Yamazaki or Higashi conditions does not lead to a polyamide having a high inherent viscosity. Block copolyamides having rigid and semiflexible blocks were prepared by using both Yamazaki and Higashi conditions. Block copolymers composed of p ‐ and m ‐benzamide units, and having η inh = 3.0–3.1, were synthesized by using a rigid prepolymer obtained by applying the Yamazaki reaction to a monomer containing a preformed amide linkage, 4‐ N ‐(4′‐aminobenzamido)‐benzoic acid. Use of monomers having preformed amide linkages with Higashi conditions afforded block copolymers having inherent viscosities of up to 4.75.