Tailored rigid‐flexible block copolymers, 1. Synthesis of diblocks of poly(p‐benzamide) and poly(m‐phenylene isophthalamide)

Anilino‐terminated poly(m‐phenylene isophthalamide) [PhNH(MPD‐I)] and benzoyl terminated poly(p‐benzamide) [PhCO(PBA)] were coupled according to a one‐pot two‐step scheme of Yamazaki's reaction. Diblock copolymers with varying length of the flexible PhNH(MPD‐I) segment, and similar length of the rigid PhCO(PBA) block, were freed from unbound homopolymers exploiting their selective solubility in N,N‐dimethylacetamide (DMAc) containing varying amounts of LiCl. The method should also allow a fractionation of the compositional distribution of the copolymers. Copolymers were characterized by 1H NMR spectroscopy, thermal analysis and intrinsic viscosity. In an aggregating solvent the viscosity appears to decrease with the length of the flexible block.