Summary: The synthesis of a series of rod-coil diblock copolymers with flexible poly(ethylene oxide) chains ( = 5 000 g · mol−1) and rod blocks consisting of monodisperse oligo(p-benzamide)s is described. The formation of defined supramolecular aggregates in solution as well as the solid state has been analyzed. The length of the oligo(p-benzamide)s has been systematically varied from n = 1 to 7 units. The influence of n on aggregation in chloroform and aqueous solution was investigated by GPC as well as UV-vis spectroscopy. A critical aggregation length was found for chloroform (n = 5) and water (n = 4), below which no aggregation is observed under otherwise identical experimental conditions. Aggregation of the polymers in chloroform solution can be chemically reversed by the addition of PCl5, resulting in conversion of the aromatic amides into imidoyl chlorides. Such amide-protected block copolymers show no aggregation in NMR and GPC experiments. Imidoyl chloride formation was shown to be reversible, i.e., addition of water regenerated the oligo(p-benzamide) blocks.
Conversion of aramide block copolymer into molecularly dissolved form using PCl5.