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RESEARCH PRODUCT

Rod-Length Dependent Aggregation in a Series of Oligo(p-benzamide)-Block-Poly(ethylene glycol) Rod-Coil Copolymers

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The synthesis of a series of rod-coil diblock copolymers with flexible poly(ethylene oxide) chains (M n = 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 PCl 5 , 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.