Self-Assembly and Photoinduced Optical Anisotropy in Dendronized Supramolecular Azopolymers

Herein we report the preparation and characterization of dendronized supramolecular polymers composed of a carboxy-terminated azodendron, dAZO, and two different vinylpyridine-containing polymers: poly(4-vinylpyridine) (P4VP) and polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer. P4VP can selectively complex dAZO through hydrogen-bonding interactions, thus resulting in liquid crystalline materials. Additionally, this strategy is also applicable to the preparation of dendronized supramolecular block copolymers (BCs). Lamellar, cylindrical, and spherical morphologies are observed for the BC complexes depending on the dAZO to vinylpyridine repeating unit ratio. Photoinduced orientation of the azobenzene moieties is obtained in films of the H-bonded materials-both P4VP and PS-b-P4VP based complexes-by using 488 nm linearly polarized light and characterized through birefringence and dichroism measurements. High and, stable values of birefringence are obtained for polymers with azobenzene content as low as 2.7 wt %, thus demonstrating the benefits of preorganization in photoactive dendritic moieties in side-chain H-bonded materials.