Hydrophobic core-hydrophilic shell graft block copolymers for unimolecular observation by AFM

Abstract

Graft block copolymers for unimolecular observation by AFM are designed considering polymer morphology and affinity to substrate. For the observation on hydrophilic mica substrate, graft block copolymers with hydrophobic polystyrene (PS) core-hydrophilic poly(2-vinylpyridine) (P2VP) shell are successfully synthesized via anionic grafting polymerization from lithiated poly(p-methylstyrene) (PpMS). Preparation of the graft block copolymers are achieved by adding 2VP monomer to the chain end active PpMS-g-PS. As a confirmation of synthesis, AFM measurement clearly shows the molecules having a worm like structure lying on mica. According to cross-sectional analysis, the AFM image would be explained by aggregated PS core and extended P2VP shell. This reveals that controlling morphology of graft block copolymers on the substrate is achieved by designing side chains using segment affinities to the substrate.