Photochemical fixation of structures in binary polymer brushes-influence of layer thickness and grafting method

Polymer brushes consisting of hydrophilic and hydrophobic polymer components (poly-4-vinylpyridine, polymethacrylic acid and polystyrene, respectively) change their surface properties (as revealed by contact angles) when they are exposed to various solvents. In brushes prepared via grafting-from methods (using a specific surface initiator) layer thicknesses up to 300 nm were obtained. Copolymerization of the brush component monomers with 2-(4'-styryl)-indene yielded photo-cross-linkable brushes, which were used to fix the brushes in either the hydrophilic or hydrophobic state. Structural patterns differing in surface properties were produced and fixed by photo-cross-linking the hydrophobic component in that samples were irradiated through a mask. The patterns turned out most stable in moderately thick layers. AFM pictures confirm the contact angle results but reveal micro-domains of the two immiscible polymers in the grafted layers.