Photo-control of adhesion properties by detachment of the outermost layer in layer-by-layer assembled multilayer films of Preyssler-type polyoxometalate and polyethyleneimine

The ability to generate small-scale structures and assemble functional substances in the fields of micro electronics and optoelectronics continues to support advances in information technology. Here we present a novel type of layer-by-layer assembled films, whose surface properties can be controlled by UV irradiation in aqueous solution. We have designed a photochromic multilayer film of Preyssler-type polyoxometalate (NaP5W30) and polyethyleneimine (PEI) by using the layer-by-layer method. We found that the outermost PEI layer could be detached by UV irradiation in aqueous solution, and that this process could then cause inversion of the zeta potential. Furthermore, we achieved reversible-control of the surface properties first by UV irradiation, which induced the detachment of the outermost PEI layer, and by subsequent dipping into a PEI solution, which attached a new PEI layer. Finally, we successfully prepared photopatterned films with highly site-selective adsorption abilities by image-wise UV exposure.