Polyvinylacetal of 4-[2-(4-formylphenyl)ethenyl]pyridium(PVA-FEP) was synthesized and the layer by layer self-assembly from PVA-FEP as polycation with a series of polyanions was investigated. The multilayer utrathin films formed are photoreactive. Under UV irradiation the [2+2] cycloaddition of the styrylpiridium moieties of PVA-FEP takes place to produce crosslinking net works in the layers of the film. And the stability of the irradiated film toward polar solvents enhances greatly. The patterning of the film has been realized by selective UV exposure of the film through a photomask then developing in saturated sodium dodecyl sulfate aqueous solution.
