To achieve easy spin coating and enhanced efficiency in the photolithographic process for the direct photochemical modification of surface, we incorporated photoacid generator WAG) into polymer backbone. Bis-(4-hydroxy-phenyl)-(4-methoxy-3,5-dimethyl-phenyl)-sulfonium chloride was synthesized as a monomer, and was polymerized with sebacoyl chloride and terephthaloyl chloride. The resulting polymeric PAG in chloride salt form was converted to the p-toluenesulfonate and 1-naphthol-5-sulfonate forms with ion-exchange reactions. By the photolithographic process with the polymeric PAG, the protecting groups of the linker molecules self-assembled onto a glass plate were micropatterned to produce an amine pattern for the microarray of oligonucleotides. The acids generated from the polymeric PAG effectively deprotect the acid-labile protecting groups of the linker molecules through a chemical amplification process in the exposed region. After the treatment of the patterned amino groups with a fluorescent dye, the pattern profiles were observed with a fluorescence scanner. The fluorescence image reveals a well-defined pattern at a micro level, which clearly indicates that the polymeric PAGs have a great potential in photochemical surface modification for the microarray of oligonucleotides. Copyright (c) 2007 John Wiley & Sons, Ltd.