A convenient, low cost micro-patterning method using a new side group polymer containing phenolphthalein is reported. A random copolymer of t-BOC-protected phenolphthalein methacrylate (t-BMPP) with methyl methacrylate (MMA) was prepared by radical copolymerization in dioxane. The negative-tone patterns of this polymer could be obtained by photo-deprotection of the t-BOC groups due to the effect of dissolution inhibition by the phenolic group of the phenolphthalein. The chemical and optical properties of the polymer were, as anticipated, very close to those of the corresponding phenolphthalein and the pH controlled colorimetric transition was reproducibly observed. The contrast in solubility and chromism upon alkaline treatment makes this polymer a promising candidate for investigating spatially-directed chromism and selective deposition of pH sensitive polymers. SEM image of parallel lines of P(MMA/PPT) generated by contact UV exposure.