Synthesis and characteristics of novel copolymers bearing both acid amplifier and acid-sensitive units are described. The acid amplifier units in the polymer side chains were acidolytically transformed to sulfonic acid residues, leading to the deprotection of the acidlabile tert-butyl ester side chains introduced as a comonomer unit. The copolymer was 3.2 times more sensitive than poly(tert-butyl methacrylate) in the presence of a photoacid generator and, therefore, provides practical applicability for photoimaging.