A series of quinoline-labeled water-soluble copolymers, synthesized through free radical copolymerization of vinyl modified quinoline derivatives with water-soluble monomers such as the nonionic N,N-dimethylacrylamide (DMAM), the anionic sodium 2-acrylamiclomethylpropanesulfonate (AMPSNa), and the cationic methacrylamidopropyltrimethylammonium chloride (MAPTAC), are investigated in the present work. As a result of the protonization/deprotonization equilibrium of the quinoline unit, the optical properties (absorption and, more important, emission of light) of these copolymers are controlled by the pH of the surrounding environment. In fact, the emitted light of the quinoline group changes from blue to green upon decreasing pH. It is shown that this pH-controlled color change can be tuned by the nature of the polymer chain (anionic, nonionic, or cationic) or the existence of substituents (such as cyanophenyl or perfluorophenyl groups), giving rise to a library of pH-responding quinoline-labeled materials that cover almost the entire acidic pH region.