Equilibrium swelling and pH-sensitivity of a polyelectrolyte copolymer hydrogel were controlled by employing copolymers with different hydrophilic-hydrophobic balances. Model pH-sensitive hydrogels, e.g., poly(methacrylic acid), poly(methacrylic acid-co-acrylamide), poly(methacrylic acid-co-2-hydroxyethylmethacrylate), poly(methacrylic acid-co-styrene) were synthesized at various monomer compositions. As hydrophobicity of the copolymer hydrogels increased, the equilibrium swelling decreased while the pH-sensitivity increased. In the case of poly(methacrylic acid-co-acrylamide), polymer-polymer interaction significantly affected the equilibrium swelling and provided a wide range control of pH-sensitivity.