Acrylamide (AM)/acrylic acid (AA) copolymers and AM/AA/N-(4-hexylphenyl)acrylamide (HPAM, 0.5 mol %) terpolymers with varied AA content have been synthesized by micellar copolymerization. Co- and terpolymers with 5-37 mol % AA and similar hydrodynamic volumes were prepared. Solution viscosity studies of the copolymers as a function of pH and copolymer concentration in deionized water and NaCl solution indicate normal polyelectrolyte behavior. In aqueous solutions, intra- or intermolecular hydrophobic associations may be favored by variation of terpolymer composition. Three-dimensional plots of both I-3/I-1 (from pyrene probe fluorescence) and viscosity as functions of pH and terpolymer concentration demonstrate the responsive nature of associations in water and in 0.5 M NaCl. Terpolymers containing approximately 9 and 21 mol % AA exhibit intermolecular (open) associations at less than or equal to pH 5 and in the presence of NaCl. The terpolymer containing approximately 37 mol % AA, however, exhibits no intermolecular associations in deionized water even at low pH. Pyrene fluorescence studies of this terpolymer indicate a significantly apolar environment-sensed by the probe at pH 4, suggesting that intramolecular (closed) microdomains are formed. Conceptual models based on hydrophobic, ionic, and hydrogen-bonding interactions in these systems are presented.