Abstract: The self-assembly of hydrophobically associating polyacrylamide (HAPAM) and the effect of adding gemini surfactant (dimyristic acid glycol ester di(α-sodium sulfonate), DMES-14) were studied by static light scattering, dynamic light scattering, and fluorometry. HAPAM formed hydrophobic microdomains in solution through self-assembly, which decreased the fluorescence intensity ratio (I₁/I₃) of the first peak (373 nm) and the third peak (383 nm) in the emission spectrum of pyrene as the polymer HAPAM concentration (C_P) was increased until a plateau was reached at high C_P. When surfactant was added to the polymer solution, the interaction between HAPAM and surfactant resulted in the formation of mixed micelles. This caused I₁/I₃ to decrease as the surfactant concentration (C_S) was increased at the same polymer concentration until C_S was greater than 30 mg·L^-1, after which point I₁/I₃ showed little change. The aggregation number of aggregates in the mixed system containing surfactant and polymer decreased at first and then increased as C_P was increased. A certain amount of surfactant could enhance interchain interactions, while excess surfactant broke down interchain interactions between the hydrophobic groups of HAPAM, which resulted in maximum values of the apparent weight average molecular weight (M_w,a), root-mean-square radius of gyration (<R_g>), and hydrodynamic radius (<R_h>) of HAPAM as C_S was increased. <R_g>/<R_h> increased slowly as C_S was increased, which reflected the relative stretch of the polymer chains.

Key words: Hydrophobically associating polyacrylamide, Gemini surfactant, Fluorescence spectrum, Aggregation number, Laser light scattering