EFFECTS OF HYDROPHOBIC INTERACTION ON THE COOPERATIVE BINDING OF A SURFACTANT TO A POLYMER NETWORK

Thermodynamic and kinetic studies of the binding of cationic surfactant molecules (N-alkylpyridinium chloride: C(n)PyCl, n = 4, 8, 10, 12, 16, 18) to an anionic polymer network (poly(2-(acrylamido)-2-methylpropanesulfonic acid): PAMPS) over a wide range of concentrations and ionic strengths have been made, and the binding constant K and the cooperativity parameter u are calculated. These parameters increase with increasing alkyl chain length, indicating the binding is cooperative in nature and dominated by a hydrophobic interaction. The role of electrostatic and hydrophobic interactions in the initiating and propagating binding processes in the polymer network are discussed. The chemomechanical contractile profiles of PAMPS gel could be explained in terms of these binding parameters and diffusion parameters in the polymer network.