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

Thermodynamic and kinetic studies of the binding of cationic surfactan t molecules (N-alkylpyridinium chloride: C(n)PyCl, n = 4, 8, 10, 12, 1 6, 18) to an anionic polymer network (poly(2-(acrylamido)-2-methylprop anesulfonic acid): PAMPS) over a wide range of concentrations and ioni c strengths have been made, and the binding constant K and the coopera tivity parameter u are calculated. These parameters increase with incr easing alkyl chain length, indicating the binding is cooperative in na ture and dominated by a hydrophobic interaction. The role of electrost atic and hydrophobic interactions in the initiating and propagating bi nding processes in the polymer network are discussed. The chemomechani cal contractile profiles of PAMPS gel could be explained in terms of t hese binding parameters and diffusion parameters in the polymer networ k.