ASSOCIATIVE PHASE-SEPARATION OBSERVED IN A HYDROPHOBICALLY-MODIFIED POLY(ACRYLAMIDE)/SODIUM DODECYL-SULFATE SYSTEM

Experimental evidence has been found for associative phase separation in a mixture of a nonclouding hydrophobically modified poly(acrylamide) and sodium dodecyl sulfate. The phase separation is strongly dependent on the concentration of added Na(2)S0(4). The phase separation region in the presence of salt decreases with increasing temperature. Clearing transition temperatures from the two-phase to the one-phase region are reported. Fluorescence measurements using pyrene as the luminescence probe, H-1 NMR spectra, and viscosity measurements show that the interaction between polymer and surfactant takes place also when no phase separation occurs. In systems with 3% polymer concentration this interaction leads to gel formation (but no phase separation) even in the absence of salt.