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 depende nt on the concentration of added Na(2)S0(4). The phase separation regi on in the presence of salt decreases with increasing temperature. Clea ring transition temperatures from the two-phase to the one-phase regio n are reported. Fluorescence measurements using pyrene as the luminesc ence probe, H-1 NMR spectra, and viscosity measurements show that the interaction between polymer and surfactant takes place also when no ph ase separation occurs. In systems with 3% polymer concentration this i nteraction leads to gel formation (but no phase separation) even in th e absence of salt.