On the binding of sodium dodecylsulphate with poly(N-vinyl-2-pyrrolidone)

Abstract

The binding of sodium dodecylsulphate with poly(N-vinyl-2-pyrrolidone)(PVP) has been investigated at 303.15 K on the basis of equilibrium dialysis, surface tension, viscosity and apparent molar volume measurements. The data obtained suggest that in the presence of PVP, SDS exists as a monomer in dilute solutions (below 3 m<em>M</em>) while at a concentration of 3.4 m<em>M </em>it forms SDS anion "associates" which bind to the N^δ+ end of PVP. This initiates the unfolding of PVP coils; the process is almost completed at SDS concentration of about 10 m<em>M. </em>Further increase in the concentration of SDS causes not only the formation of "associates" of larger order (or even free micelles) but also mixed micelles. The equilibrium dialysis data have further been analysed in terms of various models of polymer-surfactant binding. The study reveals that SOS does form low order "anion associates" containing 2 or 3 SDS anions.