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The system hydroxypropyl methyl cellulose (HPMC)/sodium dodecyl sulfate (SDSVwater has been investigated over an extended composition interval from infinite dilution to a polymer concentration above the critical overlap concentration (c*) and a surfactant concentration up to ~3 times the normal critical micelle concentration (cmc). The aim has been to characterize the redistribution (adsorption) of surfactant to the polymer and to investigate the system properties as a function of this adsorption. Several methods such as viscometry, equilibrium dialysis, cloud point determinations, dye solubilization, and fluorescence spectroscopy have been utilized. The onset of adsorption begins at ~4.3 mM, and then it increases as an increasingly cooperative phenomenon to a saturation maximum in a region below the normal cmc (~8 mM). This maximum approaches the normal cmc as the polymer concentration approaches zero. SDS adsorbs in a cooperative manner in the form of clusters, the average aggregation number (N) of which decreases with decreasing polymer concentration from -50 for 0.2% HPMC to 20-25 at infinite dilution. The solubilization capacity of the HPMC/SDS/water system is somewhat less than previously reported for the ethyl hydroxyethyl cellulose/SDS/water system. Important rheological effects (high viscosity) are observed in a fairly limited composition range beginning at the onset of adsorption and ending long before adsorption saturation is reached. The maximum capacity of adsorption averaged over the entire polymer chain is found to be of the order of one adsorbed amphiphile molecule per polymer monomer unit.

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