EFFECTS OF TEMPERATURE, SURFACTANT CONCENTRATION, AND SALINITY OF THEDYNAMICS OF DILUTE-SOLUTIONS OF A NONIONIC CELLULOSE DERIVATIVE

The interaction between sodium dodecyl sulfate (SDS) and ethyl(hydroxy ethyl)cellulose (EHEC) has been studied as a function of temperature i n dilute aqueous solutions in the presence of various amounts of SDS a nd at some different levels of NaCl addition with the aid of dynamic l ight scattering (DLS). The DLS results suggest initially an exponentia l decay followed by a stretched exponential at longer times. The fast mode is always diffusive, and the results are presented in terms of th e hydrodynamic radius. The slow mode exhibits a stronger and more comp lex wave vector dependence than the fast mode. The interaction between the polymer and surfactant gives rise to the formation of polymer-sur factant clusters at low levels of surfactant addition. The cluster siz e increases at low surfactant concentrations and passes through a maxi mum slightly above the critical aggregation concentration. In this pro cess, the interplay between swelling and deaggregation of the clusters plays an important role. The position of the maximum is shifted towar d lower SDS concentrations with increasing temperature. At low levels of surfactant addition, the growth of the aggregates is promoted by in creasing temperature and salinity. As the surfactant concentration inc reases, the aggregates gradually become disrupted and the impact of te mperature and salinity on the size of the polymer aggregates becomes s mall.