Fluorescence and solubilization studies of polymer—surfactant systems

Abstract

The interactions of sodium dodecyl sulfate (SDS) with cationic polymers have been investigated in this study using fluorescence-probe, dye-solubilization and solubility measurements. Information on the polarity of the SDS “micellar” microenvironment, in which the probes are solubilized, and the alterations in it in the presence of polymers have been obtained over a range of SDS concentrations. Dye-solubilization as well as fluorescence measurements indicate the existence of hydrophobic environments in the pre- and post-precipitation regions. Interestingly, these environments in the immediate vicinity of the precipitation region in the case of a cellulosic polymer (Polymer JR)—SDS system are much more hydrophobic than those in an acrylamide copolymer (Reten 220)—SDS system. A comparison of the solubilization capacity of polymer—surfactant aggregates in solution indicates the structure of the complexes on either side of the precipitation maximum to be different. The results obtained point to a hemi-micelle/inverse cylindrical micelle-type aggregate in the pre-precipitation zone and a conventional micelle-type structure beyond the point of maximum precipitation.