The binding of sodium dodecyl sulfate (SDS) to six random nonionic copolymers with the general chemical name polyvinyl(methyl imidazole-co-pyrrolidone-co-acrylate) were studied using electromotive force measurements (EMF) and isothermal titration calorimetry (ITC). In terms of their composition expressed in mole percent, each polymer contains 45 mol % methyl vinyl imidazole (MVI), 45 mol % vinyl pyrrolidone (VP)1 and 10 mol % of each of six different substituted acrylates. The purpose of the work was to investigate how subtle structural changes in the acrylate monomer affect the binding properties of SDS. The results showed significant differences in the binding behavior of the polymers, which are reflected in the determination of critical constants associated with SDS binding, like binding isotherms, the degree of sodium ion association to the bound SDS micelles, and the binding enthalpies as measured by ITC, especially in the early stages of binding. This opens the possibility of using ITC and EMF experiments which effectively measure the binding process as a mean of monitoring and characterizing subtle differences in structurally related macromolecules.

The interaction between the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) and the Pluronic triblock copolymer F127 was investigated. F127 is a nonionic surfactant with structural formula EO97PO69EO97, where EO represents the ethylene oxide block and PO represents the propylene oxide block. A combination of experiments involving a TTAB selective electrode (electromotive force), isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), and light scattering have shown that TTAB binds to both monomeric and micellar F127. TTAB forms a polymer/micellar TTAB complex with monomeric F127. In addition, TTAB binds to F127 micelles leading to the transformation of the aggregated F127 into mixed micelles followed by a breakdown of these aggregates into smaller mixed F127/TTAB aggregates as more TTAB is added. This process continues until all the aggregated F127 is dissociated. DSC measurements have also shown that small amounts of TTAB (typically 10(-4) mol dm(-3)) can decrease the critical micelle temperature (cmt) of F127. This represents a third mode of binding in which TTAB induces F127 to form micelles at temperatures several degrees below its "pure" cmt. Possible mechanisms for these processes involving different modes of interaction of TTAB with F127 are introduced and discussed.

Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) measurements were carried out on various binary mixtures of the nonionic surfactant hexaethylene glycol mono-n-dodecyl ether (C12EO6) and the triblock copolymer "Pluronic" F127 of chemical composition EO97PO69EO97, which is a polymeric nonionic surfactant (EO represents the poly(ethylene oxide) blocks and PO the polypropylene oxide blocks). In all cases mixed micellar aggregates were formed and critical micellar concentrations (cmc's) of binary mixtures containing different mole fractions of the surfactants were measured using ITC. The interaction between the two surfactants shows synergistic behavior. The results were analyzed using a regular solution theory, which introduces a special parameter to characterize the interaction between two surfactant species in a mixed micelle. The cmc's of the F127-rich micelles were also characterized with DSC.

Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) measurements were carried out on various binary mixtures of the nonionic surfactant hexaethylene glycol mono-n-dodecyl ether (C12EO6) and the triblock copolymer “Pluronic” F127 of chemical composition EO97PO69EO97, which is a polymeric nonionic surfactant (EO represents the poly(ethylene oxide) blocks and PO the polypropylene oxide blocks). In all cases mixed micellar aggregates were formed and critical micellar concentrations (cmc's) of binary mixtures containing different mole fractions of the surfactants were measured using ITC. The interaction between the two surfactants shows synergistic behavior. The results were analyzed using a regular solution theory, which introduces a special parameter to characterize the interaction between two surfactant species in a mixed micelle. The cmc's of the F127-rich micelles were also characterized with DSC.

The polymer-surfactant complex formed between sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) contains SDS micelles bound to the polymer chain. When a PVP sample of MW 360 000 is saturated with SDS micelles, the complex is a beadlike structure with the PVP wrapped around 25 SDS micelles. The bound SDS was systematically removed from the polymer chain by the addition of the nonionic surfactant hexaethylene glycol mono-n-dodecyl ether, C12EO6, and this process was monitored using isothermal titration calorimetry (ITC). Electromotive force, emf, measurements carried out with a dodecyl sulfate electrode were also used to monitor the desorption of bound SDS from the polymer chain via the SDS monomer concentration. Furthermore, these measurements showed that during the removal of SDS from the polymer, mixed SDS/C12EO6 micelles were formed both on the polymer chain and in solution. The structure and composition of these mixed micelles were determined using small-angle neutron scattering (SANS). The data indicate that electrostatic interactions are the main factor influencing the binding.