INFLUENCE OF THE POLYMER MOLECULAR-WEIGHT ON THE SURFACTANT-POLYMER INTERACTIONS - LIPFN-PVP AND SDS-PVP SYSTEMS

Surface tension, viscosity, density, and H-1-NMR measurements on lithi um heptadecafluorononanoate (LiPFN) aqueous solutions containing 1% po ly(vinylpyrrolidone) (PVP) at different molecular weights have been ca rried out. The results show the influence of the polymer molecular wei ght on the polymer-surfactant interaction and give information on the complex kinetic mechanism of the absorption of surfactant on polymer o ccurring through several steps. In particular the data show that, at l ow LiPFN concentration, the surfactant undergoes a phase transition fr om the molecular to the self-aggregated state. Such a kinetic step is not accompanied by conformational changes of the polymer. Increasing t he LiPFN concentration causes interactions between the fluorinated mic elles and the polymer to occur. The micelle-polymer interactions: invo lve selected regions of the polymer and thereafter the whole macromole cule. In such a process the PVP chains reorganize themselves around th e LiPFN micelles to give dressed micelles. Surface tension measurement s on sodium dodecyl sulfate (SDS) in PVP K30-water mixtures have also been carried out. Comparison of these data with those previously obtai ned on SDS-water-PVP K90 shows that the influence of polymer molecular weight on the polymer-surfactant interaction is not peculiar to perfl uorinated surfactants.