Mixtures of polyelectrolytes and oppositely charged surfactants are employed in a multitude of applications in e.g. paints, shampoos, water and soil treatment. In these applications they may, depending on total concentration and the concentration ratio of surfactant and polymer, act as stabilisers or destabilsers. The association in bulk between water-soluble highly charged cationic polyelectrolytes, with and without grafted hydrophobic side-chains, and anionic surfactant, SDS, were studied by employing turbidimetry and electrophoretic mobility measurements. The polyelectrolyte-surfactant complexes formed at low surfactant concentrations are positively charged. However, as the surfactant concentration is increased the complexes first become uncharged and at still higher concentrations, still well below the critical micellar concentration of the surfactant in pure water, the polyelectrolyte-surfactant complex becomes net negatively charged. The interactions between negatively charged surfaces precoated with polyelectrolytes were studied by means of surface force measurements, employing the interferometric surface force apparatus and atomic force microscopy. The effect of adding anionic surfactant on the interfacial properties were determined using a range of methods.
Triblok ethylene oxid - propylene oxid copolymerer med strukturen EOnPOmEOn kaldes poloxamer, og disse er både af stor teknisk og fundamental interesse. Copolymererne danner i vandige opløsninger forskellige typer miceller og geler afhængig af temperatur, koncentration, polymer sammensætning og tilstedeværelsen af eventuelle co-solutter. I dette foredrag vil jeg fokusere på betydningen af vands vekselvirkninger med polymerblokkene under micelledannelsen. En række metoder har været benyttet til at undersøge micelledannelsen af poloxamer samt faseadskillelse af PPO, og disse undersøgelser viser betydningen af hydrofobe vekselvirkninger mellem specielt PPO og vand. Forskellige modeller for micelledannelsen vil blive diskuteret og sammenlignet med resultater fra DSC og densitets målinger. Betydningen af polydispersitet på micelledannelsen vil blive illustreret og effekten af salte på termodynamiske ændringer ved micelledannelsen vil blive demonstreret. Poloxamer kan bruges som model systemer til at opnå en forståelse for hydrofobe effekters rolle i associations processer som for eksempel protein foldning.