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Siegel der Universität
Department für Chemie - Arbeitsgruppe Prof. Strey

Technically relevant amphiphile Blockcopolymers in Microemulsions

Julie-Laure Tchekountieu Mboumi, 2008

 

Almost 10 years ago it has been found that the addition of small amounts of amphiphilic block copolymers to mixtures of water, oil and surfactant induces several highly interesting effects. The most important one is an enormous increase of surfactant efficiency, i.e. solubilization capacity. Efficiency increases by factors of 10-20 are easily achieved. The diblock copolymers used were monodisperse model structures of the type poly(ethylenepropylene)-co-poly(ethyleneoxide). However, having in mind the utilization of this effect in technical applications commercially available and reasonably priced amphiphilic block copolymers are needed. In this study, the effect of the easily producible diblock copolymers of the type poly(alkyleneoxide)-co-poly(ethyleneoxide) (PAOx-PEOy), as well as the commercially available and widely-used triblock copolymers Pluronic® on balanced microemulsions is examined systematically. It will be shown that the addition of all PAOx-PEOy copolymers studied increases the surfactant efficiency. Adding the polymer poly(butyleneoxide)-co-poly(ethyleneoxide) the strongest efficiency increase is found, while the presumably more amphiphilic polymer poly(octyleneoxide)-co-poly(ethyleneoxide) leads to a smaller increase of efficiency. Furthermore the PAOx-PEOy copolymers cause an unexpected trend of the phase inversion temperature. Using triblock copolymers Pluronic®, the size and the sequence of the ethylene oxide and propylene oxide blocks determines whether a boosting or an anti-boosting of the solubilization efficiency is found. Systematic investigations of many microemulsion systems with variation of both, the polar and the nonpolar component as well as the surfactant provide evidence that the enormous increase in efficiency can be found in a large variety of pure and technical grade microemulsion systems and thus is based on a universal mechanism.