Résumé
When telechelic polymers (poly-ethyleneoxide grafted at both ends with an aliphatic chain) are added to a microemulsion of decane droplets in water stabilized by a surfactant film they can link the droplets and thus introduce an effective attractive interaction between the droplets, eventually leading to a phase separation. Starting from a neutral microemulsion we show that this attractive interaction can be offset by adding minute quantities of an ionic surfactant, thus introducing a repulsive Coulombic interaction. This opens up the possibility of 'weighting' an unknown effective attraction against a well known repulsion. The phase behaviour and the small angle neutron scattering spectra of different samples illustrate this point. The spectra are simulated assuming the interaction potentials to be the sum of attractive and repulsive contributions and a good agreement is found between the experimental and simulated spectra in the neutral microemulsion, in the charged microemulsion and in the charged and connected microemulsion.