Microemulsion efficiency boosting and the complementary effect. 1. Structural properties.
Amphiphilic diblock copolymers added to microemulsions proved to enhance the efficiency of surfactants dramatically. The complementary effect of homopolymers is considered in the current work. A possible application of the homopolymer addition could be the viscosity tuning of the microemulsion without changing the considered bicontinuous phase. Furthermore, (homo)polymers are added for many other reasons in technical applications. A theory by Eisenriegler predicts a decreased efficiency when homopolymers are added. In further experiments, the simultaneous addition of homopolymers and diblock copolymers probes whether the two opposite effects superpose and allow for a compensation. Then, efficiency and viscosity are adjustable independently. Experimentally, phase diagrams are investigated and the microscopic structure is measured by small-angle neutron scattering. Within the presented models, both experimental methods are compared and discussed on the basis of the surfactant membrane bending moduli. The homopolymer effect is about 7 times larger than that theoretically predicted, and the superposition of the two polymer effects allows for a compensation with an optionally tunable viscosity.