PHASE-BEHAVIOR, MICROSTRUCTURE, AND DYNAMICS IN A NONIONIC MICROEMULSION ON ADDITION OF HYDROPHOBICALLY END-CAPPED POLY(ETHYLENE OXIDE)

We report on the effects on the phase behavior, microstructure, and rh eology in the water-rich part of the ternary nonionic surfactant syste m comprising pentaethylene glycol dodecyl ether (C12E5)-water-decane, on addition of poly(ethylene oxide) (PEG) and hydrophobically end-capp ed PEO (HM-PEO). The two polymers destabilize both the micellar and th e lamellar phases. With PEO, a segregative phase separation is observe d, while with HM-PEO, an associative phase separation is seen. The mic ellar phase containing HM-PEO was investigated by NMR relaxation and s elf-diffusion measurements and small-angle neutron scattering as well as low shear viscosity and oscillatory frequency sweep measurements. I t was found that the polymer affected the intermicellar interaction, l eading to an increased ordering of the micelles, while leaving the mic ellar size unchanged. Addition of HM-PEO (less than or equal to 2 wt R i led to a drastic decrease of the micellar self-diffusion coefficient and additionally to an increase of the low shear viscosity by several orders of magnitude. The storage and loss moduli were successfully fi tted to a single Maxwell element. Analysis of the fitted parameters an d comparison with percolation theory yielded the fraction of polymers that interconnected the micelles (thus forming bridges) as well as the fraction of polymers that did not contribute to the connectivity of t he network (resulting in loops).