Dielectric spectroscopy and micellization of aqueous solutions p-isononylphenoloxyethyleneglycolether

Dielectric relaxation spectra of optically isotropic aqueous solutions of p-isononylphenoldecaglycolether (NOP-10) were measured at 1.1 MHz, 9.376 GHz, 37.5 GHz from 275 to 313 K. The data were described assuming three Debye dispersion regions. Hydration numbers of NOP-10 molecules were calculated from an amplitude of the second dispersion region. Static permittivity values of the solutions were analyzed using theories for heterogeneous systems, and it was concluded that spheroidal micelles formed in the solutions at all investigated conditions. The shape of the micelles changed from prolate spheroids to spheres and then to oblate spheroids in the solutions with 9.97, 20, 30 wt% of NOP-10 in the temperature range from 275 to 313 K. A study of solutions with lower content of NOP-10 (1.14 and 4.97 wt%) have been made from 275 to 351 K, and it was deduced that in this case spherical micelles transformed to oblate spheroids and then to discs.