Systematic dielectric relaxation study of solid-like polyelectrolyte- surfactant complexes formed between poly(styrenesulfonate) and cationic surfactants

摘要

The dielectric relaxation behavior of polyelectrolyte-surfactant complexes with ordered lamellar microstructure were studied using broadband dielectric spectroscopy technique in the frequency range of 0.1 Hz to 2 MHz. We employed four complex samples formed between poly(styrenesulfonate) and didodecyldimethylammonium or alkyltrimethylammonium with various alkyl chain length. Three dielectric relaxation modes were observed in all complexes. The fastest and slowest relaxation modes showed Arrhenius temperature dependence. The fastest relaxation mode is attributed to motions of a surfactant grafted onto a polymer chain, whereas the slowest relaxation mode is attributed to the motions of an ion-pair formed between a negatively charged electrolyte monomer unit in a polymer and positively charged headgroup in a surfactant molecule. The intermediate relaxation mode showed Vogel-Fulcher-Tamman temperature dependence, and accordingly it derived from the segmental motion of the polymers forming intralamellar loops, interlamellar bridges or cilia. The slowest relaxation mode strongly correlates to the conductivity of the system, which indicates that surfactant ions are transported by the repetition process of formation and dissociation of ion-pairs.