EQCM studies of poly(vinylferrocene) in 1,5-naphthalenedisulfonate disodium salt bathing solutions

Abstract

The permselective and non-permselective behaviour of poly(vinylferrocene)(PVF) films has been studied potentiometrically and with the dual quartzcrystal microbalance (DQCM) in disodium naphthalene disulfonate(Na₂NDS) solutions. Potentiometry shows that PVF films are permselective in Na₂NDS bathing solutions having concentrations less than 48 mM. The open-circuit potential results show that both NDS^2- and (NaNDS)^- populate the oxidized film between the concentrations of 48 and 250 mM Na₂NDS. The molar mass data obtained using slow-scan potential-sweep experiments confirm the conclusions regarding ion transfers reached using potentiometry. Specifically, the oxidation of the PVF films in the 8 to 64 mM Na₂NDS bathing solutions yielded experimental molar masses that showed the films were permselective. Additionally, the gravimetric data provided information on neutral species transfer: between 8 and 11 water molecules per charge centre entered each film upon PVF oxidation. The molar mass data also support the finding that a mixture of NDS^2- and (NaNDS)^- enter the films upon oxidation in the concentration range between 64 and 250 mM. Open-circuit DQCM measurements, both with 100% reduced films and with 100% oxidized films, showed that salt entered the film at concentrations greater than 64 mM Na₂NDS.