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

The permselective and non-permselective behaviour of poly(vinylferrocene) (PVF) films has been studied potentiometrically and with the dual quartz crystal 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 NDS2- 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 NDS2- 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.