BEHAVIOR OF FILMS OF REGENERATED CELLULOSE IN STRONGLY ALKALINE ENVIRONMENTS - ESTIMATION OF NONHOMOGENEITY FROM IONIC CONDUCTANCE

Membrane conductance and other data have been analysed to evaluate the tortuosity factor, theta, from considerations of anionic mobilities w ithin a regenerated cellulose film immersed in KOH solutions. Applicat ion of the equation theta = (1 + V(p))/(1 - V(p)), where V(p) is the v olume fraction occupied by the gel framework in an homogeneous gel, in dicated mobilities which were too high by 30-40%. It is proposed that these discrepancies arose from heterogeneity in the film due to the pr esence of a fraction xBAR of non-ionically conducting, crystalline par ticles of cellulose. In the range of 0-3 mol dm-3 KOH xBAR was approxi mately 0.32 in good agreement with the value of 0.36 determined from e quilibrium ion-exchange measurements. xBAR decreased to ca. 0.1 in 5.3 mol dm-3 KOH owing to ionisation and swelling of initially crystallin e regions. Between 5.3 and 7 mol dm-3 KOH xBAR showed an increase to c a. 0.35: this deduction is consistent with the formation of a new crys talline phase, potassium cellulose II. At KOH concentrations above 7 m ol dm-3 there was an apparent decrease in xBAR, probably related to th e ionisation of secondary alcohol groups.