Preparation and dielectric properties of porous cyanoethyl cellulose membranes

Cyanoethyl cellulose (CEC) with a high degree of substitution of cyanoethyl group was synthesized by using the Michael addition reaction. Porous CEC membranes were successfully prepared by the non-solvent induced phase separation method. The parameters that influence the morphology and properties of the CEC membranes were investigated and discussed. Asymmetric membranes with higher porosity were obtained when water was used for the coagulation bath. On the other hand, dense symmetric CEC membranes with cellular or flat pores were obtained when ethanol or DMF/H2O was used for the coagulation bath. The porosity of the CEC membranes was reduced with increased polymer concentration in the CEC/DMF solutions. Moreover, the morphology of CEC membranes also depended on the molecular weight of CEC. In the case of using water as the coagulation bath, the morphology of the CEC membranes changed from an asymmetric structure with dense thin skin layer to a stick-like intertwined symmetric structure. When ethanol or DMF/H2O was used for the coagulation bath, the morphology of the resultant symmetric CEC membranes changed from cellular or flat pores to stick-like intertwined structure. The dielectric constant of the CEC membranes increased with a decrease in the porosity of CEC membranes.