Effects on membrane properties of NaCS–PDMDAAC capsules by adding inorganic salts

Abstract: Inorganic salts were introduced into the formation process in the preparation of sodium cellulose sulfate (NaCS)–polydimethyldiallylammonium chloride (PDMDAAC) capsules in an effort to change the NaCS–PDMDAAC capsules properties. Membrane thickness of the capsules increased greatly, especially at higher salt concentrations, while network density of the capsules membrane exhibited the opposite effect. The size of the capsules remained unchanged; however, they were affected by the aforementioned two intrinsic capsules characteristics. The molecular weight cut-off (MWCO) of the capsules was increased in the presence of the salts, while the permeability of the whole capsules decreased. The mechanical strength increased at the lower salt concentrations while a decrease was exhibited at the higher salt concentrations. The ion order necessary for the increase in mechanical strength of the capsules was Mg2+ >Ca2+ >Na+ >K+ for cations and Cl− >SO4 2− for anions, which was inversely proportional to the ion radii. It was found that the properties of NaCS–PDMDAAC membranes could be controlled by merely making adjustments in the concentration of inorganic salts in the process. [Copyright &y& Elsevier]