Effect of Ionic Radius in Metal Nitrate on Pore Generation of Cellulose Acetate in Polymer Nanocomposite

Abstract

To prepare a porous cellulose acetate (CA) for application as a battery separator, Cd(NO3)(2)4H(2)O was utilized with water-pressure as an external physical force. When the CA was complexed with Cd(NO3)(2)4H(2)O and exposed to external water-pressure, the water-flux through the CA was observed, indicating the generation of pores in the polymer. Furthermore, as the hydraulic pressure increased, the water-flux increased proportionally, indicating the possibility of control for the porosity and pore size. Surprisingly, the value above 250 LMH (L/m(2)h) observed at the ratio of 1:0.35 (mole ratio of CA: Cd(NO3)(2)4H(2)O) was of higher flux than those of CA/other metal nitrate salts (Ni(NO3)(2) and Mg(NO3)(2)) complexes. The higher value indicated that the larger and abundant pores were generated in the cellulose acetate at the same water-pressure. Thus, it could be thought that the Cd(NO3)(2)4H(2)O salt played a role as a stronger plasticizer than the other metal nitrate salts such as Ni(NO3)(2) and Mg(NO3)(2). These results were attributable to the fact that the atomic radius and ionic radius of the Cd were largest among the three elements, resulting in the relatively larger Cd of the Cd(NO3)(2) that could easily be dissociated into cations and NO3- ions. As a result, the free NO3- ions could be readily hydrated with water molecules, causing the plasticization effect on the chains of cellulose acetate. The coordinative interactions between the CA and Cd(NO3)(2)4H(2)O were investigated by IR spectroscopy. The change of ionic species in Cd(NO3)(2)4H(2)O was analyzed by Raman spectroscopy.