The Structure and Electric Characters of Proton-Conducting Chitosan Membranes with Various Ammonium Salts as Complexant

The structural and electric properties of chitosan electrolytes doped by three different ammonium salts [CH3COONH4, NH4Cl, and (NH4)(2)SO4] were discussed. The chitosan electrolytes were prepared by solution casting technique. The results show that the addition of ammonium salts leads to: The formation of complexation between ammonium salts and chitosan matrix, the destruction of crystal forms, and the enhancement of amorphous nature. With the rise of salt content, both the glass transition temperature and the activation energy show a V-type trend, whereas the conductivity exhibits a reverse trend. For different ammonium salts, the electric properties of the chitosan electrolyte are different due to the Coulomb force between anion of salts and functional groups. The CH3COONH4 doped chitosan electrolyte exhibits the optimum electric properties, whereas those of (NH4)(2)SO4 doped chitosan electrolyte are worst. The chitosan electrolyte doped with 40 wt % CH3COONH4 has the lowest glass transition temperature of 369 K, the lowest activation energy of 0.19 eV, and the highest ionic conductivity of 2.87 x 10(-4) S cm(-1) at room temperature. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 880-885, 2010