Poly(aspartic acid) and its thin film were synthesized to study proton transport properties. The average degree of polymerization and molecular weight are 50 and 7000, respectively. The proton conductivities of the Poly(aspartic acid) and its thin film were 4.3 x 10(-4) and 5.1 x 10(-3) S cm(-1), respectively under the relative humidity of 70% and 298 K. The proton conductivity of the thin film is one order of magnitude higher than that of the pelletized Poly(aspartic acid). The activation energies for the proton conduction of the pelletized Poly(aspartic acid) and thin film are 0.65 and 0.53 eV. respectively. The open circuit voltage of the pelletized sample exhibited -0.9 V under the relative humidity of 70% and 298 K. (C) 2009 Elsevier B.V. All rights reserved.