Chitosan/Silver Nanoparticles Composite: Molecular Relaxations Investigation by Dynamic Mechanical Analysis and Impedance Spectroscopy

By impedance spectroscopy, Gonzalez-Campos et al. J Polym Sci Part B: Polym Phys 2009, 47, 932-943, reported the first evidence of a glass transition in a polysaccharide. To gain a better understanding on the molecular relaxations in polysaccharides, we study composites of chitosan (CS)/silver nanoparticles (AgnP) films by dynamic mechanical analysis (DMA) and dielectric spectroscopy in the 2-250 degrees C temperature range. CS/AgnP films conductivity increases in two orders of magnitude in comparison with pristine CS. Three relaxation processes ascribed to the alpha-relaxation, sigma-relaxation, and degradation process have been observed for the first time. Molecular dynamics and conductivity strongly depends on moisture content; since a plasticizing effect on the glass transition temperature is observed, similarly the increase in AgnP weight percent leads to a glass transition temperature decrease and also increases CS thermal stability. Infrared spectroscopy analysis reveals the AgnPs interaction with OH, NH2, CO.NH2, and C-O-C groups implying an evident redistribution of the vibration bands for these groups. These new bonds affects the molecular dynamics of the CS chain bearing important changes in relaxations processes when compared CS/AgnP composite with pristine CS. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part 6: Polym Phys 48: 739-748, 2010