Enhanced thermal and mechanical properties of chitosan membrane by silver nanoparticles Chih-Wei Chou1, Yung-Hsiu Chen1, Ko-Shao Chen2 1Department of Cosmeceutic, China Medical University, Taiwan, 2Department of Materials Engineering, Tatung University, Taiwan In this study, we have prepared the nanocomposites of chitosan incorporated with two type silver (Ag) nanoparticles (Ag 1, 25 nm and Ag 2, 45 nm). The nanoparticle size, dispersion, thermal stability, mechanical properties, surface morphology, and free radical scavenging ability of nanocomposites were characterized in vitro. The Ag 1 and Ag 2 exhibited a homogeneous dispersion in chitosan matrix. A significant increase in the thermostability and mechanical properties of the polymer was demonstrated in the nanocomposite chitosan films, which was believed a result of induced crystallization in the presence of Ag nanoparticles. The better free radical scavenging effect was associated with the surface morphological change in the presence of Ag. The nanocomposite containing 30 ppm of Ag 1 or 60 ppm of Ag 2 was found to possess optimal free radical scavenging ability, and much increased biocompatibility in vitro.