Structure and morphology of nanocomposite films prepared from polyvinyl alcohol and silver nitrate:: Influence of thermal treatment

Hybrid organic/inorganic films have been prepared from an aqueous solution of polyvinyl alcohol (PVA) and silver nitrate (AgNO3). The silver nanoparticles have been generated in the PVA matrix by thermal treatments. The structure and the morphology of the hybrid films have been studied as a function of the silver precursor concentration and of the annealing conditions for a wide range of annealing temperatures. It was shown that in the uncured hybrid film most of the silver ions were initially coordinated with the polymer OH groups to form a chelate structure. A nanostructuration effect leading to the formation of crystalline silver nanoparticles was evidenced for annealing treatments performed at temperatures higher than 90 degrees C. For a curing temperature equal to 110 degrees C, the sizes of the formed nanoparticles were only slightly increasing as a function of annealing time and the effect of AgNO3 complex amount in this curing condition was also significant, but slight. Annealing at a temperature equal to 160 degrees C thus at a temperature for which a part of the crystalline phase of PVA was melt led to an important increase of the size of the generated metal nanoparticles. The evolution of the morphology was discussed for each curing temperature as a function of the kinetics of the nanostructuration, of the size of the matrix amorphous lamellae and of the polymer chain mobility. (c) 2007 Wiley Periodicals, Inc.