Unexpected in-situ Free Radical Generation and Catalysis to Ag/Polymer Nanocomposite

In this study, we discover unexpectedly that simple reaction of AgNO3 with oleic acid (OA) without solvent and surfactant could generate alkyl free radical which can catalyze double-bond polymerization of OA to form 1D polymeric oleic acid (POA) chain. In certain conditions, these POA chains circumvolute tightly each other to form microspheres and micro-plates in which monodisperse 4-5 nm Ag nanoparticles (NPs) were absorbed. It has been revealed that alkyl free radical generated during the redox reaction of carboxyl group of OA with Ag(+) at relative low temperature. Then, the alkyl free radical catalyzed the double-bond polymerization of OA when the reaction temperature was further increased. Different from commonly-seen hydrophobic nanoparticles prepared in oleic acid-based microemulsion system, the nanocomposites cannot dispersed in n-hexane and could dispersed in ethanol and THF. The unusual dispersion behavior has been explained in terms of their structure and polarity of POA chain. The method combines the nucleation of Ag nanoparticles and the polymerization of monomer in a facile one-pot reaction, which provides a novel way for metal-polymer microsphere nanocomposite with low-cost, easy-operation and high-yield.