Polymer/silicate nanocomposites synthesized with potassium persulfate at room temperature: polymerization mechanism, characterization, and mechanical properties of the nanocomposites

Abstract

Polymer/silicate nanocomposites were synthesized using potassium persulfate (KPS) in the presence of silicate and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) without exterior redox co-catalysts at a room temperature. A mechanism for the room temperature polymerization in the presence of silicate was suggested: AMPS attached on the surface of silicate layers would oxidize Fe+2 in silicate lattice to become Fe+3 and the Fe+3 would decompose KPS to form radicals like redox co-catalysts. Poly (acrylonitrile) (PAN)/silicate nanocomposite showed an exfoliated structure, but poly (methyl methacrylate) (PMMA)/silicate nanocomposite showed an intercalated structure. Polymers recovered from the nanocomposites synthesized at a room temperature had high isotactic configurations compared to bulk polymers. The dipole-dipole interaction between monomers and silicate surface might make the lamella of monomers to form on the silicate layer surface and produced polymers with more isotactic configurations. PAN/silicate nanocomposite showed two glass transition temperatures at 113 and 151 degreesC. The lower temperature might be related to the molecules with low molecular weight. PMMA/silicate nanocomposite had a storage modulus of 4.47 x 10(9) Pa at 40 degreesC. (C) 2003 Elsevier Ltd. All rights reserved.