Rheological Properties of Poly(acrylonitrile-co-methyl acrylate)/Clay Nanocomposites Prepared via Emulsion Polymerization

Poly(acrylonitrile-co-methyl acrylate)/clay nanocomposites were prepared by free radical polymerization in emulsion using 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS) as a compatibilizer. The resultant nanocomposites were of partially exfoliated morphology despite the variations in clay content among the nanocomposites, as confirmed by transmission electron microscopy and small-angle X-ray scattering analysis. Rheological studies of these materials were carried out using parallel plate geometry. The storage modulus increased monotonically with increasing clay content throughout the frequency range studied. However, the neat copolymer, poly(acrylonitrile-co-methyl acrylate) and its nanocomposites, exhibited long relaxation behavior as the storage modulus (G') was greater than the loss modulus (G '') throughout the angular frequency range studied. The complex viscosity of the nanocomposites increased with increasing clay content and they exhibited shear-thinning behavior. Despite the enhanced rheological properties observed, the copolymer and its nanocomposites underwent structural changes during oscillatory measurements due to cyclization reactions. POLYM. COMPOS., 32:59-66, 2011. (C) 2010 Society of Plastics Engineers