Properties of Polystyrene Clay Nanocomposites Prepared Using Two New Imidazolium Surfactants

Montmorillonite/polystyrene nanocomposites were prepared by in situ photopolymerization of styrene in the presence of 2% by weight of clay organomodified by two new imidazolium surfactants having in their structure an alkyl chain with 20 or 22 carbon atoms, respectively. Thermogravimetry showed that the new surfactants are more thermally stable than conventional alkylammonium surfactants. The properties of the obtained nanocomposites were compared with those of pristine polystyrene, with those of a microcomposite obtained by in situ polymerization of styrene in the presence of unmodified clay, and with those of a nanocomposite obtained starting from an organomodified clay with a short alkyl chain (12 carbon atoms) imidazolium surfactant. XRD, TEM, and rheological analysis showed that the clay/PS nanocomposites have a mixture of intercalated and partially exfoliated structure layers, where the higher the surfactant alkyl chain length, the higher the exfoliation degree. Kinetics curve of accelerated UV aging, obtained by following through infrared spectroscopy the increase of carbonyl functions during aging, showed that the rate of photooxidation of clay containing samples is higher than neat polystyrene. The rate is higher as a function of the degree of dispersion of the filler in the polymer matrix.