Inverse gas chromatographic characterization of polystyrene and organo-montmorillonite/polystyrene nanocomposites

Polymer nanocomposites of a polystyrene (PS) matrix containing 2% and 5% organo-montmorillonite (OMt) by mass were prepared using the solution blending method with sonication. Hexadecyl trimethyl ammonium bromide was used to modify the montmorillonite after its surface was saturated with Na+ ions. X-ray diffraction and transmission electron microscopy revealed the mixed nanomorphology of nanocomposites. The majority of OMt is dispersed in the polymer matrix in the form of an ordered tactoid (multilayer particles) structure consisting of few silicate layers and a small amount of exfoliation was achieved. The synthesized nanocomposites showed a higher decomposition temperature in comparison with pure PS according to the thermogravimetric analysis. Inverse gas chromatography under infinite dilution conditions was applied to evaluate the surface properties of the PS and OMt/PS nanocomposites. The IGC results were in agreement with conceptual and theoretical expectations. The dispersive component of the free energy of adsorption and specific interactions (acid-base properties) were determined using polar and non-polar adsorbates (probes) of known properties in the temperature range 40-70 degrees C. The IGC data showed that the introduction of a very small amount of OMt into the polymer matrix significantly changed the surface characteristics of the final material.