Effect of organoclay on the orientation and thermal properties of liquid-crystalline polymers

The preparation and thermal and thermo-mechanical properties of nanocomposites based on liquid-crystalline polymers (LCP) and organically-modified layered silicate (OMLS) is described. From XRD patterns, very little smectic ordering is present in the pure LCP; in the nanocom posites, the polymer chains tended to orient in the direction of the dispersed clay layers. According to the DSC results, during first heating, the first melting peak represents the crystalline to nematic transition and, after that, a broader isotropization takes place. Although TGA of the samples showed a single-step decomposition through chain scission under an inert atmosphere, in air the nanocomposites underwent a two-step process, with onset of degradation at a higher temperature. The first step is mainly due to chain scission and the second is due to oxidative reactions.