Smectic polyester/layered silicate nanostructured hybrids: Effect of modified nanoclay in the phase transitions

The effect of incorporating different proportions of a layered silicate nanofiller into poly(diethylene glycol p,p’-bibenzoate) has been analysed. On cooling from the isotropic melt, this thermotropic main-chain liquid-crystalline polymer exhibits a smectic mesophase which is able to crystallise rather slowly by long time annealing. The results show that the nanocomposites exhibit a higher stability against thermal decomposition in oxidative atmosphere. The intercalation of polymeric chains into the clay layers is deduced from X-ray diffraction, although part of the initial silicate structure is preserved. The DSC results indicate a clear nucleation ability of the clay for both mesophase formation and crystallisation from the mesophase. The effect in this crystallisation is of major importance, causing a reduction of the time necessary to attain 50% of the total transformation by a factor of more than 4. Additional information was obtained from microhardness measurements.