Effect of the intercalated/exfoliated nanostructure on the phase transformations of smectic polyester/layered silicate hybrids: Reinforcement of the liquid-crystalline matrix

Smectic poly(triethylene glycol p,p'-bibenzoate) (PTEB)/clay hybrids were prepared by a solution blending method. Unmodified (cloisite (R) Na) and two organically modified (cloisite (R) 10A and cloisite (R) 15A) montmorillonites were used. The morphology of the hybrids was characterized by TEM and X-ray diffraction. It has been found that a conventional microcomposite is obtained from unmodified montmorillonite, while intercalated/exfoliated nanocomposites are produced from organoclays. Dynamic DSC and X-ray synchrotron studies show that the liquid-crystalline character of PTEB is preserved in the hybrids, and both the cooling phase sequence (isotropic melt-SmA-SmC) and smectic layer thickness of PTEB are practically unaffected by the presence of clay particles. However, the kinetics of evolution of PTEB to their different ordered states (liquid-crystalline and crystal) certainly depends on the morphology. Moreover, the effect of the clay morphology in the tensile reinforcement of the liquid-crystalline matrix is also analysed. The intercalated/exfoliated nanostructures show an increase about 200% in Young's modulus. (C) 2009 Elsevier Ltd. All rights reserved.