Nanocomposite of polymer liquid crystal/single wall carbon nanotubes: isothermal and non-isothermal phase kinetics

In the last decades, great body of interest is given to the design of polymer nanocomposites with carbon nanotubes, since such materials possess great potential for various applications. The present report deals with kinetics of phase formation of nanocomposite consisting of thermotropic polymer liquid crystalline poly(heptane-1,7-dyil-biphenyl-4,4'- dicarboxilate), P7MB, and 1 wt. % single wall carbon nanotubes. Excellent dispersion of nanotubes, proven by scanning electron microcopy, was achieved. It was due to separate ultrasonication of both constituents in solvent and consequent mixing. This approach resulted in excellent non-covalent bonding and formation of nanofibers with a diameter of about 150 nm. Investigation on kinetics of structural formation at different iso- and non-isothermal conditions was performed by means of differential scanning calorimetry. The results showed that cooling down the isotropic melt state, a smectic phase transition takes place in a very short time for both – neat P7MB and the nanocomposite. At lower temperatures, there is a partial crystallization. The smetic phase formation happens in identical way in all cases. However, there is a considerable difference in the way of crystalline phase formation, originating from the special restrictions, introduced by the nanotubes. Non-isothermal phase kinetics was followed by modified Avrami, Ozawa, Liu and Mo approaches.