Nematic phase formation of Boehmite in polyamide-6 nanocomposites

Nematic phase behavior of titanate-treated Boehmite rods in a polyamide-6 matrix is reported. Optical polarization microscopy (OPM) and wide-angle X-ray scattering (WAXS) performed during heating and cooling cycles, are used to provide information on the level of orientation of Boehmite rods and polyamide-6 crystallites. The nematic orientation of Boehmite is clearly indicated by the permanent birefringence in OPM, which persists above the melting point of the polymer. The WAXS data show that the projection of Boehmite peaks on the 2D detector transform from isotropic to anisotropic as the Ti-Boehmite concentration is increased, regardless of temperature or the physical state of the polymer. Nematic order parameters are obtained by fitting a Maier–Saupe type function into the WAXS intensity curves. According to that, nematic order of the Boehmite peak increases gradually with the Ti-Boehmite content and it is unaffected by the heating–cooling cycles. As for the polyamide-6, nematic order of the γ-phase and one of the α-phase peaks decrease while that of the other α-phase peak increases with the number of cycles. Based on these observations, a structure for the colloidal liquid crystalline nanocomposite samples is proposed.