The orientation-enhancing effect of diphenyl aluminium phosphate nanorods in a liquid-crystalline epoxy matrix ordered by magnetic field

• Magnetic-field-oriented liquid crystalline nanocomposites were synthesized.
• Diphenyl aluminium phosphate nanorods were used as filler.
• The cuboid but anisotropic filler nanocrystallites distinctly align in the field.
• The nanofiller strongly enhances the orientation of the LC matrix.
• Interactions with the filler nanocrystallite surface seem to align the matrix.

Nano-crystallites of diphenyl aluminium phosphate (NR), the polymeric molecules of which display a nanorod-like shape, were incorporated as an orientation-enhancing agent into an epoxy matrix, which was obtained by the cure of a liquid crystalline diepoxide containing a triaromatic mesogenic group. The crosslinking component of the matrix was 4,4′-diaminodiphenylmethane. Samples of the neat matrix and of the composite with NR were oriented by applying an external magnetic field during their cure. The cure process was investigated by DSC and in-situ rheology, and the obtained products were characterised by TEM, 1D- and 2D-SAXS/WAXS, DSC and DMTA. It was demonstrated, that the cuboid but anisotropic NR crystallites become oriented and highly enhance the ordering of the liquid crystalline matrix in the magnetic field. Some spontaneous ordering by NR was observed even without any field. The ordering effect of the field was stronger if it was perpendicular to, rather than parallel with the main surface of the flat samples. The dynamic-mechanical properties of the products displayed the expected anisotropy, while their thermal transitions were found to be sensitive to the achieved degree of ordering.

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