Analysis of surface anchored lattice plane orientation in blue phase liquid crystal and its in-plane electric field-dependent capacitance response

Uniformly oriented macroscopic monodomain of cholesteric blue phase liquid crystal has been realised by the influence of surface anchoring. Orientation of the lattice planes in surface-treated (ST) and non-surface-treated (NST) cell were analysed and compared by Kossel diagram technique. NST cell has revealed the green and blue domains corresponding to reflection from oriented (110) and (112) planes of the body-centred cubic lattice. However, in the ST cell only the lattice plane (110) oriented uniformly and tailored the macroscopic monodomain. Electric field driven reorientation of the (110) lattice plane was noticed in NST cell whereas for ST cell such reorientation was absent. Two distinct electric field-induced capacitive responses have been observed in the two different cells. In NST cell anomalous electrostriction was observed, whereas for ST cell normal electrostriction was observed. Interestingly, the capacitance has decreased with an increasing electric field for anomalous electrostriction in NST cell, whereas for normal electrostriction in ST cell it was increased with increasing the field. Such a capacitive change behaviour is explained by dielectric anisotropic change followed by the electric field induced elongation and contraction of the cubic unit cell along and perpendicular to the electric field.