Photo- and thermal-processing of azobenzene-containing star-shaped liquid crystals

Abstract

A new class of star-shaped, liquid crystalline, low-molecular weight compounds functionalized with photochromic azobenzene and mesogenic groups was investigated in terms of light-induced anisotropy. The behaviour of the materials under the action of light with simultaneous or subsequent thermal treatment was examined with respect to the induction of anisotropy. The unconventional UV light treatment prior to the irradiation with linearly polarized light allowed induction of very high values of anisotropy (D = 0.77) at room temperature. Moreover, the simultaneous action of light and temperature led to the induction of higher values of dichroism in comparison with anisotropy generated by the standard procedure. Subsequent thermal treatment led to dewetting and the formation of 3D macroscopic stripe- and dome-like structures for one of the investigated compounds. Despite photoinduction of anisotropy by a single beam, the formation of polarization and surface relief gratings by two-beam interference pattern was also investigated.