Photoinduced phase transitions in liquid crystalline systems

In recent years, a field of research that is growing steadily is the photoinduced phenomenon in which the incident light itself brings about molecular ordering/disordering of the liquid crystalline system. This particular aspect of photonics, in which light can be controlled by light as a stimulus, is being proposed as the future technology for high-speed information processing and photochromic materials. The azo compounds in particular, have been found to be promising candidates for optical data storage. An illustration of nature utilizing photoinduced effects is that of the biological photochrome bacteriorhodopsin found in the eye. Apart from their biological and technological importance, these systems exhibit photo-driven phase transitions, thus providing a new tool to study phase transitions and the associated critical phenomena. In this article we review some of our recent contributions to this field of photoinduced isothermal phase transitions in various liquid crystalline systems. In particular, we discuss the application of the random-field Ising model to describe the photoinduced nematic-isotropic transition, the influence of nanophase segregation to bring about a unique photo-driven disorder to order transition, local racemization phenomenon in bentcore banana B-2 phase and the effect of high pressure.