Influence of a long-chain alkane on the photoinduced nematic-isotropic transition.
We investigated the phenomenon of photoinduced nematic-isotropic (N-I) transition for different concentrations of a long-chain alkane, viz., octadecane (OD), and a host liquid crystalline material having a small quantity (4.5 mol %) of a photoactive azo compound. As expected, the N-I transition temperature diminishes with increasing concentration of OD. Data of time-resolved measurements of the dielectric constant through both the UV-activated trans-cis transformation and the thermal back relaxation process are presented. With increasing concentration of OD, although the response time for the former process increases slightly by less than a factor of 2, the thermal back relaxation shows a greater increase by more than an order of magnitude. As a possible explanation for this surprising result, we discuss an argument based on the structural incompatibility of the constituents of the system investigated.
Centre for Liquid Crystal Research, Jalahalli, Bangalore 560 013, India.
Geetha G
GG
Nair
S Krishna
SK
Prasad
Gurumurthy
G
Hegde