Kinetics of the isotropic–nematic phase transition in melted multi-component liquid crystal mixtures upon cooling

Abstract

The kinetics of the phase separation and the nematic phase growth in two melted commercial multi-component liquid crystal mixtures upon cooling was studied using polarising optical microscopy and IR spectrometry. The droplets of the nematic phase revealed in the optical images across the phase transition were segmented and treated statistically. In the resulting size histograms of mixture B, two overlapping statistical ensembles related to two co-existing nematic phases were recognised; these phases were shown to be different in their chemical structures. In mixture A, any separation within the nematic phase was not found. The statistical ensembles of the nematic droplets were successfully described using the principles of irreversible thermodynamics. Analysis of the mean droplet diameter as a function of time allowed recognition of two regimes of the nematic phase evolution: (1) nucleation and rapid nucleus growth and (2) nucleus coalescence. Both the regimes were quantitatively described with the universal law for the cluster growth.