Orientational fluctuations and phase transitions in 8CB confined by cylindrical pores of the PET film

Abstract

Results of optical investigations of the isotropic-nematic and nematic-smectic A phase transitions in porous polyethyleneterephthalate (PET) films filled with octyl-cyanobihenyl (8CB) liquid crystal (LC) are reported. Samples of porous films of thickness 23 µm with normally oriented cylindrical pores of a radius R ranging from 10 nm to 1000 nm were prepared using the track-etched membrane technology. The dynamic light scattering method was used to probe the nematic orientational fluctuations of confined LC samples. The corresponding relaxation time τ was measured as a function of R and temperature T at slow enough cooling rates (0.3–0.6 K/h) to locate the phase transition temperatures. Changes in τ(T) dependencies relatively sensitivity fingerprint the LC phase transformations. Experimental results are analysed using the Landau-de Gennes-Ginzburg phenomenological approach.     

Investigation of aerosol formation during benzaldehyde photolysis

The kinetics of photolysis and photonucleation of benzaldehyde (BA) vapor in the air and in an inert gas is investigated, along with the physical and chemical characteristics of the resulting aerosol particles. Short-lived free radicals that accompany the BA photonucleation process were identified by means of spin trapping. Numerical simulation of BA photonucleation, combined with the proposed chemical mechanism, allowed us to calculate the rate of generation of initial particles and to estimate the aerosol quantum yield.