Electron paramagnetic resonance studies of a viscous nematic liquid crystal. II. Evidence counter to a second-order phase change

The ordering in a viscous nematic liquid crystal was studied using vanadylacetylacetonate and several nitroxides as paramagnetic probes. The ordering curve for VAAC at both K-band and X-band shows a slope discontinuity at a reduced temperature of 0.85. This discontinuity is caused by the tumbling time of the VAAC becoming comparable with the hyperfine splitting. The slope discontinuity is not present in the ordering curves of the nitroxides. The results are taken as evidence counter to the presence of a second-order phase transition.