Measurements of the ratio of the Frank constants for splay and bend in nematics of disc-like molecules

Publisher Website
Google Scholar
Abstract
We report measurements of the magnetic Frederiks transition in nematics consisting of disc-like molecules (2, 3, 7, 8,12,13-hexa(alkanoyloxy)truxenes). We find that in these materials the splay elastic constant K1 is larger than the bend elastic constant K3 throughout the nematic regime, in contrast to what is commonly observed in fluids of rodlike mesogens. This behaviour is in agreement with the behaviour predicted by mean-field theory [1]. At the transition from the nematic to the high-temperature columnar phase the ratio K1/K3 appears to approach unity. We find no evidence for the predicted pretransitional enhancement of the ratio K1/K3 due to columnar order parameter fluctuations [2]