Comparison between densitometer and dilatometer measurements in liquid-crystal phases

摘要

This study focuses on a comparison between densitometer and dilatometer measurements of two liquid-crystal systems: the 4-methoxybenzylidene-4'-butlylamiline (MBBA) system and a micellar system consisting of octyammonium chloride (OACl) and water. The measurements are taken near two phase transitions: the nematic-isotropic and the hexagonal-isotropic. The former refers to the MBBA and the latter to the OACl. It is observed that whereas, at the nematic-isotropic phase transition, the densitometer and dilatometer measurements exhibit a similar step density change, at the hexagonal-isotropic transition the densitometer measurements show a step density change which is about five times larger than the one detected in the dilatometer experiments. The results are discussed and compared to other liquid-crystal systems.