Influence of Gas Sorption on Surface Tension of Liquid Crystalline Substances:—Influence of CO2 on Time-dependence of Surface Tension

Abstract

As one part of the experimental studies on the influence of gas sorption on the surface tension of liquid crystalline substances (LCs), this paper reports on the CO2 sorption in low molecular LC MBBA (4-methoxybenzylidene-4′-n-butylaniline) and thus caused the time-dependence of surface tension. The experiments have been performed in the CO2 atmosphere over the temperature range which covered the phase transitions of MBBA, and at pressures up to 15 bar. Separately, the surface tension measurements and the gas sorption measurements have been carried out under the same experimental conditions, by using a computer-aided measuring setup based on the pendant drop method and a high pressure electromicrobalance, respectively. The paper provides experimental evidences for our previous suggestion, that the unusual time-dependence of surface tension of the freshly formed LC surfaces may be mainly attributed to the gas sorption processes, by comparing the results from above different measurements. The paper also reports the phase transition behaviors of MBBA as a function of the sorbed gas concentration, and the reversibility of the CO2 sorption.