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Abstract
The influence of the sorbed N2 on the surface tension of the low molecular liquid crystal MBBA (p-methoxybenzylidene-p ′-n-butylanilin) has been investigated using the pendant drop method. The time- and temperature-dependent measurements of the surface tension of MBBA have been carried out under different N2 pressures (1–15 bar). The time-dependence of the surface tension is interpreted in terms of the sorption process of N2. The results depend strongly on the liquid crystal (LC) phase, the gas pressure and the gas type. All the temperature-dependence curves of the surface tension of MBBA, obtained at different N2 pressures, show a similar shape within the experimental temperature range (25–50°C), yet with a systematic decrease of the phase transition temperature isotropic (i)/nematic(n) by the increasing N2 pressure and thus the increasing concentration of the sorbed gas in the sample. The positive slope of the surface tensiontemperature characteristic near the phase transition temperature indicates the development of higher ordered molecular states in the surface layer. The correlation between the i-n phase transition temperature of LCs and the concentration of sorbed gases, the gas type and the impurities in LCs has been also discussed.