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Phase Equilibria and Critical Behavior in Nematogenic MBBA-Isooctane Monotectic-Type Mixtures
Jakub Kalabiński1, Aleksandra Drozd-Rzoska1, Sylwester J Rzoska1
1Institute of High Pressure Physics Polish Academy of Science, ul. Sokołowska 29/37, 01-142 Warsaw, Poland.
International Journal of Molecular Sciences
|February 11, 2023
Summary
This study investigates liquid crystal phase transitions in MBBA and isooctane mixtures, revealing two distinct biphasic regions. Anomalous behavior and critical opalescence were observed, with pretransitional fluctuations differing between the two regions.
Area of Science:
- Materials Science
- Physical Chemistry
- Soft Matter Physics
Background:
- The isotropic (I) to nematic (N) liquid crystal phase transition is a universal phenomenon in suspensions of elongated particles.
- Rod-like liquid crystalline (LC) compounds and their mixtures offer insights into universal features of these transitions.
Purpose of the Study:
- To investigate the phase behavior of 4'-methoxybenzylidene-4-n-butylaniline (MBBA) and isooctane (Sol) mixtures.
- To characterize the biphasic regions and pretransitional phenomena in this system.
Main Methods:
- Phase diagram determination, identifying monotectic-type behavior.
- Analysis of biphasic coexistence curves using order parameter and diameter tests.
- Nonlinear dielectric effect (NDE) measurements to study pretransitional fluctuations.
Main Results:
- A monotectic-type phase diagram with two biphasic regions (TP1: I-N coexistence; TP2: liquid-liquid coexistence) was found.
- Anomalous mean-field behavior near the critical consolute temperature and critical opalescence were observed.
- Pretransitional fluctuations in the isotropic liquid phase exhibited classic (mean-field) behavior above TP1 and non-classic behavior above TP2.
Conclusions:
- The MBBA-isooctane system serves as a model for understanding universal aspects of liquid crystal phase transitions.
- Distinct pretransitional fluctuation behaviors were identified in the isotropic phase above the two biphasic regions.
- The study resolved issues concerning non-critical background effects in NDE measurements.
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