Study of polymer liquid crystals by gas chromatography

The technique of inverse gas chromatography (i.g.c.) has been used to investigate the transitions between liquid-crystalline phase in a polysiloxane bearing cyanobiphenyl mesogens and in a low-molar-mass analogue. The transition temperatures were found by considering the variation of retention volume with temperature and also the activity coefficients of the probes used, the latter giving clearer results. The possibility of using the method to study the thermodynamics of the transitions is also discussed. Although not the most convenient method for measuring solely the phase transitions, it allows the simultaneous determination of a number of other properties, so that our results extend the already wide range of applicability of i.g.c. in polymer science.