Abstract
ABSTRACTThe rational design of calamitic liquid crystals is an area of research that has been intensively explored due to their extensive applications in various devices. The successful methods for design have been, to some extent, mapped on discotic systems such that certain features of the structures of calamitic phases have been superimposed upon those of nematic discotic and columnar phases. In this article, we explore the correlation between nematogenic behaviour of hard rod-like particles and that of hard disc-like systems. We show that for calamitics, nematic behaviour is observed, whereas for discotics this is not the case. Furthermore, we show that nematic discotic materials are miscible, whereas unlike smectics, columnar phases are less likely to be miscible. Indeed, it appears that columnar discotic phases are greater similarities with soft-solids than true liquid crystals.
Highlights
Theoretical modelling of liquid crystals usually starts with assuming that the molecules are effectively particles with anisotropic shapes, with rod-like topologies being the most preferred
If we consider Onsager’s model and draw a direct comparison between calamitic and discotic systems, we find that for calamitics the aspect ratio for the rod-like bodies is important in the formation of nematic phases [25]
The first set of observations suggests that there could be an additional interaction occurring at the 10 mol% point, both in the solid state and in the mesophase, whereas for the second set there appears to be competition between the components that suppresses clearing point, but which supports the solid state. These results demonstrate that the interactions in the solid state are not necessarily so important to the liquid crystal phases, which confirms what is known about paramorphosis – that the solid state does not necessarily influence phase transitions and behaviour in the liquid crystal state, and that there must be donor–acceptor core–core interactions arising from different local charge distributions that is maximised for certain concentrations, as discussed later
Summary
Theoretical modelling of liquid crystals usually starts with assuming that the molecules are effectively particles with anisotropic shapes, with rod-like topologies being the most preferred. They mixed amphiphilic discotic liquid crystal materials with triphenylene and pyrene to determine the virtual phase transitions temperatures.
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