Break columnar phases

We start with some elementary information about anisotropic intermolec-ular interactions in liquid crystals and molecular factors that influence the smectic behaviour. The various types of molecular models and commonly accepted concepts reproducing the smectic behaviour are evaluated. Then we discuss in more detail the breaking of head-to-tail inversion symmetry in smectic layers formed by polar and (or) sterically asymmetric molecules and formation of particular phases with one and two dimensional periodicity. We then proceed with the description of the structure and phase behaviour of terminally fluorinated and polyphilic mesogens and specific polar properties of the achiral chevron structures. Finally, different possibilities for bridging the gap between smectic and columnar phases are considered. 

Oscillating forces are not a prerogative of smectics, but have been reported as well for nematics [45,50,51] and even for simple liquids of nearly spherical molecules [52]. In fact, as it was mentioned in the Introduction, the presence of a molecularly flat surface always produces some layering (i.e. positional ordering) of the nearby liquid molecules, because it breaks the translational invariance of the liquid. In liquid crystals this tendency is often enhanced by the presence of a fully layered bulk phase at low temperature (smectic, hexatic, columnar phases, etc.). 

First, simple less homogeneous - and therefore likely to be more prevalent among chemically disperse membranes - lower symmetry variations on the known mesostructures deserve consideration. Consistent reports of other mesophases by experienced researchers of the calibre of Luzzati and Fontell in Sweden cannot be discounted (17). Most of the proposed mesostructures involve simple symmetry-breaking deformations of the more common phases, including hexagonal columnar and discrete micellar mesophases. 

Keith C, Reddy RA, Tschitaske C (2005) The first example of a liquid crystalline side-chain polymer with bent-cme mesogenic units ferroelectric switching and spontaneous achiral symmetry breaking in an achiral polymer. Chem Commun 7 871-873 Keith C, Dantlgraber G, Amaranatha Reddy R, Baumeister U, Tschierske C (2007) Ferroelectric and antiferroelectric smectic and columnar liquid crystalline phases framed by silylated and non-silylated molecules with ilurainated bent Cotes. Chtan Mater 19 694-710... 

The above discussion concentrated mainly on the behavior of nanospheres. Understanding the thermodynamics of nanoplatelets and nanorods in polymers is even more complicated, since their anisotropy often leads to the breaking of orientational symmetry and formation of various ordered phases (nematic, smectic, columnar, etc.). We refer the readers to recent reviews [13, 78] for more information of these topics. 

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