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The influence of pretransitional phenomena on blue phase range

 

作者: R.J. Miller,   H.F. Gleeson,  

 

期刊: Liquid Crystals  (Taylor Available online 1993)
卷期: Volume 14, issue 6  

页码: 2001-2011

 

ISSN:0267-8292

 

年代: 1993

 

DOI:10.1080/02678299308027736

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

The particular phase in which a liquid crystal system will exist is that which has the lowest free energy at a certain temperature. The free energy may depend on variables such as temperature, pressure, chirality, etc. One way in which the stability of a particular thermodynamic phase, relative to its neighbours, would be manifest is in its temperature range. The effect of chirality, in particular, on the temperature range or stability of blue phases has been well-studied both experimentally and theoretically. To date these studies assume that chirality is the only parameter which will influence the existence of blue phases. However, blue phases with relatively low chirality and broad range, which should in principle only show very narrow blue phases, have been reported. This suggests that factors other than chirality are involved in blue phase stability. In this paper we investigate the phase stability of various blue phase mixtures containing equal amounts of a chiral dopant, via their blue phase temperature range. Correlation between blue phase stability and the elastic constantsk2andk22, molecular length of the nematic host, and the order parameter at the blue phase to cholesteric transition is discussed. We have confirmed that for our mixtures the total blue phase temperature range may be related equally to the elastic constantk22and the chirality. We also present the first data displaying an odd-even effect in blue phases. Finally, we have found an apparent correlation between the stability of the blue phases and the magnitude of the orientational order parameter of the cholesteric phase at the cholesteric to blue phase transition.

 

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