Identification of phase transition temperatures by statistical image analysis

Abstract

Analysis of the textures and phase transitions of thermotropic liquid crystals p-ethoxybenzylidene-p-n-butylaniline, cholesteryl myristate and cholesteryl decanoate was carried out using a polarising optical microscope under crossed polarisers attached with a hot stage and a high-resolution camera. Using MATLAB software, the statistical parameters, such as mean, standard deviation, root mean square, contrast and entropy of the textures as a function of temperature, are computed. These results show abrupt changes as a function of temperature, indicating the phase transition of the sample. The statistical image analysis of various liquid crystal samples are in good agreement with the literature results and the proposed methodology offers a reliable and very sensitive technique to identify mesophase transition temperatures.

Keywords:

• phase transition temperatures
• thermotropic liquid crystals
• statistical image analysis
• statistical parameters

Acknowledgements

The authors gratefully acknowledge Project No. ERIP/ER/0703688/ M/01/ 1134, dated 31 March 2010, of DRDO, the UGC DRS LEVEL III program No.F.530/1/DRS/2009 (SAP-I), New Delhi, dated 9 February 2009, and the Department of Physics, Acharya Nagarjuna University, for providing financial assistance.