Abstract
As a part of the systematic studies on symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4′-oxy) alkanes, (referred to as m.OnO.m with m = 3, 4, and 5; and n = 8, 9, and 10), we present in this article the nature of phase transitions across isotropic–nematic and nematic–smectic-A (N–SmA) phases exhibited by the just mentioned compounds. The methods employed are differential scanning calorimetry and dilatometry. The compounds studied were 3.O8O.3, 4.O8O.4, and 5.O8O.5; and 3.O9.03, 5.O9O.5, 3.O10O.3, 4.O10O.4, and 5.O10O.5. Different from the case of their corresponding monomers, all these compounds exhibit a nematic phase only with the exception of 5.O8O.5 which exhibits a SA phase in addition to the nematic phase. The phase transitions viz., isotropic–nematic transitions studied in all these compounds were confirmed to be of first-order nature, whereas the N–SmA transition exhibited by the compound 5.O8O.5 only was found to be of second-order nature. We also report in this article the calculated density jumps, thermal expansion coefficient maxima, and pressure dependence of transition temperatures which are analyzed in the light of the available literature data.
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Acknowledgements
P. Pardhasaradhi and P. V. Datta Prasad thank the Management and the Principal of The Hindu College, Machilipatnam for providing facilities to carry out the measurements. D.Madhavi Latha and Dr. V.G.K.M. Pisipati express their thanks to the management of K.L.University, Vaddeswaram 522 502, India for providing facilities. This study is supported by the Department of Science and Technology (Grant No: SR/S2/CMP-0071/2008). D. Madhavi Latha also acknowledges the financial support of DST-WOS-A through grant No.SR/WOS-A/PS-05/2010. P. R. Alapati is thankful to CSIR, New Delhi for their financial support.
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Pardhasaradhi, P., Madhavi Latha, D., Datta Prasad, P.V. et al. Phase transition studies in symmetric dimeric liquid crystals. J Therm Anal Calorim 111, 1483–1490 (2013). https://doi.org/10.1007/s10973-012-2504-2
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DOI: https://doi.org/10.1007/s10973-012-2504-2