Abstract

Çalışmada dimerik yapıda moleküllerde ve ötektik karışımlarda sıklıkla kullanılmakta olan siyanobifenil gurubuna ait 3OCB sıvı kristalinin bazı fiziksel özellikleri incelenmiştir. Bu bağlamda, farklı sıcaklık bölgelerinde optik özellikleri incelenmiştir. Optik ölçümler sonucu 3OCB’nin monotropik mezofaz sergilediği tespit edilmiştir ve söz konusu mezofazın faz aralığı belirlenmiştir. Bununla birlikte, sıvı kristalin izotropik faz-nematik mezofaz geçiş bölgesinde heterofaz alanı ortaya çıktığı gözlenmiştir. Mezofaz bölgesinin ve heterofaz alanının morfolojik analizi de gerçekleştirilmiştir. Ayrıca, kalorimetrik ölçümler gerçekleştirilerek yığın halde ilgili sıvı kristalin faz aralığının nasıl değiştiği optik ölçümlerden elde edilen sonuçlar ile kıyaslanmıştır. Kızılötesi spektroskopik ölçümler gerçekleştirilerek 3OCB’nin baskın titreşim bantları hakkında bilgiler edinilmiştir. Endüstride ve bilimsel çalışmalarda sıklıkla kullanılan 3OCB’nin kızılötesi spektroskopisi gerçekleştirilerek molekülün fonksiyonel gurupları ve yapısı hakkında bilgi edinilmesi sağlanmıştır.

Keywords

• Sıvı kristaller
• monotropik mezofaz
• optik
• DSC
• FT-IR

STUDY ON PHASE TRANSITION FEATURES AND INFRARED SPECTROSCOPY OF 3OCB LIQUID CRYSTAL

Abstract

In the study, some physical properties of the 3OCB liquid crystal belonging to the cyanobiphenyl group, which is frequently used in dimeric molecules and eutectic mixtures, were investigated. In this context, its optical properties in different temperature interval have been investigated. As a result of optical measurements, it was determined that 3OCB exhibited a monotropic mesophase and that the phase range of the mesophase was determined. In addition, it was observed that a heterophase region appeared in the liquid crystalline isotropic phase-nematic mesophase transition. Morphological analysis of the mesophase and heterophase region was also performed. Also, by performing calorimetric measurements, how the relevant liquid crystal phase interval changes in bulk state was compared with the results obtained from optical measurements. Information about the 3OCB's dominant vibration bands was obtained by performing infrared spectroscopic measurements. The infrared spectroscopy of 3OCB, which is frequently used in industry and scientific studies, has been performed to provide information about the functional groups and structure of the molecule.

Keywords

• Liquid crystals
• monotropic mesophase
• optic
• DSC
• FT-IR

Thanks

The author would like to acknowledge the technical support of The Center of Research Laboratories, Muğla Sıtkı Koçman University.

References

1. Oswald, P. and Pieranski, P. Smectic and Columnar Liquid Crystals, Taylor & Francis, Boca Raton, 711s., 2005.
2. Demus, D., Goodby, J., Gray, G.W., Spiess, H. ‐W., and Vill, V., Handbook of Liquid Crystals, Wiley-VCH, Weinheim, 2591s. 1998.
3. Collings, P.J. and Hird, M., Introduction to liquid crystals: Chemistry and physics, Taylor & Francis, London, 317s., 2017
4. Onusseit, H Stegmeyer, H. “Investigations Of Phase Diagrams with Monotropic Liquid-Crystalline Phases”, Thermochimica Acta, 83, 145–152, 1985.
5. Onusseit, H. and Stegemeyer, H., “Phase Diagrams of Eutectic Mixed Systems with Monotropic Liquid-Crystalline Phases”, Molecular Crystals and Liquid Crystals. 111 (1–2), 31–43., 1984.
6. Jungbauer, D. and Wendorff, J.H., “Electro-Optical Studies on Monotropic Nematic-Smectic Phase Transitions”, Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics, 170 (1), 159–177, 1989.
7. Šakalyte, A., Giamberini, M., and Reina, J.A., “Synthesis and characterisation of a monotropic dendritic liquid crystalline aziridine monomer”, Liquid Crystals. 41 (2), 153–162, 2014.
8. Ahmed, H.A. “Mesophase stability in binary mixtures of monotropic nematogens”, Liquid Crystals. 42 (1), 70–80, 2015.

9. Grunwald, M.A., Haenle, J.C., Kreß, K.C., Forschner, R., Wöhrle, T., Frey, W., et al. “Mesomorphic properties of cyanobiphenyl dimers with a central malonate unit”, Liquid Crystals, 45(11), 1626-1636, 2018.
10. Paterson, D.A., Crawford, C.A., Pociecha, D., Walker, R., Storey, J.M.D., Gorecka, E., et al., “The role of a terminal chain in promoting the twist-bend nematic phase: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4′-yl)-6-(4-alkyloxyanilinebenzylidene-4′-oxy)hexanes”, Liquid Crystals, 45(13-15), 2341-2351, 2018.
11. Wang, K., Jirka, M., Rai, P., Twieg, R.J., Szilvási, T., Yu, H., et al., “Synthesis and properties of hydroxy tail-terminated cyanobiphenyl liquid crystals”, Liquid Crystals, 46(3), 397-407, 2019.
12. Wang, K., Rai, P., Fernando, A., Szilvási, T., Yu, H., Abbott, N.L., et al., “Synthesis and properties of fluorine tail-terminated cyanobiphenyls and terphenyls for chemoresponsive liquid crystals”, Liquid Crystals, 47(1), 3-16, 2020.
13. Paterson, D.A., Abberley, J.P., Harrison, W.T.A., Storey, J., and Imrie, C.T., “Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase”, Liquid Crystals, 44(1), 127-146, 2017.
14. Sharma, D. and Nath Tiwari, S., “Molecular Structure and Vibrational Dynamics Studies of 4-n-propyl-4′-cyanobiphenyl using Ab initio and DFT Methods”, Materials Today: Proceedings. 5 (7), 15325–15334, 2018.
15. Babkov, L.M., Davydova, N.I., Puchkovskaya, G.A., and Khakimov, I.N., “IR absorption spectra and structure of 4-cyano-4′,-p-alkoxybiphenyls”, Journal of Structural Chemistry, 34, 92–97, 1993.
16. Sharma, D., Tiwari, G., and Tiwari, S.N., “Thermodynamical properties and infrared spectra of 4-n-propoxy-4’- cyanobiphenyl: Hartree-Fock and density functional theory methods”, International Journal of Electroactive Materials, 5 (2), 19–30, 2017.
17. Giricheva, N.I., Fedorov, M.S., Shpilevaya, K.E., Syrbu, S.A., and Ditsina, O.Y., “Characteristics of the hydrogen bond and the structure of Н-complexes of p-n-propyloxybenzoic acid and p-n-propyloxy-p′-cyanobiphenyl”, Journal of Structural Chemistry, 58 (1), 9–16, 2017.
18. Kuz’mina, L.G., Kucherepa, N.S., and Churakov, A. V., “Mesophase design: II. Molecular structure and crystal packing of 4-alkyloxycyanobiphenyls”, Crystallography Reports, 57 (2), 213–226, 2012.
19. Dierking, I., Textures of Liquid Crystals, WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim, 233s, 2003.
20. Różycka, A., Deptuch, A., Jaworska-Gołąb, T., Węgłowska, D., and Marzec, M., “Evidence of monotropic hexatic tilted smectic phase in the phase sequence of ferroelectric liquid crystal” Phase Transitions, 91 (2), 159–169, 2018.
21. Blinov, L.M., Structure and Properties of Liquid Crystals, Springer, Dordrecht, Heidelberg, London, New York, 458s, 2011.
22. Doi, M. Soft Matter Physics, Oxford University Press. Oxford, 270s, 2013.
23. Kleman, M. and Lavrentovich, O.D., Soft Matter Physics: An Introduction, Springer New York, New York, NY, 664s, Eds. 2004.
24. Mamuk, A.E. and Nesrullajev, A., “Peculiarities of thermo-morphologic and thermotropic transformations of heterophase regions: nematic ↔ isotropic phase transition in 4-n-Alkyl-4’-cyanobiphenyl mesogens”, Journal of Optoelectronics and Advanced Materials. 21 (11–12), 691-697, 2019. Nesrullajev, A., Avci, N., and Oktik, Ş., “Peculiarities of biphasic regions at phase transitions in oriented textures of 4-cyano-4′-n-pentylbiphenyl”, Physics Letters, Section A: General, Atomic and Solid State Physics, 364 (6), 510–514, 2007.
25. Smith, G.W., “Study of Formation, Phase Behavior, and Microdroplet Size of a Polyurethane-based Polymer-dispersed Liquid Crystal”, Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics, 180 (2), 201–222, 1990.
26. Smith, G.W. and Vaz, N.A., “The relationship between formation kinetics and microdroplet size of epoxy-based polymer-dispersed liquid crystals”, Liquid Crystals, 3 (5), 543–571, 1988.
27. Alexe-Ionescu, A.L., Barberi, R., Bonvent, J.J., and Giocondo, M., “Nematic surface transitions induced by anchoring competition”, Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 54 (1), 529–535, 1996.
28. Martínez-Felipe, A., Imrie, C.T., and Ribes-Greus, A., “Study of structure formation in side-chain liquid crystal copolymers by variable temperature fourier transform infrared spectroscopy”, Industrial and Engineering Chemistry Research, 52 (26), 8714–8721, 2013.
29. Singh, S., Singh, H., Srivastava, A., Tandon, P., Deb, R., Debnath, S., et al., “Study of phase transitions in a bent-core liquid crystal probed by infrared spectroscopy”, Vibrational Spectroscopy, 86, 24–34., 2016.
30. Osiecka, N., Galewski, Z., Juszyńska-Gałązka, E., and Massalska-Arodź, M., “Studies of reorganization of the molecules during smectic A–smectic C phase transition using infrared spectroscopy and generalized two-dimensional correlation analysis”, Journal of Molecular Liquids, 224, 677–683, 2016.
31. Avadanei, M., Perju, E., Cozan, V., and Bruma, M., “Phase transitions of a monotropic azomethine liquid crystal investigated by ATR-FTIR spectroscopy”, Phase Transitions, 87 (3), 243–254, 2014.