Nowadays, liquid crystalline materials are best known for their successful implementation in flat panel displays, and yet they exhibit a plethora of peculiar properties that offer enormous potential for fundamental science as well as innovative applications beyond the displays sphere. The proposal addresses a fast-developing area of liquid crystal science in which bulk, helical arrangements are formed from constituents, which are not themselves chiral.

The current proposal arises from previous work in which it was shown that flexibly linked, dimeric molecules may also exhibit this general behaviour. The project envisages combined experimental, computational and spectroscopic studies that will provide valuable information on structural and electronic factors influencing formation and stability of helical self-assembly and expands the possibility for controlled fabrication of novel materials for various applications ranging from micropower generators to artificial muscle

 

Results:

A comprehensive study of structure/NTB phase correlation of bent-shaped dimers having variant linking groups revealed that the stability of the NTB phase rises with increasing effective molecular bending but also that intramolecular torsion in conjunction with molecular curvature plays essential role in stabilization of the NTB phase. The study of naphthyl-based dimers revealed that π-π interactions affect stability of the NTB phase and a new liquid-crystalline phase was observed which electro-optic response is nematic-like. Investigation of a binary mixture between two NTB nematogens revealed significant extension of the temperature range of the NTB phase, the periodicity in the range of 6-7 nm and induction of the smectic phase which origin can be traced to conformational disorder of terminal chains.

  • T. Ivšić, U. Baumeister, I. Dokli, A. Mikleušević and A. Lesac, “The effect of the structural variations on the incidence of the NTB phase“, Workshop “Twist-Bend Nematics and Beyond”, 7-8 April 2016, Southampton, UK (oral contribution).T. Ivšić, M. Vinković, U. Baumeister, A. Mikleušević, A. Lesac*, “Towards understanding the NTB phase: a combined experimental, computational and spectroscopic study“RSC Adv. 6 (2016) 5000-5007.
  • T. Ivšić, U. Baumeister, I. Dokli, A. Mikleušević, A. Lesac*, “Sensitivity of the NTB Phase Formation to the Molecular Structure of Imino-linked Dimers“, Liquid Crystals 44 (2017) 93-105. 
  • A. Knežević, M. Sapunar, A. Buljan, I. Dokli, Z. Hameršak, D. Kontrec, A. Lesac*, "Fine-tuning effect of p–p interactions on the stability of the NTB phase" Soft Matter14 (2018) 8466-8474, DOI: 10.1039/c8sm01569d
  • A. Lesac*, U. Baumeister, I. Dokli, Z. Hameršak, T. Ivšić, D. Kontrec, M. Viskić, A. Knežević, R. J. Mandle, "Geometric aspects influencing N-NTB transition - implication of intramolecular torsion" Liq. Cryst45 (2018) 1101-1110. DOI: 10.1080/02678292.2018.1453556
  • A. Knežević, I. Dokli, M. Sapunar, S. Šegota, U. Baumeister, A. Lesac*, "Induced smectic phase in binary mixture of twist-bend nematogens" Beilstein J. Nanotechnol. 9 (2018) 1297–1307. doi:10.3762/bjnano.9.122
  • Claire Meyer, Ivan Dozov, Patrick Davidson, Geoffrey R. Luckhurst, Irena Dokli, Anamarija Knezevic, Andreja Lesac, "Electric-field effects in the twist-bend nematic phase", Proc. SPIE 10555, Emerging Liquid Crystal Technologies XIII, 105550Z (8 February 2018); doi: 10.1117/12.2301296.
  • A. Buljan, A. Knežević, I. Dokli, A. Lesac*, ″Synthesis and mesomorphic properties of novel bent-shaped naphthyl diketones″ Croatica Chem Acta 2019 accepted.

Other associates

dr.sc. Irena Dokli

dr.sc. Trpimir Ivšić

dr.sc. Anamarija Knežević

dr.sc. Darko Kontrec

Temperature-controlled powder X-ray analysis in collaboration with dr.sc. Ute Baumeister (Martin Luther University Halle-Wittenberg, Germany)

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