Synthesis and Mesomorphism of Novel Star-Shaped Liquid Crystals Containing Donor-Acceptor Groups

Abstract:

A new class of three-armed star-shaped liquid crystals 5a-5d were synthesized, they used 1,3,5-trihydroxybenzene as a core, ω-[4-(p-ethoxybenzoloxy) phenoxycarbonyalkyl acid (3a, 3b) and ω-[4-(p-nitrobenzoloxy) phenoxycarbonyalkyl acid (3c, 3d) as mesogenic arms. Their chemical structures were confirmed by FTIR and ¹H NMR spectra. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and thermogravimetric analyzer (TG) measurements. The results showed that the three-armed star-shaped liquid crystals exhibited a broad range of liquid crystalline phases at moderate temperature. The mesogenic arm structures obviously affected the phase behavior. As the intermedius alkyl chain of the star-shaped compounds lengthened (from n=4 to n=8), their melting points decreased but mesomorphic temperature ranges increased. The temperatures when 5% weight loss occurred (t_d) were higher than 300°C, which revealed that the synthesized three-armed liquid crystals had a high thermal stability. Threadlike, droplet and schlieren texture, typical of nematic phase can be observed in the liquid crystalline state during heating or cooling process.

• Periodical: Applied Mechanics and Materials (Volumes 395-396)
• Pages: 72-75
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.395-396.72
• Online since: September 2013
• Authors: Dan Shu Yao, Jun He, Guo Hua Li, Qian Xu, Ying Gang Jia, Fan Bao Meng
• Keywords: Donor-Acceptor Group, Nematic Phase, Star-Shaped Liquid Crystal, Synthesis

References

[1] H. Meier, M. Lehmann and H.C. Holst: Tetrahedron, Vol. 60(2004), p.6881.

[2] D.S. Yao, B.Y. Zhang and M. Tian: J. Mol. Struct., Vol. 881(2008), p.83.

[3] X.D. Tang, Q.Z. Zhang and Q.F. Zhou: J. Org. Chem., Vol. 23 (2003), p.100.

[3] S. Kumar and S.K. Gupta: Tetrahedron Lett., Vol. 52 (2011), p.5363.

[4] A. Miniewicz, A. Gniewek and J. Parka: Opt. Mater., Vol. 21(2003), p.605.

[5] K. Sandeep: Liq. Cryst., Vol. 31(2004), p.1037.

[6] A. Belaissaoui, I.M. Saez and S.J. Cowling: Macromolecules, Vol. 46 (2013), p.1268.

[7] G.K. Bong, K. Sehoon and Y.P. Soo: Tetrahedron Lett., Vol. 42 (2001), p.2697.

[8] N. Tamaoki, Y. Aoki, M. Moriyama and M. Kidowaki: Chem. Mater., Vol. 15 (2003), p.719.