Effect of Pyridine on the Mesophase of Teraryl Liquid Crystals: A New Series of Nematic Liquid Crystals Named 2-(4-Alkoxybiphen-4′-yl)-5-methylpyridines
Abstract
:1. Introduction
2. Results and Discussion
2.1. Synthesis
2.2. Thermotropic Studies
- The geometrically asymmetric effect of pyridine moiety favors the formation of nematic phase when alkyl chain lengths are short, but the effect will be obscured when alkyl chain lengths are long and smectic phase appears.
- The distorted hexagonal pyridine moiety will reduce melting and freezing temperatures. The effect is pronounced when alkoxy chains are short and even, and is somewhat obscured when alkoxy chains are long.
- An enlarged effect of pyridine can be found using quinoline moiety, which substantially increase the TNI (or TIN) and reduce the melting and freezing transition temperature, thus providing a wide nematic phase length.
- When pyridine situated in the middle of the teraryl mesogenic core, the nematic phase is favored when alkyl chains are short, and nematic phase length is enlarged because of reduced melting point, however, smectic phases are favored, and polymorphism will be observed when alkyl chains are long.
3. Experimental Section
3.1. General
3.2. Synthesis
Representative Procedure for Homologs of 2-(4-Alkoxybiphen-4′-yl)-5-methylpyridines (nO-PPPyMe, n = 3–8)
4. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interests
References
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Entry (n) | Alkyl Group | Yield a (%) |
---|---|---|
3 | Propyl | 36 |
4 | Butyl | 37 |
5 | Pentyl | 34 |
6 | Hexyl | 36 |
7 | Heptyl | 35 |
8 | Octyl | 38 |
Compound nO-PPPyMe (n) | Phase Transition Temperatures (°C) and Their Corresponding Transition Enthalpies (kJ·mol−1) | |
---|---|---|
Heating | Cooling | |
3 | Cr 203.8(21.41) N 232.8(0.79) I | I 231.2(0.74) N 196.0(21.10) Cr |
4 | Cr 197.0(20.89) N 232.9(0.78) I | I 231.2(0.87) N 186.9(20.55) Cr |
5 | Cr 185.9(19.07) N 220.9(0.95) I | I 219.1(1.00) N 181.1(18.58) Cr |
6 | Cr 175.0(10.97) N 217.6(0.67) I | I 216.0(0.59) N 171.8(9.70) Cr |
7 | Cr 172.1(10.95) N 209.9(0.59) I | I 208.0(0.55) N 169.0(9.62) Cr |
8 | Cr 168.9(10.25) N 206.9(0.80) I | I 205.2(0.78) N 165.7(10.10) Cr |
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Chia, W.-L.; Huang, Y.-S. Effect of Pyridine on the Mesophase of Teraryl Liquid Crystals: A New Series of Nematic Liquid Crystals Named 2-(4-Alkoxybiphen-4′-yl)-5-methylpyridines. Int. J. Mol. Sci. 2016, 17, 344. https://doi.org/10.3390/ijms17030344
Chia W-L, Huang Y-S. Effect of Pyridine on the Mesophase of Teraryl Liquid Crystals: A New Series of Nematic Liquid Crystals Named 2-(4-Alkoxybiphen-4′-yl)-5-methylpyridines. International Journal of Molecular Sciences. 2016; 17(3):344. https://doi.org/10.3390/ijms17030344
Chicago/Turabian StyleChia, Win-Long, and Yu-Sin Huang. 2016. "Effect of Pyridine on the Mesophase of Teraryl Liquid Crystals: A New Series of Nematic Liquid Crystals Named 2-(4-Alkoxybiphen-4′-yl)-5-methylpyridines" International Journal of Molecular Sciences 17, no. 3: 344. https://doi.org/10.3390/ijms17030344