Communication
Electric-Field Modulation of Component Exchange in Constitutional Dynamic Liquid Crystals†
Nicolas Giuseppone Dr.,
Jean-Marie Lehn Prof. Dr.,
Nicolas Giuseppone Dr.
Institut de Science et d'Ingénierie Supramoléculaires, 8 Allée Gaspard-Monge, BP 70028, 67083 Strasbourg, France, Fax: (+33) 390-245-140
Search for more papers by this authorJean-Marie Lehn Prof. Dr.
Institut de Science et d'Ingénierie Supramoléculaires, 8 Allée Gaspard-Monge, BP 70028, 67083 Strasbourg, France, Fax: (+33) 390-245-140
Search for more papers by this authorNicolas Giuseppone Dr.,
Jean-Marie Lehn Prof. Dr.,
Nicolas Giuseppone Dr.
Institut de Science et d'Ingénierie Supramoléculaires, 8 Allée Gaspard-Monge, BP 70028, 67083 Strasbourg, France, Fax: (+33) 390-245-140
Search for more papers by this authorJean-Marie Lehn Prof. Dr.
Institut de Science et d'Ingénierie Supramoléculaires, 8 Allée Gaspard-Monge, BP 70028, 67083 Strasbourg, France, Fax: (+33) 390-245-140
Search for more papers by this author†
We thank Dr. Jean-Louis Schmitt for checking the experimental results. We are grateful to Dr. Daniel Guillon, Dr. Jacques Malthête, and Dr. Jacques Prost for their constructive remarks on the manuscript.
Graphical Abstract
Playing the field: Application of an electric field to the thermodynamic equilibria of constitutionally dynamic sets of imines and amines that contain an imine with liquid-crystalline properties and a negative dielectric anisotropy leads to the amplification of the constituent that couples most strongly to the electric field, namely the liquid crystal (LC, see example). The field can thus induce a liquid to nematic phase transition.
References
- 1
- 1aJ.-M. Lehn, Chem. Eur. J. 1999, 5, 2455;
10.1002/(SICI)1521-3765(19990903)5:9<2455::AID-CHEM2455>3.0.CO;2-H CAS Web of Science® Google Scholar
- 1bR. L. Cousins, S. A. Poulsen, J. K. M. Sanders, Curr. Opin. Chem. Biol. 2000, 4, 270;
- 1cS. J. Rowan, S. J. Cantrill, G. R. L. Cousins, J. K. M. Sanders, J. F. Stoddart, Angew. Chem. 2002, 114, 938;
10.1002/1521-3757(20020315)114:6<938::AID-ANGE938>3.0.CO;2-K Google ScholarAngew. Chem. Int. Ed. 2002, 41, 898.10.1002/1521-3773(20020315)41:6<898::AID-ANIE898>3.0.CO;2-E CAS PubMed Web of Science® Google Scholar
- 2
- 2aJ.-M. Lehn, Proc. Natl. Acad. Sci. USA 2002, 99, 4763;
- 2bJ.-M. Lehn, Science 2002, 295, 2400.
- 3O. Ramström, J.-M. Lehn, Nat. Rev. Drug Discovery 2001, 1, 26.
- 4
- 4aN. Giuseppone, J.-M. Lehn, Chem. Eur. J. 2006, 12, 1715;
- 4bN. Giuseppone, J.-M. Lehn, J. Am. Chem. Soc. 2004, 126, 11448;
- 4cN. Giuseppone, G. Fuks, J.-M. Lehn, Chem. Eur. J. 2006, 12, 1723.
- 5S. Nampally, J.-M. Lehn, Proc. Natl. Acad. Sci. USA 2005, 102, 5938.
- 6N. Giuseppone, J.-L. Schmitt, J.-M. Lehn, Angew. Chem. 2004, 116, 5010;
10.1002/ange.200460343 Google ScholarAngew. Chem. Int. Ed. 2004, 43, 4902.
- 7J.-M. Lehn in Supramolecular Science: Where It Is and Where It Is Going (Eds.: ), Kluwer, Dordrecht, The Netherlands, 1999, 287.
- 8J.-M. Lehn, Polym. Int. 2002, 51, 825, and references therein.
- 9For a recent review on the use of liquid crystals for display technology, see: P. Kirsch, M. Bremer, Angew. Chem. 2000, 112, 4384;
10.1002/1521-3757(20001201)112:23<4384::AID-ANGE4384>3.0.CO;2-S Google ScholarAngew. Chem. Int. Ed. 2000, 39, 4216.10.1002/1521-3773(20001201)39:23<4216::AID-ANIE4216>3.0.CO;2-K CAS PubMed Web of Science® Google Scholar
- 10P.-G. de Gennes, The Physics of Liquid Crystals Clarendon, Oxford, 1973.
- 11
- 11aC.-P. Fan, M. J. Stephen, Phys. Rev. Lett. 1970, 25, 500;
- 11bI. Lelidis, M. Nobili, G. Durand, Phys. Rev. E 1993, 48, 3818;
- 11cI. Lelidis, G. Durand, Phys. Rev. E 1993, 48, 3822;
- 11dI. Lelidis, G. Durand, Phys. Rev. Lett. 1994, 73, 672;
- 11eI. Lelidis, G. Durand, Phys. Rev. Lett. 1996, 76, 1868.
- 12
- 12aJ. Tang, S. Fraden, Phys. Rev. Lett. 1993, 71, 3509;
- 12bM. I. Boamfǎ, K. Viertler, A. Wewerka, F. Stelzer, P. C. M. Christianen, J. C. Maan, Phys. Rev. E 2003, 67, 050701.
- 13
- 13aTo improve the reliability of LC displays, some studies addressed the influence of traces of water in mixtures of imine-type liquid crystals.[13b] The presence of residual water was demonstrated, as well as subsequent changes in the TI/N values of the mixtures; however, the use of mixtures of LCs as dynamic systems, has not been explored;
- 13bH. Sorkin, A. Denny, RCA Rev. 1973, 34, 308.
- 14The choice of transimination as the exchange reaction is of crucial importance to avoid the presence of water (that would be formed in amine–carbonyl condensations) in the present systems so as to maintain high resistance to the electric current upon application of a high voltage. For catalyzed and noncatalyzed transimination reactions, see: N. Giuseppone, J.-L. Schmitt, E. Schwartz, J.-M. Lehn, J. Am. Chem. Soc. 2005, 127, 5528, and references therein.
- 15
- 15aUnder these conditions the heating appeared negligible (ca. 1 °C measured at the surface of the ITO plates), in agreement with literature results:
- 15bW. Helfrich, Phys. Rev. Lett. 1970, 24, 201;
- 15cA. J. Nicastro, P. H. Keys, Phys. Rev. A 1981, 30, 3156.
- 16G. H. Heilmeier, L. A. Zoanoni, L. A. Barton, Appl. Phys. Lett. 1968, 13, 46.
- 17The rate of the reaction in a CDCl3 solution (C=3.84 M) was found to be t1/2=60 min at 22.5 °C and t1/2=30 min at 30 °C, which is also suitable for NMR measurements.
- 18The change in the direction of the displacement of the equilibrium above 30 °C (Figure 3 B, right-hand part of the curve) was found to arise from evaporation of cyclopentylamine. Thus, the effect of heating on the equilibrium is in the opposite direction (left-hand part of the curve, Figure 3 B) than that caused by the field before evaporation takes over.
- 19For example, the use of a molar ratio of MBBA:cyclopentanol of 55:45 leads to an evaporation of 7.5 % of the cyclopentanol without field, and of 38.5 % with a field of 3.5×104 V cm−1, after 18 h at 23 °C. Moreover, if MBBA is replaced by pentaethylene glycol (with no liquid-crystal properties and similar viscosity), no differential evaporation was observed.
- 20The effect amounts to a sort of purification under high voltage; for electrohydrodynamic effects in the MBBA-type nematic phases, see: D. Jin, H. Kim, S. H. Kim, S. K. Kim, J. Phys. Chem. B 1997, 101, 10757.
- 21The coexistence between liquid-crystalline and liquid domains is observed between the ITO plates.
- 22S. Dhara, N. V. Madhusudana, Europhys. Lett. 2004, 67, 411.
- 23For a theoretical study of the effect of an external electric field on bond activation reactions, see: S. Shaik, S. P. de Visser, D. Kumar, J. Am. Chem. Soc. 2004, 126, 11746.
- 24We thank a referee for comments concerning the origin of the chemical effects observed by application of the electric field. In particular, the “coupling to the field” merely indicates that the observed effects result from the interaction of the electric field with the liquid-crystalline species. Such coupling may involve several factors/mechanisms. The energy necessary to displace the equilibrium as described in Scheme 2 and Figure 4 is calculated to be about ΔΔG≈80 cal mol−1. The electric interaction energy with the system is too weak to explain the observations, even if a contribution from flexoelectricity[10] is taken into account. When the field is applied close to the phase transition, the effect could be in the correct range, but should change on varying the temperature, which appears not to be the case. The heat capacity associated with the isotropic/nematic phase transition is known to be also in the range required to shift the equilibrium,[25] however, the lack of a temperature effect (Figure 5) indicates that it is not a major factor. Finally, electrohydrodynamic instabilities observed in the DSM mode are known to be caused by ionic currents;[26] the contribution of the field heterogeneity related to the motions of ionic particles throughout the sample could be more than enough to displace the equilibrium with the experimentally measured values of the conductivity. Ionic motions and the conceivable accumulation of charges on the electrode surfaces would lead to high local field values, capable of sufficient interaction with the liquid crystal to result in its amplification from the DCL.
- 25R. Chang, F. B. Jones, J. J. Ratto, Mol. Cryst. Liq. Cryst. 1976, 33, 13 (ΔH(Nematic−Isotropic)=0.10 kcal mol−1; T=45.8 °C).
- 26aE. F. Carr, Mol. Cryst. Liq. Cryst. 1969, 7, 253;
- 26bW. Helfrich, J. Chem. Phys. 1969, 51, 4093;
- 26cS. Hirata, T. Tako, Jpn. J. Appl. Phys. Part 2 1982, 21, L607;
- 26dS. J. Tavener, T. Mullin, G. I. Blake, K. A. Cliffe, Phys. Rev. E 2000, 63, 011708.
