Specific interactions in discotic liquid crystals

Journal of Materials Chemistry

Volumn 13, Issue 3, 2003, Pages 458-469

  Kouwer, Paul H J ^a,b   Jager, Wolter F ^a   Mijs, Wim J ^a   Picken, Stephen J ^a  

^a DELFT UNIVERSITY OF TECHNOLOGY   (Netherlands)

^b UNIVERSITY OF HULL   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ACETYLENE; CHARGE TRANSFER; COMPLEXATION; PHENOLS; SUBSTITUTION REACTIONS;

DISCOTIC LIQUID CRYSTALS;

LIQUID CRYSTAL DISPLAYS;

ACETYLENE; PHENOL DERIVATIVE; POLYMER;

ARTICLE; CHEMICAL INTERACTION; CHEMICAL PARAMETERS; CHEMICAL REACTION; COMPLEX FORMATION; ELECTRON; LIQUID CRYSTAL; MELTING POINT; MOLECULAR INTERACTION; SUBSTITUTION REACTION; TEMPERATURE;

EID: 0037338375     PISSN: 09599428     EISSN: None     Source Type: Journal    
DOI: 10.1039/b208923h     Document Type: Article

References (68)

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4. For a review on discotic liquid crystals read: (a) A. N. Cammidge and R. J. Bushby, in Handbook of Liquid Crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 2B, pp. 693-748; (b) S. Chandrasekhar, in Handbook of liquid crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 2B, pp. 749-780;
5. For a review on discotic liquid crystals read: (a) A. N. Cammidge and R. J. Bushby, in Handbook of Liquid Crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 2B, pp. 693-748; (b) S. Chandrasekhar, in Handbook of liquid crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 2B, pp. 749-780;
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15. (a) J. W. Goodby and G. W. Gray, Handbook of Liquid Crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 1, pp. 17-24;
16. (b) the suffices 'o' and 'd' for 'ordered' and 'disordered' reflect the extent of intracolumnar organisation of the columnar phase with the two extremes of 'o' for long-range positional order and 'd' for one-dimensional liquid-like order. We have used the suffix when we had sufficient X-ray diffraction evidence to choose between one of the two extremes. The suffix was omitted when the diffraction peaks showed intermediate levels of intracolumnar order.
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18. r phase is characterised by a second order phase transition, visible in the DSC diagram. The X-ray diffractogram shows mixed reflections, indicating a three-dimensional positional organisation. Despite the increased viscosity, the sample remains deformable during OPM experiments.
19. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
20. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
21. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
22. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
23. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
24. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
25. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
26. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
27. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
28. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
29. For reports on polymers bearing disc-shaped mesogens as a side-chain, see: (a) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2000, 33, 4336-4342; (b) D. Stewart, G. S. McHattie and C. T. Imrie, J. Mater. Chem., 1998, 8, 47-51; (c) M. Weck, B. Mohr, B. R. Maughon and R. H. Grubbs, Macromolecules, 1997, 30, 6430-6437; (d) N. Boden, R. J. Bushby and Z. B. Lu, Liq. Cryst., 1998, 25, 47-58; (e) W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1983, 4, 807-815; (f) for reports on polymers bearing disc-shaped mesogens in the main-chain, see: O. Herrmann-Schönherr, J. H. Wendorff, W. Kreuder and H. Ringsdorf, Makromol. Chem., Rapid Commun., 1986, 7, 97-101; (g) G. Wenz, Makromol. Chem., Rapid Commun., 1985, 6, 577-584; (h) N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock, J. Mater. Chem., 1995, 5, 2275-2281; (i) for reports on macromolecular networks bearing disc-shaped mesogens, see: C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143-6149; (j) S. Disch, H. Finkelmann, H. Ringsdorf and P. Schuhmacher, Macromolecules, 1995, 28, 2424-2428; (k) C. D. Braun and J. Lub, Liq. Cryst., 1999, 26, 1501-1509.
30. (a) P. H. J. Kouwer, J. Gast, W. F. Jager, W. J. Mijs and S. J. Picken, Mol. Cryst. Liq. Cryst., 2001, 364, 225-234;
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32. (a) Complexes of an electron-rich donor with an electron rich acceptor, showing an induced absorption band, are often referred to as charge transfer complexes. However, it should be stressed that the attractive interaction between these molecules is rather a combination of van der Waals, quadrupolar and charge transfer interactions. For the sake of clarity, in this contribution the name charge transfer complex is used to describe the total sum of interactions. For a review on charge transfer complexing in discotic liquid crystals read;
33. (b) K. Praefcke and D. Singer, Handbook of Liquid Crystals, ed. D. Demus, J. W. Goodby, G. W. Gray, H. W. Spiess and V. Vill, Wiley-VCH, New York, 1998, part 2B, pp. 945-967;
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38. The materials are abbreviated according to the length of the alkyl group (n) and the nature of the linking group (X), i.e. nX-D, where X = Am for the amide substituted mesogen.
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40. During the five-fold coupling reaction, the phenylacetylene with an electron withdrawing group is consumed more rapidly than the corresponding acetylene with an electron donating group, although no traces of product could be detected. Since the reaction proceeds in an argon atmosphere, oxidative dimerisation can be excluded. NMR analysis indicates a complex mixture of aromatic groups.
41. o > 0). For disk-shaped liquid crystals, the birefringence is usually negative, making discotics very suitable for application as compensation layers in display technology;
42. (b) only recently, the first example of a room temperature nematic phase obtained from disk-shaped liquid crystals was observed in a discotic liquid crystal based on a hexakis(phenylethynyl)benzene core and substituted with rac-4-methylnonyl tails, resulting in a broad distribution of stereoisomers: S. Kumar and S. K. Varhney, Angew. Chem., Int. Ed., 2000, 39, 3140-3142.
43. (a) P. H. J. Kouwer, O. van den Berg, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2002, 35, 2576-2582;
44. (b) P. H. J. Kouwer, W. F. Jager, W. J. Mijs and S. J. Picken, Macromolecules, 2002, 35, 4322-4329.
45. The forming optical texture was observed after quickly heating the sample to 300 °C followed by cooling to 250 °C. Despite the degradation process (especially on the edges of the sample between the microscope slides) growing hexagons were clearly observed, indicative of a columnar hexagonal mesophase. By this method a clearing temperature of 280 °C was estimated.
46. The drawn curve was taken from a previous publication (see ref. 11b) and was calculated from fitting the series of alkyl-substituted polymers to a power-law.
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54. (b) D. Guillon, A. Skoulios, C. Piechocki, J. Simon and P. Weber, Mol. Cryst. Liq. Cryst., 1983, 100, 275-284;
55. (c) I. Cho and Y. Lim, Mol. Cryst. Liq. Cryst., 1988, 154, 9-26.
56. In a recent publication (ref. 19a) we described some very disordered columnar materials, as determined by XRD, and even these exhibited quite 'normal' latent heat values.
57. The exception is the series of six-fold substituted alkylsulfonylbenzenes in: K. Praefcke, W. Poules, B. Schleube, R. Poupko and Z. Luz, Z. Naturforsch. B, 1984, 39, 950. No liquid crystalline properties were detected in alkylsulfonyl substituted triphenylenes.
58. The use of amide bonds in combination with steric repulsion can yield highly ordered columnar phases, which may be applied as molecular wires, for example: (b) M. L. Bushey, A. Hwang, P. W. Stephens and C. Nuckolls, J. Am. Chem. Soc., 2001, 123, 8157-8158 and references therein.
59. Some experiments have been performed to decrease the number of H-bonds, e.g. by preparing the meta-amide-substituted derivative of 6Am-D. It was anticipated that the number of hydrogen bonds was strongly reduced by assuming a random orientation of the amide group. Indeed, the material obtained showed a stable columnar mesophase, but unfortunately, we were not able to purify the material to the high level that is required for a good analysis of the liquid crystalline properties.
60. Complexes with a TNF mol fraction higher than 0.6 were unstable and show macroscopic phase separation. In contact samples between 60-D and TNF, as studied with OPM, it could clearly be observed that TNF was immiscible with the CT complex.
61. M. W. C. P. Franse, unpublished results.
62. The formation of charge transfer complexes between materials based on the pentakis(phenylethnyl)phenoxy core and TNF derivatives is easily recognised by the formation of a charge transfer band in the absorption spectrum of the complex. The complexes are usually orange (weak complex) to dark red (strong complex) compared to (pale) yellow constituents.
63. hd phase.
64. For studies on the length of spacer, originating from the central core of the disc, see: (a) K. Praefcke, D. Singer, M. Langner, B. Kohne, M. Ebert, A. Liebmann and J. H. Wendorff, Mol. Cryst. Liq. Cryst., 1992, 215, 121-126; (b) H. Bengs, O. Karthaus, H. Ringsdorf, C. Baehr, M. Ebert and J. H. Wendorff, Liq. Cryst., 1991, 10, 161-168.
65. For studies on the length of spacer, originating from the central core of the disc, see: (a) K. Praefcke, D. Singer, M. Langner, B. Kohne, M. Ebert, A. Liebmann and J. H. Wendorff, Mol. Cryst. Liq. Cryst., 1992, 215, 121-126; (b) H. Bengs, O. Karthaus, H. Ringsdorf, C. Baehr, M. Ebert and J. H. Wendorff, Liq. Cryst., 1991, 10, 161-168.
66. For studies of CT complexes with acceptors similar in size, but different in electron affinity, see: (a) R. Wüstefeld, Ph.D. Thesis, Johannes Gutenberg Universität, Mainz, Germany 1990; (b) M. Ebert, Ph.D. Thesis, Technische Hochschule Darmstadt, Darmstadt, Germany, 1990.
67. For studies of CT complexes with acceptors similar in size, but different in electron affinity, see: (a) R. Wüstefeld, Ph.D. Thesis, Johannes Gutenberg Universität, Mainz, Germany 1990; (b) M. Ebert, Ph.D. Thesis, Technische Hochschule Darmstadt, Darmstadt, Germany, 1990.
68. R. Elsässer, G. H. Mehl, J. W. Goodby and M. Veith, Angew. Chem., Int. Ed., 2001, 40, 2688-2690 and references therein.