Surface tension of liquid crystals containing two perfluoroalkyl tails

Langmuir

Volumn 13, Issue 24, 1997, Pages 6357-6359

  Mach, P ^a   Huang, C C ^a   Nguyen, H T ^b  

^a University of Minnesota   (United States)

^b CENTRE DE RECHERCHE PAUL PASCAL   (France)

Author keywords

[No Author keywords available]

Indexed keywords

FLUORINE COMPOUNDS; MOLECULAR STRUCTURE; SURFACE TENSION;

PERFLUOROALKYL TAILS;

LIQUID CRYSTALS;

EID: 0031274719     PISSN: 07437463     EISSN: None     Source Type: Journal    
DOI: 10.1021/la970907j     Document Type: Article

References (25)

1. Young, T. In Miscellaneous Works; Peacock, G., Ed.; Murray: London, 1855; p 1. Gibbs, J. W. Collected Works; Longmans, Green: New York, 1906; Dover: New York, 1961; Vol. 1.
2. Young, T. In Miscellaneous Works; Peacock, G., Ed.; Murray: London, 1855; p 1. Gibbs, J. W. Collected Works; Longmans, Green: New York, 1906; Dover: New York, 1961; Vol. 1.
3. Zisman, W. A. Adv. Chem. Ser. 1964, No. 43, 1.
4. Chaudhury, M. K.; Whitesides, G. M. Langmuir 1991, 7, 1013 and references found therein.
5. Mach, P.; Grantz, S.; Debe, D. A.; Stoebe, T.; Huang, C. C. J. Phys. II 1995, 5, 217.
6. Lobko, T. A.; Ostrovskii, B. I.; Pavluchenko, A. I.; Sulianov, S. N. Liq. Cryst. 1993, 15, 361.
7. Clark, N. A.; Lagerwall, S. T. Appl. Phys. Lett. 1980, 36, 899. Epstein, K. A.; Keyes, M. P.; Radcliffe, M. D.; Snustad, D. C. U.S. Patent No. 5417883, 1995.
8. Clark, N. A.; Lagerwall, S. T. Appl. Phys. Lett. 1980, 36, 899. Epstein, K. A.; Keyes, M. P.; Radcliffe, M. D.; Snustad, D. C. U.S. Patent No. 5417883, 1995.
9. Liu, H.; Nohira, H. Liq. Cryst. 1997, 22, 217. Tournilhac, F. G.; Bosio, L.; Simon, J.; Blinov, L. M.; Yablonsky, S. V. Liq. Cryst. 1993, 14, 405. Nguyen, H. T.; Sigaud, G.; Achard, M. F.; Hardouin, F.; Twieg, R. J.; Betterton, K. Liq. Cryst. 1991, 10, 389.
10. Liu, H.; Nohira, H. Liq. Cryst. 1997, 22, 217. Tournilhac, F. G.; Bosio, L.; Simon, J.; Blinov, L. M.; Yablonsky, S. V. Liq. Cryst. 1993, 14, 405. Nguyen, H. T.; Sigaud, G.; Achard, M. F.; Hardouin, F.; Twieg, R. J.; Betterton, K. Liq. Cryst. 1991, 10, 389.
11. Liu, H.; Nohira, H. Liq. Cryst. 1997, 22, 217. Tournilhac, F. G.; Bosio, L.; Simon, J.; Blinov, L. M.; Yablonsky, S. V. Liq. Cryst. 1993, 14, 405. Nguyen, H. T.; Sigaud, G.; Achard, M. F.; Hardouin, F.; Twieg, R. J.; Betterton, K. Liq. Cryst. 1991, 10, 389.
12. Kromm, P.; Cotrait, M.; Rouillon, J. C.; Barois, P.; Nguyen, H. T. Liq. Cryst. 1996, 27, 121. Kromm, P.; Cotrait, M.; Nguyen, H. T. Liq. Cryst. 1996, 21, 95.
13. Kromm, P.; Cotrait, M.; Rouillon, J. C.; Barois, P.; Nguyen, H. T. Liq. Cryst. 1996, 27, 121. Kromm, P.; Cotrait, M.; Nguyen, H. T. Liq. Cryst. 1996, 21, 95.
14. Miyano, K. Phys. Rev. A 1982, 26, 1820.
15. -3 dyn/cm·layer. However, the agreement between our value of surface tension obtained from thin films of one pure liquid-crystal compound (ref 4) and that from the pendant drop (bulk sample) method (ref 20) leads us to conclude that the linear coefficient α is practically zero, unless one can convincingly argue that the surface tension of thick smectic free-standing films differs from that of a bulk sample without a well-organized layer structure in the interior.
16. Eberhardt, M.; Meyer, R. B. Rev. Sci. Instrum. 1996, 67, 2846.
17. Stoebe, T.; Mach, P.; Huang, C. C. Phys. Rev. E 1994, 49, R3587.
18. Because the temperature window for the Sm-A phase differs somewhat from compound to compound, the temperatures at which we made our measurements on the various listed materials did not exactly coincide. In addition, we should note for completeness that one of the compounds (the n = 4 member of group B) shows no Sm-A phase but rather an analog called Sm-C, in which the molecules within each layer are tilted on average with respect to the layer normal. Using our tensiometer, we have made several studies of the temperature dependence of surface tension, for instance over a 10 K interval in the Sm-A phase of H(10)F(5)MOPP (ref 19). No systematic variation in surface tension was seen within our experimental resolution. We found the same to be true over a 25 K window encompassing the Sm-A to Sm-C transition in a fully hydroalkyl compound, DOBAMBC (2-methylbutyl p-[(p-(n-decyloxy)benzylidene)amino] cinnamate). Thus, although even higher resolution studies of temperature effects on the surface tension of liquid-crystal films remain a very intriguing goal, the categorization of surface tension values in groups A through C above, with the reported uncertainties, is unaffected by temperature considerations.
19. Two representative examples of the hydroalkyl-tailed materials are 65OBC (n-hexyl 4′-(n-pentyloxy)biphenyl-4-carboxylate) and 7O.7 ((4-n-heptyloxy)benzylidene)-4-n-heptylaniline).
20. The uncertainty reported here includes the spread of γ for different liquid-crystal compounds within the group.
21. Other measured compounds belonging in this class include H7F6EPP (films studied were within a 3-11 layer thickness range), H(10)F(5)MOPP (films studied were within a 2-120-layer thickness range), which is the subject of ref 19, and also H(8)F(4,2,1)MOPP.
22. Mol, E. A. L.; Shindler, J. D.; Shalaginov, A. N.; de Jeu, W. H. Phys. Rev. E 1996, 54, 536.
23. As a matter of speculation, and keeping in mind the on-average antiparallel packing discussed above, any tendency in group B materials for overlap of the fluorinated tails across an interior layer interface would result in an effective distancing of hydroalkyl end groups from the films' free surfaces. This might enhance the contribution of the group B compounds' fluorinated tails to the measured surface tension. According to this line of thought, fluorination of the second tail might cause a smaller reduction in surface tension than initially expected. We are hopeful that our continuing research into carefully selected liquid crystals will shed light on the question of how much fluorination is necessary to achieve a particular reduction in surface energy, an issue of significant technological importance.
24. Stoebe, T.; Mach, P.; Grantz, S.; Huang, C. C, Phys. Rev. E 1996, 53, 1662.
25. Krishnaswamy, S.; Shashidhar, R. Mol. Cryst. Liq. Cryst. 1977, 38, 353.