Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Shear-induced molecular precession in a hexatic Langmuir monolayer

Nature volume 410, pages 348–351 (2001)Cite this article

Abstract

Liquid crystalline behaviour is generally limited to a select group of specially designed bulk substances. By contrast, it is a common feature of simple molecular monolayers and other quasi-two-dimensional systems1, which often possess a type of in-plane ordering that results from unbinding of dislocations—a ‘hexatic’ liquid crystalline phase. The flow of monolayers is closely related to molecular transport in biological membranes, affects foam and emulsion stability and is relevant to microfluidics research. For liquid crystalline phases, it is important to understand the coupling of the molecular orientation to the flow. Orientationally ordered (nematic) phases in bulk liquid crystals exhibit ‘shear aligning’ or ‘tumbling’ behaviour under shear, and are described quantitatively by Leslie–Ericksen theory2. For hexatic monolayers, the effects of flow have been inferred from textures of Langmuir–Blodgett films3,4,5 and directly observed at the macroscopic level6,7,8,9,10. However, there is no accepted model of hexatic flow at the molecular level. Here we report observations of a hexatic Langmuir monolayer that reveal continuous, shear-induced molecular precession, interrupted by occasional jump discontinuities. Although superficially similar to tumbling in a bulk nematic phase, the kinematic details are quite different and provide a possible mechanism for domain coarsening and eventual molecular alignment in monolayers. We explain the precession and jumps within a quantitative framework that involves coupling of molecular orientation to the local molecular hexatic ‘lattice’, which is continuously deformed by shear.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Hexatic and nematic phase representations.
Figure 2: Continuous change in the reflectivity of domains in a docosanoic acid (CH3(CH2)20COOH) monolayer in the L2′ phase. (Π = 23 mN m-1).
Figure 3: Evolution of the 8-bit digitized reflectivity for three different domains under three different shear flows.
Figure 4: Jump discontinuities are revealed in the reflectivity of two domains from different experiments shearing a monolayer in the L2′ phase.
Figure 5: Geometrical model for the onset and magnitude of the jump discontinuities in the evolution of ϕ( t ).

Similar content being viewed by others

References

  1. Halperin, B. I. & Nelson, D. R. Theory of two-dimensional melting. Phys. Rev. Lett. 41, 121–124 (1978).

    Article  ADS  MathSciNet  CAS  Google Scholar 

  2. Chandrasekhar, S. Liquid Crystals 2nd edn (Cambridge Univ. Press, Cambridge/New York, 1992).

    Book  Google Scholar 

  3. Peterson, I. R. Optical observation of monomer Langmuir-Blodgett film structure. Thin Solid Films 116, 357–365 (1984).

    Article  ADS  CAS  Google Scholar 

  4. Leuthe, A. & Riegler, H. Thermal behaviour of Langmuir-Blodgett films. II. X-ray and polarized reflection microscopy studies on coexisting polymorphism, thermal annealing and epitaxial layer growth of behenic acid multilayers. J. Phys. D 25, 1786–1797 (1992).

    Article  ADS  CAS  Google Scholar 

  5. Bubeck, C. Imaging of the lateral structure of Langmuir-Blodgett films by metal decoration and polarization microscopy. Thin Solid Films 210/211, 674–677 (1992).

    Article  ADS  Google Scholar 

  6. Maruyama, T., Fuller, G., Frank, C. & Robertson, C. Flow-induced molecular orientation of a Langmuir film. Science 274, 233–235 (1996).

    Article  ADS  CAS  Google Scholar 

  7. Maruyama, T., Lauger, J., Fuller, G. G., Frank, C. W. & Robertson, C. R. Orientation in a fatty acid monolayer: effect of flow type. Langmuir 14, 1836–1845 (1998).

    Article  CAS  Google Scholar 

  8. Ignés-Mullol, J. & Schwartz, D. K. Alignment of hexatic Langmuir monolayers under shear. Phys. Rev. Lett. 85, 1476–1479 (2000).

    Article  ADS  Google Scholar 

  9. Ikegami, K., Mingotaud, C. & Delhaes, P. Monolayer flow and in-plane orientation induced by a rotating disk in Langmuir and Langmuir-Blodgett films of a merocyanine dye. Phys. Rev. E 56, 1987–1997 (1997).

    Article  ADS  CAS  Google Scholar 

  10. Ikegami, K., Mingotaud, C. & Delhaes, P. In-plane orientation of mesoscopic domains in Langmuir and Langmuir-Blodgett films induced by rotating disks. Thin Solid Films 329, 24–27 (1998).

    Article  ADS  Google Scholar 

  11. Edwards, D. A., Brenner, H. & Wasan, D. T. Interfacial Transport Processes and Rheology (Butterworth-Heinemann, Boston, 1991).

    Google Scholar 

  12. Kaganer, V. M., Möhwald, H. & Dutta, P. Structure and phase transitions in Langmuir monolayers. Rev. Mod. Phys. 71, 779–819 (1999).

    Article  ADS  CAS  Google Scholar 

  13. Friedenberg, M. C., Fuller, G. G., Frank, C. W. & Robertson, C. R. Direct visualization of flow-induced anisotropy in a fatty acid monolayer. Langmuir 12, 1594–1599 (1996).

    Article  CAS  Google Scholar 

  14. Cuvillier, N., Mingotaud, C. & Ikegami, K. Shear-induced optical anisotropy in a Langmuir monolayer: A Brewster angle reflectivity study. J. Chem. Phys. 111, 6982–6990 (1999).

    Article  ADS  CAS  Google Scholar 

  15. Ghaskadvi, R. S., Bohanon, T. M., Dutta, P. & Ketterson, J. B. Shear response of Langmuir monolayers of heneicosanoic (C-21) acid studied using a torsion pendulum. Phys. Rev. E 54, 1770–1773 (1996).

    Article  ADS  CAS  Google Scholar 

  16. Ghaskadvi, R. S., Ketterson, J. B. & Dutta, P. Nonlinear shear response and anomalous pressure dependence of viscosity in a Langmuir monolayer. Langmuir 13, 5137–5140 (1997).

    Article  CAS  Google Scholar 

  17. Ghaskadvi, R. S., Carr, S. & Dennin, M. Effect of subphase Ca++ ions on the viscoelastic properties of Langmuir monolayers. J. Chem. Phys. 111, 3675–3678 (1999).

    Article  ADS  CAS  Google Scholar 

  18. Kurnaz, M. L. & Schwartz, D. K. Channel flow in a Langmuir monolayer: unusual velocity profiles in a liquid-crystalline mesophase. Phys. Rev. E 56, 3378–3384 (1997).

    Article  ADS  CAS  Google Scholar 

  19. Ivanova, A., Kurnaz, M. L. & Schwartz, D. K. Temperature and flow rate dependence of the velocity profile during channel flow of a Langmuir monolayer. Langmuir 15, 4622–4624 (1999).

    Article  CAS  Google Scholar 

  20. Ivanova, A. & Schwartz, D. K. Transient behavior of the velocity profile in channel flow of a Langmuir monolayer. Langmuir 16, 9433–9438 (2000).

    Article  CAS  Google Scholar 

  21. Maffettone, P. L., Grosso, M., Friedenberg, M. C. & Fuller, G. G. Extensional flow of a two-dimensional polymer liquid crystal. Macromolecules 29, 8473–8478 (1996).

    Article  ADS  CAS  Google Scholar 

  22. Maruyama, T., Fuller, G. G., Grosso, M. & Maffettone, P. L. The dynamics of two dimensional polymer nematics. J. Non-Newtonian Fluid Mech. 76, 233–247 (1998).

    Article  CAS  Google Scholar 

  23. Jeffery, G. B. Motion of ellipsoidal particles immersed in a viscous fluid. Proc. R. Soc. Lond. A 102, 161–179 (1922).

    Article  ADS  Google Scholar 

  24. Nelson, D. R. & Halperin, B. I. Solid and fluid phases in smectic layers with tilted molecules. Phys. Rev. B 21, 5312–5328 (1980).

    Article  ADS  CAS  Google Scholar 

  25. Selinger, J. V., Wang, Z.-G., Bruinsma, R. F. & Knobler, C. M. Chiral symmetry breaking in Langmuir monolayers and smectic films. Phys. Rev. Lett. 70, 1139–1142 (1993).

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by the National Science Foundation, the donors of the Petroleum Research Fund, and the Camille & Henry Dreyfus Foundation.

Author information

Author notes

  1. Jordi Ignés-Mullol

    Present address: Department de Química Física, Universitat de Barcelona, Martí i Franquès I, Barcelona, E08028, Spain

  2. Daniel K. Schwartz

    Present address: Department of Chemical Engineering, University of Colorado, Boulder, Colorado, 80309, USA

Authors and Affiliations

    Authors
    1. Jordi Ignés-Mullol
      View author publications

      You can also search for this author in PubMed Google Scholar

    2. Daniel K. Schwartz
      View author publications

      You can also search for this author in PubMed Google Scholar

    Additional information

    Department of Chemistry, Tulane University, New Orleans, Louisiana 70118,USA

    Rights and permissions

    Reprints and permissions

    About this article

    Cite this article

    Ignés-Mullol, J., Schwartz, D. Shear-induced molecular precession in a hexatic Langmuir monolayer. Nature 410, 348–351 (2001). https://doi.org/10.1038/35066539

    Download citation

    • Received:

    • Accepted:

    • Issue Date:

    • DOI: https://doi.org/10.1038/35066539

    This article is cited by

    Comments

    By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

    Search

    Advanced search

    Quick links

    Nature Briefing

    Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

    Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing