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Shear mechanical anisotropy of side chain liquid-crystal elastomers: Influence of sample preparation

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Abstract.

We study the mechanical anisotropy of a series of uniaxial side chain nematic elastomers prepared with the same chemical composition but with different preparation protocols. For all the compounds, the experiments performed as a function of temperature show no discontinuity in both G' // and G' ⊥ (the labels // and ⊥ stand for the director parallel, respectively perpendicular to the shear displacement) around the nematic-isotropic (N-I) phase transition temperature determined by DSC. They also all show a small decrease in G' // starting at temperatures well above this temperature (from ∼ 4° C to ∼ 20° C depending on the compound studied) and leading to a small hydrodynamic value of the G' ⊥/G' // ratio. The measurements taken as a function of frequency show that the second plateau in G' // and the associated dip in G //” expected from dynamic semi-soft elasticity are not observed. These results can be described by the de Gennes model, which predicts small elastic anisotropy in the hydrodynamic and linear regimes. They correspond to the behavior expected for compounds beyond the mechanical critical point, which is consistent with the NMR and specific heat measurements taken on similar compounds. We also show that a reduction in the cross-linking density does not change the non-soft character of the mechanical response. From the measurements taken as a function of frequency at several temperatures we deduce that the time-temperature superposition method does not apply. From these measurements, we also determine the temperature dependence of the longest relaxation time τE of the network for the situations where the director is either parallel or perpendicular to the shear velocity. Finally, we discuss the influence on the measurements of the mechanical constraint associated with the fact that the samples cannot change their shape around the pseudo phase transition, because of their strong adherence on the sample-bearing glass slides.

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References

  1. For a recent review article see H.R. Brand, H. Pleiner, P. Martinoty, Soft Matter 2, 182 (2006).

    Article  ADS  Google Scholar 

  2. P.G. de Gennes, M. Hébert, R. Kant, Macromol. Symp. 113, 39 (1997).

    Google Scholar 

  3. P.G. de Gennes, in Liquid Crystals of One- and Two-Dimensional Order, edited by W. Helfrich, G. Heppke (Springer, Berlin, 1980) p. 231.

  4. L. Golubovic, T.C. Lubensky, Phys. Rev. Lett. 63, 1082 (1989).

    Article  ADS  Google Scholar 

  5. P. Olmsted, J. Phys. II 4, 2215 (1994).

    Article  Google Scholar 

  6. M. Warner, P. Bladon, E.M. Terentjev, J. Phys. II 4, 91 (1994).

    Article  Google Scholar 

  7. M. Warner, E.M. Terentjev, Liquid Crystal Elastomers (Oxford University Press, Oxford, 2003).

  8. T.C. Lubensky, R. Mukhopadhyay, L. Radzihovsky, X. Xing, Phys. Rev. E 66, 011702 (2002)

    Article  MathSciNet  ADS  Google Scholar 

  9. The superscript $\sim$ indicates that the elastic modulus $C_{44}$ has been renormalized by director fluctuations.

  10. E.M. Terentjev, M. Warner, Eur. Phys. J. E 4, 343 (2001).

    Article  Google Scholar 

  11. S.M. Clarke, A.R. Tajbakhsh, E.M. Terentjev, M. Warner, Phys. Rev. Lett. 86, 4044 (2001).

    Article  ADS  Google Scholar 

  12. P. Martinoty, P. Stein, H. Finkelmann, H. Pleiner, H.R. Brand, Eur. Phys. J. E 14, 311 (2004).

    Google Scholar 

  13. S.M. Clarke, A. Hotta, A.R. Tajbakhsh, E.M. Terentjev, Phys. Rev. E 65, 021804 (2002).

    Article  ADS  Google Scholar 

  14. A. Hotta, E.M. Terentjev, Eur. Phys. J. E 10, 291 (2003).

    Article  Google Scholar 

  15. E.M. Terentjev, A. Hotta, S.M. Clarke, M. Warner, Phil. Trans. R. Soc. London, Ser. A 361, 653 (2003).

    MathSciNet  Google Scholar 

  16. E.M. Terentjev, M. Warner, Eur. Phys. J. E 14, 323 (2004).

    Article  Google Scholar 

  17. P. Martinoty, P. Stein, H. Finkelmann, H. Pleiner, H.R. Brand, Eur. Phys. J. E 14, 329 (2004).

    Article  Google Scholar 

  18. O. Stenull, T.C. Lubensky, Eur. Phys. J. E 14, 333 (2004).

    Article  Google Scholar 

  19. P. Martinoty, P. Stein, H. Finkelmann, H. Pleiner, H.R. Brand, Eur. Phys. J. E 14, 339 (2004).

    Google Scholar 

  20. A. Lebar, Z. Kutnjak, S. Zumer, H. Finkelmann, A. Sanchez-Ferrer, B. Zalar, Phys. Rev. Lett. 94, 197801 (2005).

    Article  ADS  Google Scholar 

  21. J. Küpfer, H. Finkelmann, Makromol. Chem. Rapid Commun. 12, 717 (1991).

    Article  Google Scholar 

  22. P. Stein, N. Aßfalg, H. Finkelmann, P. Martinoty, Eur. Phys. J. E 4, 255 (2001).

    Article  Google Scholar 

  23. J.-L. Gallani, L. Hilliou, P. Martinoty, F. Doublet, M. Mauzac, J. Phys. II 6, 443 (1996).

    Article  Google Scholar 

  24. J. Weilepp, P. Stein, N. Aßfalg, H. Finkelmann, P. Martinoty, H.R. Brand, Eur. Phys. Lett. 47, 508 (1999).

    Article  ADS  Google Scholar 

  25. J. Weilepp, J.J. Zanna, N. Aßfalg, P. Stein, L. Hilliou, M. Mauzac, H. Finkelmann, H.R. Brand, P. Martinoty, Macromolecules 32, 4566 (1999).

    Article  ADS  Google Scholar 

  26. J.J. Zanna, P. Stein, J.D. Marty, M. Mauzac, P. Martinoty, Macromolecules 35, 5459 (2003).

    Article  ADS  Google Scholar 

  27. P. Martinoty, L. Hilliou, M. Mauzac, L. Benguigui, D. Collin, Macromolecules 32, 1746 (1999).

    Article  ADS  Google Scholar 

  28. D. Collin, P. Martinoty, Physica A 320, 235 (2003).

    Article  ADS  Google Scholar 

  29. O. Stenull, T.C. Lubensky, Phys. Rev. E 69, 051801 (2004).

    Article  MathSciNet  ADS  Google Scholar 

  30. P.G. de Gennes, C. R. Acad. Sci. Sér. B 281, 101 (1975).

    Google Scholar 

  31. S. Disch, C. Schmidt, H. Finkelmann, Macromol. Rapid Commun. 15, 303 (1994).

    Article  Google Scholar 

  32. W. Kaufhold, H. Finkelmann, H.R. Brand, Makromol. Chem. 192, 2555 (1991).

    Article  Google Scholar 

  33. J. Küpfer, H. Finkelmann, Macromol. Chem. Phys. 195, 1353 (1994).

    Article  Google Scholar 

  34. J. Schätzle, W. Kaufhold, H. Finkelmann, Makromol. Chem. 190, 3269 (1989).

    Article  Google Scholar 

  35. M. Warner, J. Mech. Phys. Solids 47, 1355 (1999).

    Article  MATH  MathSciNet  ADS  Google Scholar 

  36. G. Verney, M. Warner, Macromolecules 28, 4303 (1995).

    Article  ADS  Google Scholar 

  37. M. Schönstein, W. Stille, G. Strobl, Eur. Phys. J. E 5, 511 (2001).

    Article  Google Scholar 

  38. There was a confusion in reference 12. The samples were not preheated at $T = 120$^C, and placed into the cell also heated at $T = 120$^C, as written in the Section Experimental set-up, lines 21--24, column 2. In fact, the samples were placed into the cell at room temperature. Then, the cell was heated up to 120^C and the measurements taken by decreasing the temperature.

  39. The deviations from the Rouse behavior observed for the parallel and perpendicular geometries are not due to the mechanical constraint associated with the fact that the shape change of the sample cannot occur in the cell, because they are observed by placing a new sample into the cell at each temperature of measurement.

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Authors and Affiliations

  1. Institut de Mécanique des Fluides et des Solides, UMR 7507, CNRS-ULP, 67000, Strasbourg, France

    D. Rogez, G. Francius & P. Martinoty

  2. Institut für Makromolekulare Chemie, Stefan-Meier-Str. 31, 79104, Freiburg, Germany

    H. Finkelmann

Authors
  1. D. Rogez
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  2. G. Francius
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  3. H. Finkelmann
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  4. P. Martinoty
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Correspondence to P. Martinoty.

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Rogez, D., Francius, G., Finkelmann, H. et al. Shear mechanical anisotropy of side chain liquid-crystal elastomers: Influence of sample preparation. Eur. Phys. J. E 20, 369–378 (2006). https://doi.org/10.1140/epje/i2005-10132-5

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  • DOI: https://doi.org/10.1140/epje/i2005-10132-5

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