Skip to main content
SpringerLink
Log in

Molecular orientation of a commercial thermotropic liquid crystalline polymer in simple shear and complex flow

  • Original Contribution
  • Published:
Rheologica Acta Aims and scope Submit manuscript

Abstract

In-situ X-ray scattering methods have been used to measure the average degree of molecular orientation in the commercial thermotropic copolyesteramide, Vectra B. Experiments were conducted in both homogeneous shear flow and in extrusion-fed channel flows that provided mixed shear/extensional deformations. In the channel flows, extension has a dramatic effect on the average orientation state in the vicinity of stagnation points or expansions/contractions in cross-sectional area. Of particular note, a temporary increase and subsequent decay in orientation observed in a 4:1 slit-contraction flow provides additional indirect evidence supporting the hypothesis that Vectra B exhibits director tumbling. This is consistent with results from other fully aromatic copolyesters but contrasts with findings in “model” thermotropes incorporating flexible spacers. Thus, it seems that the stiffer backbone of commercial main chain LCPs is the main feature which, apparently, leads to tumbling. Measurements of average molecular orientation in transient shear flows show some connections with the corresponding mechanical response, but fail to show the distinctive characteristics that have previously been associated with either tumbling or aligning in LCPs using similar procedures. These experiments might be adversely affected by the comparatively slow rate of data acquisition, which leads to lengthy experiments in which the sample is more prone to degradation.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9

Similar content being viewed by others

References

  1. Bedford BD, Burghardt WR (1996) Molecular orientation of a liquid-crystalline polymer solution in mixed shear-extensional flows. J Rheol 40:235–257

    Article  CAS  Google Scholar 

  2. Beekmans F, Gotsis AD, Norder B (1996) Transient and steady-state rheological behavior of the thermotropic liquid crystalline polymer Vectra B950. J Rheol 40:947–966

    Article  CAS  Google Scholar 

  3. Beekmans F, Gotsis AD, Norder B (1997) Influence of the flow history on stress growth and structure changes in the thermotropic liquid crystalline polymer Vectra B950. Rheol Acta 36:82–95

    Article  CAS  Google Scholar 

  4. Burghardt WR (1998) Molecular orientation and rheology in sheared lyotropic liquid crystalline polymers. Macromol Chem Phys 199:471–488

    CAS  Google Scholar 

  5. Caputo FE, Burghardt WR (2001) Real-time 1–2 plane SAXS measurements of molecular orientation in liquid crystalline polymers. Macromolecules 34:6684–6694

    Article  CAS  Google Scholar 

  6. Caputo FE, Burghardt WR, Berret J-F (1999) Tumbling dynamics in a nematic surfactant solution in transient shear flows. J Rheol 43:765–779

    Article  CAS  Google Scholar 

  7. Caputo FE, Ugaz VM, Burghardt WR, Berret J-F (2002) Transient 1–2 plane SAXS measurements of micellar orientation in aligning and tumbling nematic surfactant solutions. J Rheol 46:927–946

    Article  CAS  Google Scholar 

  8. Chang S, Han CD (1997) A thermotropic main-chain random copolyester containing flexible spacers of differing lengths. 2. Rheological behavior. Macromolecules 30:1656–1669

    Article  CAS  Google Scholar 

  9. Cinader DK, Burghardt WR (1999a) X-ray scattering studies of orientation in channel flows of a lyotropic liquid crystalline polymer. Polymer 40:4169–4180

    Article  CAS  Google Scholar 

  10. Cinader DK, Burghardt WR (1999b) X-ray scattering studies of orientation in channel flows of a thermotropic liquid-crystalline polymer. J Polym Sci B Polym Phys 37:3411–3438

    Article  CAS  Google Scholar 

  11. Cinader DK, Burghardt WR (2000) Molecular orientation in channel flows of main-chain thermotropic liquid crystalline polymers. Rheol Acta 39:247–258

    Article  CAS  Google Scholar 

  12. Dadmun MD, Clingman S, Ober CK, Nakatani AI (1998) Flow-induced structure in a thermotropic liquid crystalline polymer as studied by SANS. J Polym Sci B Polym Phys 36:3017–3023

    Article  CAS  Google Scholar 

  13. Donald AM, Windle AH (1992) Liquid crystalline polymers. Cambridge University Press, Cambridge

    Google Scholar 

  14. Ericksen JL (1960) Anisotropic fluids. Arch Rat mech Anal 4:231–237

    Google Scholar 

  15. Gervat L, Mackley MR, Nicholson TM, Windle AH (1995) The effect of shear on thermotropic liquid-crystalline polymers. Philos Trans Roy Soc A 350:1–27

    Google Scholar 

  16. Gillmor JR, Colby RH, Hall E, Ober CK (1994) Viscoelastic properties of a model main-chain liquid crystalline polymer. J Rheol 38:1623–1638

    Article  CAS  Google Scholar 

  17. Han CD, Chang S, Kim SS (1994) Rheological behavior of thermotropic liquid-crystalline polymers—effect of thermal and deformation histories. Mol Cryst Liq Cryst 254:335–368

    CAS  Google Scholar 

  18. Han CD, Ugaz VM, Burghardt WR (2001) Shear stress overshoots in flow inception of semiflexible thermotropic liquid crystalline polymers: experimental test of a parameter-free model prediction. Macromolecules 34:3642–3645

    Article  CAS  Google Scholar 

  19. Hongladarom K, Burghardt WR (1993) Molecular alignment of polymer liquid crystals in shear flow. 2. Transient flow behavior in poly(benzyl glutamate) solutions. Macromolecules 26:785–794

    CAS  Google Scholar 

  20. Hongladarom K, Secakusuma V, Burghardt WR (1994) Relation between molecular orientation and rheology in lyotropic hydroxypropylcellulose solutions. J Rheol 38:1505–1523

    Article  CAS  Google Scholar 

  21. Huang CM, Magda JJ, Larson RG (1999) The effect of temperature and concentration on N1 and tumbling in a liquid crystal polymer. J Rheol 43:31–50

    Article  CAS  Google Scholar 

  22. Kim SS, Han CD (1993) Transient rheological behavior of a thermotropic liquid-crystalline polymer. 1. The startup of shear flow. J Rheol 37:847–866

    Article  CAS  Google Scholar 

  23. Kim DO, Han CD, Mather PT (2000) Optical and mechanical rheometry of semiflexible main-chain thermotropic liquid-crystalline polymers with varying pendant groups. Macromolecules 33:7922–7930

    Article  CAS  Google Scholar 

  24. Larson RG (1998) The structure and rheology of complex fluids. Oxford University Press, New York, pp 10–11

    Google Scholar 

  25. Leslie FM (1979) Theory of flow phenomena in liquid crystals. Adv Liq Cryst 4:1–81

    Google Scholar 

  26. Lin HG, Winter HH (1991) High-temperature recrystallization and rheology of a thermotropic liquid-crystalline polymer. Macromolecules 24:2877–2882

    CAS  Google Scholar 

  27. Long D, Morse DC (2000) Linear viscoelasticity and director dynamics of nematic liquid crystalline polymer melts. Europhys Lett 49:255–261

    Article  CAS  Google Scholar 

  28. Maffettone PL, Marrucci G (1992) The nematic dumbbell model. J Rheol 36:1547–1561

    Article  CAS  Google Scholar 

  29. Mather PT, Jeon HG, Han CD, Chang S (2000) Morphological and rheological responses to shear startup and flow reversal of thermotropic liquid-crystalline polymers. Macromolecules 33:7594–7608

    Article  CAS  Google Scholar 

  30. Mewis J, Moldenaers P (1987) Transient rheological behavior of a lyotropic polymeric liquid-crystal. Mol Cryst Liq Cryst 153:291–300

    CAS  Google Scholar 

  31. Moldenaers P, Mewis J (1990) Relaxational phenomena and anisotropy in lyotropic polymeric liquid crystals. J Non Newt Fluid Mech 34:359–374

    Article  CAS  Google Scholar 

  32. Rendon S, Burghardt WR, New A, Bubeck RA (2004) Effect of complex kinematics on the molecular orientation distribution in injection molding of liquid crystalline copolyesters. Polymer 45:5341–5352

    Article  CAS  Google Scholar 

  33. Romo-Uribe A, Windle AH (1996) “Log-rolling” alignment in main-chain thermotropic liquid crystalline polymer melts under shear: An in-situ WAXS study. Macromolecules 29:6246–6255

    Article  CAS  Google Scholar 

  34. Romo-Uribe A, Windle AH (1999) A rheo-optical and dynamic X-ray-scattering study of flow-induced textures in main-chain thermotropic liquid crystalline polymers. The influence of molecular weight. Proc Roy Soc Lond A Mat 455:1175–1201

    CAS  Google Scholar 

  35. Semenov AN (1987) Rheological properties of a nematic solution of semiflexible macromolecules. Sov Phys JETP 66:712–716

    Google Scholar 

  36. Srinivasarao M, Garay RO, Winter HH, Stein RS (1992) Rheo-optical properties of a thermotrip liquid-crystalline polymer. Mol Cryst Liq Cryst 223:29–39

    CAS  Google Scholar 

  37. Ugaz VM, Burghardt WR (1998) In situ x-ray scattering study of a model thermotropic copolyester under shear: evidence and consequences of flow-aligning behavior. Macromolecules 31:8474–8484

    Article  CAS  Google Scholar 

  38. Ugaz VM, Burghardt WR, Zhou W, Kornfield JA (2001) Transient molecular orientation and rheology in flow aligning thermotropic liquid crystalline polymers. J Rheol 45:1029–1063

    Article  CAS  Google Scholar 

  39. Vaish N, Cinader DK, Burghardt WR, Zhou W, Kornfield JA (2001) Molecular orientation in quenched channel flow of a flow aligning main chain thermotropic liquid crystalline polymer. Polymer 42:10147–10153

    Article  CAS  Google Scholar 

  40. Zhou W, Kornfield JA, Ugaz VM, Burghardt WR, Link DR, Clark NA (1999) Dynamics and shear orientation behavior of a main-chain thermotropic liquid crystalline polymer. Macromolecules 32:5581–5593

    Article  CAS  Google Scholar 

  41. Zhou W, Kornfield JA, Burghardt WR (2001) Shear aligning properties of a main chain thermotropic liquid crystalline polymer. Macromolecules 34:3654–3660

    Article  CAS  Google Scholar 

Download references

Acknowledgments

This work was funded by the Air Force Office of Scientific Research MURI on liquid crystals (Grant F49620-97) and by NSF grant DMI-0099542. We gratefully thank A.D. Gotsis for providing the Vectra B polymer. Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) Synchrotron Research Center located at Sector 5 of the Advanced Photon Source. DND-CAT is supported by E.I. DuPont de Nemours & Co., the Dow Chemical Company, the National Science Foundation through Grant DMR-9304725, and the State of Illinois through Department of Commerce and Board of Higher Education Grant IBHE HECA NWU 96. Use of the Advanced Photon Source was supported by the US Department of Energy, Basic Energy Sciences, Office of Energy Research, under Contract No. W-31-102-Eng-38.

Author information

Authors and Affiliations

  1. Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA

    Wesley R. Burghardt & Eric F. Brown

  2. Department of Chemical Engineering, California Institute of Technology, Pasadena, CA, 91135, USA

    Maria Lujan Auad & Julia A. Kornfield

Authors
  1. Wesley R. Burghardt
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Eric F. Brown
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Maria Lujan Auad
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Julia A. Kornfield
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Burghardt, W.R., Brown, E.F., Auad, M.L. et al. Molecular orientation of a commercial thermotropic liquid crystalline polymer in simple shear and complex flow. Rheol Acta 44, 446–456 (2005). https://doi.org/10.1007/s00397-004-0424-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00397-004-0424-1

Keywords

Search

Navigation