Abstract
A macroscopic continuum mechanical model for incompressible side-chain nematic polymers, under isothermal conditions is given. The model is a synthesis of a transient network model and the standard nematorheological model. Simplifications in the model yield constitutive equations that are identical to well known Theological models for polymer melts and for low molar mass nematics. A detailed analysis of four possible composite orientation modes of polymer backbone and mesogenic side groups in uniaxial extensional flow is given. It is shown that the thermal sensitivity of the viscoelastic parameters leads to thermally-induced orientation transitions. The extension rate sensitivity of the competition between elastic and flow orienting effects leads to flow-induced orientation transition. The role of smectic A fluctuations in thermally-induced transitions during uniaxial extensional nematic flow is elucidated. The model is able to predict and explain the experimentally observed orientation modes and thermally-induced orientation transitions of a side-chain nematic polymer subjected to uniaxial extensional flow.
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References
Bruinsma RF, Safinya CR (1991) Landau theory of the nematic-smectic A phase transition under shear flow. Phys Rev A43:5377–5404
Brûlet A, Boue F, Keller P, Davidson P, Strazielle C, Cotton JP (1994) SANS study of deformation and relaxation of a comb-like liquid crystal polymer in the nematic phase. J Phys II France 4:1033–1048
Chandrasekhar S (1992) Liquid crystals. Second Edition, Cambridge University Press, Cambridge
deGennes PG (1974) The physics of liquid crystals. Clarendon Press, Oxford
deGroot SR, Mazur P (1962) Non-equilibrium thermodynamics. North-Holland Publishing Company, Amsterdam
Edwards BJ, Beris AN, Grmela M (1991) The dynamical behavior of liquid crystals: a continuum description through generalized brackets. Mol Cryst Liq Cryst 201:51–86
Ericksen JL (1960) Transversely isotropic fluids. Kolloid-Zeitschrift 173:117–122
Finkleman H (1989) In: McArdle CB (ed) Side chain liquid crystal polymers. Chapman Hall, New York
Guo W, Davis FJ, Mitchell GR (1994) Side-chain liquid-crystal copolymers and elastomers with a null coupling between the polymer backbone and the mesogenic groups. Polymer 14:2932–2940
Ho ASK, Rey AD (1991) Orienting properties of discotic nematic liquid crystals in Jeffrey-Hamel flows. Rheol Acta 30:77–88
Jähnig F, Brochard F (1974) Critical elastic constants and viscosities above a nematic-smectic A transition of second order. J Physique 35:301–313
Kannan RM, Kornfield JA, Schwenk N, Boeffel C (1993) Rheology of side-group liquid-crystalline polymers: effect of isotropic-nematic transition and evidence of flow alignment. Macromolecules 26:2050
Kwon TH, Shen S-F (1984) A unified constitutive theory for polymeric liquids. 1. Basic considerations and simplified model. Rheol Acta 23:217–230
Larson RG (1988) Constitutive equations for polymer melts and solutions. Butterworths, Stoneham
Marrucci G (1991) Rheology of nematic polymers. In: Cifferi A (ed) Liquid crystallinity in polymers: principles and fundamental properties. VCH Publishers, New York pp 395–422
McMillan WL (1974) Time-dependent Landau theory for the smectic-A-nematic phase transition. Phys Rev Lett 9:1720–1724
Matice CJ, Van Arsdale WE (1990) Weakly elastic fluids. J Rheol 34:993–1010
McArdle CB (ed) (1989) Side chain liquid crystal polymers. Chapman Hall, New York
Mitchell GR, Davis FJ, Guo W (1993) Strain-induced transitions in liquid-crystal elastomers. Phys Rev Lett 71: 2947–2950
Plate NA, Shibaev VP (1987) Comb-shaped polymers and liquid crystals. Plenum Press, New York
Pleiner H, Brand HR (1992) Local rotational degrees of freedom in nematic liquid crystalline side-chain polymers. Macromolecules 25:895–901
Petrie CJS (1979) Elongational flows. Pitman, London
Rey AD, Denn MM (1988) Converging flow of tumbling nematic liquid crystals. Liquid crystals 4:253–272
Takserman-Krozer R, Ziabicki A (1963) Behaviour of polymer solutions in a velocity field with parallel gradient. I. Orientation of rigid ellipsoids in a dilute solution. J Polymer Science A1:491–506
Warner M (1989) The physical principles of side chain polymer liquid crystals. In: McArdle CB (ed) Side chain liquid crystal polymers. Chapman Hall, New York, pp 7–28
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Rey, A.D. Macroscopic theory of orientation transitions in the extensional flow of side-chain nematic polymers. Rheola Acta 34, 119–131 (1995). https://doi.org/10.1007/BF00398431
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DOI: https://doi.org/10.1007/BF00398431