Ultra-slow director rotation in nematic side-group polymers detected by N.M.R.

Putten, D. van der; Schwenk, Norbert; Spiess, Hans Wolfgang

doi:10.1080/02678298908029187

Cited by 17 publications

(2 citation statements)

References 14 publications

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“…Although the accuracy in the determination of yj is normally higher than for the shear viscosity q2, this advantage is annihilated by the large contribution of the non-divergent part yp. The experimental values for v [71,77,78] are comparable with the theoretical value of 0.33 [79].…”

Section: Divergence At a Phase Transition To A Smectic A Phasesupporting

confidence: 79%

Nematic Liquid Crystals: Physical Properties, Section 2.5

Kneppe¹,

Schneider²,

Demus³

et al. 1998

Handbook of Liquid Crystals

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Section: Divergence At a Phase Transition To A Smectic A Phasesupporting

confidence: 79%

Nematic Liquid Crystals: Physical Properties, Section 2.5

Kneppe¹,

Schneider²,

Demus³

et al. 1998

Handbook of Liquid Crystals

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“…The orientational relaxation of LC polymers has experimentally been studied in [19,30] and a substantial growth in the relaxation time of the director of nematic comb-shaped polymers as compared to low-molecular-weight systems has been found.…”

Section: Dn I Dtmentioning

confidence: 99%

Relaxation thermodynamics and viscoelasticity of anisotropic polymer systems

Volkov

2005

J Eng Phys Thermophys

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A theory of asymmetric viscoelasticity of anisotropic polymer systems has been formulated based on the relaxation dynamics of irreversible processes. Consideration has been given to the effect associated with the relaxation of couple stresses.Introduction. Much attention has been given recently to studying the viscoelasticity of different anisotropic polymer systems. This is primarily true of polymer liquid crystals (LCs), cross-linked LC elastomers, polymer nanocomposites, and polymer suspensions. Their most significant difference from traditional polymer materials is the presence of relaxation anisotropy. The viscoelastic characteristics of anisotropic polymer media are tensor quantities. Therefore, unlike isotropic systems, they are determined by a substantially larger number of basic macroscopic parameters. Experimental determination of the tensor rheological properties of anisotropic polymer systems represents the most complicated problem. This field of rheology, on the whole, is only in the initial stage of development.There can be two theoretical approaches to the rheology of anisotropic polymer systems. The first approach is based on molecular dynamics. It enables one to study the physical nature of anisotropic viscoelastic effects. The second, phenomenological, approach is restricted to studying only the macroscopic properties of these fairly complex polymer media. One is able, within the framework of this approach, to allow for the influence of the motion and strain of the microstructure of a medium on its rheological properties by introducing structural variables. The prime objective of continuum theories is the establishment of general constitutive equations under the minimum assumptions of the molecular structure of anisotropic media. Molecular theories are based on quite specific assumptions of the structure of these media and operate, unlike continuum theories, with a few molecular parameters.The greatest progress toward description of the dynamics of low-molecular-weight LCs has been made at present using continuum theories [1][2][3][4][5]. An analogous situation is also observed in the theory of viscoelasticity of polymer LCs. The continuum theory of anisotropic viscoelasticity of LC polymers has been initiated by the investigations in [6][7][8][9][10][11]. A quasilinear rheological equation of state with anisotropic relaxation time and viscosity was formulated in them for simple reasons of symmetry. In this approach, an important role is played by the molecular flexibility of LC polymers and its associated elastic strains accompanying their flow. The anisotropic nonlinear viscoelasticity of polymer systems with different degrees of rigidity has begun to be studied in [12][13][14][15][16] within the framework of the classical thermodynamics of irreversible processes. This approach is based on the introduction of internal (latent) variables for description of viscoelastic effects. Here, critical is the fact that the physics of such continua can be described in general form by neither mechanics nor...

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Spinning Liquid Crystalline Samples

Courtieu

2007

Encyclopedia of Magnetic Resonance

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Ultra-slow director rotation in nematic side-group polymers detected by N.M.R.

Cited by 17 publications

References 14 publications

Nematic Liquid Crystals: Physical Properties, Section 2.5

Nematic Liquid Crystals: Physical Properties, Section 2.5

Relaxation thermodynamics and viscoelasticity of anisotropic polymer systems

Spinning Liquid Crystalline Samples

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