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A theory for flowing nematic polymers with orientational
distortion

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J. J. Feng, G. Sgalari and L. G. Leal

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*J. Rheology.* 44, 1085-1101(2000)

**Abstract** - Using a nonlocal nematic potential, we
generalize the Doi theory for nematic polymers to include distortional
elasticity. We derive an evolution equation for the configuration tensor
and a constitutive equation for a nonlocal stress tensor which is consistent
with the long-range order in nematic polymers. One of the interesting effects
of distortional elasticity is the appearance of a mean-field torque on
the molecules as they are forced away by flow from their preferred orientation.
This torque gives rise to an antisymmetric part of the stress tensor. With
a few molecular parameters, the complete system of equations is capable,
we believe, of describing the evolution of the texture and the dynamics
of disclinations in flowing nematic polymers. Thus, for the first time,
a suitable platform for exploring complex flows of nematic polymers is
established. In the limit of weak flows and small distortions, the theory
properly reduces to the Leslie-Ericksen theory. The Leslie viscosities
are derived in terms of molecular parameters.