Extensional Flow of a Two-Dimensional Polymer Liquid Crystal

Abstract

The transient behavior of a polymeric nematic liquid crystal interface in extensional flows is studied both experimentally and theoretically. Monolayers of the hairy rod polymer phthalocyaninatopolysiloxane subjected to two-dimensional, transient, extensional flows are modeled with the two-dimensional analogue of the rigid rod model. The scalar order parameter and the director orientation are compared with the experimental observables. Two parameters appear in the model: an average rotational diffusivity and the intensity of the nematic field. The average rotational diffusivity is determined by fitting relaxation experiments. The intensity of the nematic field, which is modeled with the Onsager potential, is determined by starting from the molecular parameters. A good quantitative agreement is obtained between experiments and theoretical predictions.

Monodomain response of arbitrary aspect ratio nematic polymers in general linear planar flows

“…In this paper, we call Eq. (19) the canonical flow, because after a rotation of coordinates (x, y), any general planar linear flow can be transformed into this two-parameter family in the rotated coordinates (see below). • Horizontal shear.…”

Phase Diagram of Nematic Polymer Monolayers with the Onsager Interaction Potential

“…The first nematic branch intersects with the isotropic branch at b = 3/2 , the second nematic branch at b = 15/2 , the third nematic branch at b = 35/2 . In general, if 2 = 4 = · · · = 2 j−1 = 0 but 2j = 0, then in (29) for k = j we must have…”

“…Rigid, rodlike liquid crystalline polymers have been of considerable interest in thin films because of their stability, nonlinear optical properties, and role as alignment layers for liquid crystal displays. 29 Experiments have shown that the dynamic behavior of monolayer nematic polymers can be quantitatively captured by the simple molecular model of Doi and Hess for both extensional and simple shear flows. 29 32 Numerical and theoretical studies on the two-dimensional liquid crystal polymers have also been conducted by many researchers.…”

Thermodynamic Model of Structure and Shape in Rigid Polymer‐Laden Membranes

“…The characterization of nematic order is given by the 2 Â 2 symmetric traceless quadrupolar tensor order parameter Q: [15,16,21,22] …”

“…The surface fluid model balance equations include the membrane force balance and the membrane torque balance. [1,[22][23][24][25] The presentation of the basic background material in this section is from Ref. [1,[23][24][25] Membrane Stresses and Membrane Force Balance Equation…”