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(a) Nematic cell prepared with nonrubbed glass plates between crossed polarizers. The places where two fringes cross each other correspond to vertical disclination lines of order 1 that probably escape in the third dimension and reduce to surface point defects Ref. 2. The average distance between them is . (b) Domains of opposite twists separated by virtual disclination lines in a cell built with unidirectionally polished plates. Insert: SEM photograph of a polished plate. The bar length is .
(a) Similar sample to Fig. 1(b), but prepared with of polymer. The virtual disclination lines are located close to the substrates as observed on focusing the microscope. They delimit domains of opposite twists (see, e.g., Ref. 5). (b) Sample built with one plate from the cell of (a) and a new counterplate (see text). The previous domains and lines are memorized, as imprinted on the substrate, while new ones superpose (arrow).
Deviation angles of the nematic director relative to the rubbing direction on each interface of cells, respectively, containing pure 5CB, 5CB with monomers, and 5CB with polymers. This angle is obtained from the difference between the polarization directions of light arising from neighboring domains, divided by 4. , , and are measured before, after a “soft,” and after a “hard” incursion in the isotropic phase, respectively, (see text). Insert: Sketch depicting the gliding angle , the elastic deviation due to the torque , and the recorded angle ; , , and being, respectively, the polishing direction, the easy axis before transition to the isotropic phase, and the recorded axis.
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