The orientation of liquid crystals by temperature gradients
It was reported by Stewart (1) that when the liquid crystal p-azoxyanisole was placed in a vertical temperature gradient the molecular orientation adopted was vertical when the higher temperature was at the bottom and horizontal when the higher temperature was at the top. These observations were confirmed by Holland and Stewart (2), Stewart, Holland, and Reynolds (3), and Stewart (4), the latter stressing that the horizontal orientation was not produced by convection currents; in fact the horizontal orientation was observed only when the vertical convection currents were reduced as much as possible. More recently, Picot and Fredrickson (5) und Fisher and Fredrickson (6) have doubted that a temperature gradient can exert an orienting influence, while Patharkor, Rajan, and Picot (7) give experimental evidence suggesting that such an influence may exist.
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