Thermotropic Liquid Crystals of Main-Chain Polyesters Having a Mesogenic 4,4‘-Biphenyldicarboxylate Unit. 13. Characteristic Deformation of Smectic Layer Structure Induced by Elongation of Uniaxially Oriented Fiber Composed of Smectic CA Glass

Elongation deformation of the smectic layer structure was examined by mechanical and X-ray measurements for the oriented fiber of the main-chain BB-5 polyester. In this oriented fiber, a smectic CA (SmCA) structure is solidified with the mesogenic groups arranged in a zigzag fashion and with the layers aligned perpendicular to the fiber axis. The fiber could be elongated at room temperature until the strain of around 20%. On elongation, the polymer chain was stretched and succeedingly relaxed to recover the initial zigzag conformation. The relaxation was followed by the characteristic undulation of smectic layers.