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 composedof smectic CA glass

Elongation deformation of the smectic layer structure was examined by mecha nical 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 solidif ied with the mesogenic groups arranged in a zigzag fashion and with the lay ers aligned perpendicular to the fiber axis. The fiber could be elongated a t room temperature until the strain of around 20%. On elongation, the polym er chain was stretched and succeedingly relaxed to recover the initial zigz ag conformation. The relaxation was followed by the characteristic undulati on of smectic layers.