Solid-state morphology of aromatic-aliphatic polyester crystallized from smectic liquid crystal

Abstract

The solid-state morphology of poly(hexamethylene p,p'-bi-benzoate) (BB-6) and its dependence on the texture of the smectic liquid crystal state from which it crystallized were studied using electron microscopy, polarizing optical microscopy, and small-angle x-ray diffractometry. Thin films of BB-6 suitable for the microscopy were prepared by casting a hot solution of the polymer in tetrabromoethane onto mica at 150°C. The as-cast film of BB-6 was first heated to 260°C, maintained in the smectic range (210°C), and then cooled gradually to room temperature. A number of types of defect structures—such as Dupan cyclides, edge dislocation, tilt walls, and disclinations — were observed in the solid BB-6 formed from the smectic melt. On the basis of the electron microscopy and small-angle x-ray diffractometry, it is suggested that folded-chain crystals are formed during the crystallization from the smectic melt. Electron microscopic observations of the solid BB-6 and its orientation behavior under shear can be reasonably explained by assuming the presence of a precursory chain-folded layer structure in the smectic liquid crystal of BB-6.