Morphological Study of hydroxypropyl cellulose films prepared from thermotropic melt under shear

Abstract

A strain-induced crystallization behavior of hydroxypropyl cellulose (HPC) from the thermotropic liquid-crystalline state is described based on morphological observations by electron microscopy. It is shown that originally round-shaped particles behave as a structure unit in formation of a variety of supermolecular architectures of HPC films prepared from the thermotropic melt under shear. In an oriented HPC film obtained under weak shear, many round particles are elongated and aligned in the direction of shear (SD), but with their bodies bent to some degree. As deformation increases further, fibrillation occurs on the surface of the elongated particles, and then the resulting fibrils are arranged in a zigzag fashion along the SD to form a banded structure. In some cases, a pleated arrangement of fibrils is noticeable between bands. The structural transformation mechanism of thermotropic HPC under shear is discussed in detail on the basis of the morphological evidence.