Structure and morphology of polydiacetylene single crystals

Abstract

Single crystals of certain diacetylene monomers prepared by solid-state polymerization offer a unique opportunity to study the structure and properties of polymer crystals. Two distinct morphological forms of one polydiacetylene (pTS) have been examined by transmission electron microscopy. In one case crystals have been prepared in the form of lamellae which are 100% crystalline. It has been shown by electron diffraction and cleavage experiments that in these crystals the polymer molecules are in a chain-extended conformation in contrast to the normal chain-folded lamellar single crystals obtained by solution crystallization of conventional polymers. A completely different form of pTS is obtained by crystallization of partly polymerized material from dilute solution. In this case the pTS is in the form of fibrous crystals up to 1000 Å in diameter and several µm long. It has been found that the fibrous crystal have a crystal structure which is different from that of the solid-state polymerized crystals but the direction of chain orientation within the fibres is not yet known.