Poly(isobutylene oxide) Crystals Grown by the Evaporation of Its Hot Dilute Solution

Abstract

Hexagonal and circular crystals have been obtained by the evaporation of the hot o-dichlorobenzene solution containing a small amount of poly (isobutylene oxide).
It was confirmed that hexagonal crystals are single crystal consisting of chain folded lamellae and that a central hole within the crystals is formed at an early stage of the growth, which is created by a screw dislocation mechanism as suggested by Frank. The circular crystals consist of chain folded lamellae, however, they differ from the hexagonal crystal both in not having a central hole and having the structure with a radially oriented lamellar texture, which is similar to a two dimensional spherulite, usually known.
Hexagonal fences and concentric rings grown around the central crystals consist of radially oriented narrow lamellae under the influence of the central crystals, having hexagonal or circular shape, and it was found that these growth pattern show a periodic difference in thickness depending on the distance from the centre.
The circular crystals and the rings show negative birefringence toward radial directions, and it has been recognized very weak bright and dark concentric rings superimposed on the extinction pattern with a Maltese Cross. It was concluded that the pattern could be explained in terms of a half twist model of the lamellar crystals to the radial directions.