Liquid Crystal Systems from Fibrillar Polysaccharides

Abstract

THE preparation of a neutral aqueous suspension of cellulose crystallites by hydrolysis in strong sulphuric acid (952 gm./l.) at 30 or 40° C. for 24 hr. has been described¹. A similar suspension of crystallite particles of chitin was prepared by treating 20 gm. of purified chitin from crab shells for 1 hr. in 750 ml. of 2.5 N hydrochloric acid under reflux. Afterwards, the excess acid was decanted and distilled water was added. At this stage, the chitin hydrolysate was still essentially a sediment and was well on the acid side when it was given three passes through a ‘Minisonic’ homogenizer (Sonic Eng. Corp., Stamford, Conn.). From this treatment, a stable isotropic suspension was obtained and the pH had risen to 3.5. The rise in pH is probably due to release, from within the crystallites, of some unacetylated amino-groups which complexed with a proton to give $\text{N}{\text{H}}_{{\text{3}}^{\text{+}}}$ at the crystallite surfaces. The presence of free NH₂ groups in chitin, which is supposed to be a polymer of N-acetyl-d-glucosamine is not unexpected since purification procedures involve alkaline conditions which can saponify acetyl groups. Electron micrographs of the stable suspension show the presence of rod-like particles of similar dimensions to the cellulose crystallites².