Topochemical Mechanisms Involved in the Preparation and Deacetylation of Partially Acetylated Cottons

Iodine sorption and moisture sorption data and some density, x-ray, and infrared data have been obtained on partially acetylated (PA) cottons before and after progres sice deacetylation with 2 N hydrochloric acid or with N 2 sodium hydroxide. The re sults substantiate the accepted theory that in the partial acetylation of cotton the amor phous regions are acetylated first. They also show that deacetylation of PA cottons by these two reagents proceeds by different mechanisms. With hydrochloric acid. the acetylated amorphous cellulose is deacetylated more or less completely throughout the fiber before the, acetylated crystalline is attacked. With sodium hydroxide both are de acetylated simultaneously with little or no selectivity, so that deacetylation proceeds annu larlv from the surface of the fiber inward.

The properties of the original PA cottons differed markedly from those of the same acetyl content obtained by deacetylation. The properties depended further upon the reagent used for deacetylation and on the acetyl content before deacetylation. These differences in properties can be attributed to differences in the proportions and distribu tion of amorphous, crystalline. acetylated amorphous. and acetylated crystalline cellulose within the fiber and also to differences in the fine structure. degree of lateral order, and stress patterns resulting from the inhomogeneity of the volume changes which take place during acetylation or deacetylation.