Mercerization of cellulose. IV. Mechanism of mercerization and crystallite sizes

Using the Guinier plot, the 200 reflection profile of ramie cellulose I was resolved into two components. One component represented a crystallite size of ∼ 20 Å, and the other component represented a crystallite size of ∼ 61 Å. These components were followed during the conversion of cellulose I to Na–cellulose I, in order to estimate the contribution of the smaller crystallites to the early rapid stage of conversion. From the intensity ratio of the two components, it appears that during the first ∼ 20% conversion the formation of Na–cellulose I occurs mainly in the oriented amorphous regions of the fiber. Following this, up to ∼ 65% conversion the destruction and transformation of small crystallites takes place. The small average size of the ∼ 20 Å crystallites, as well as their relatively high reactivity to alkali, appear to facilitate the conversion of the parallel‐chain cellulose I structure to an antiparallel one.