Electron-Microscope Study of Cotton Treated with Inter- and Intracrystalline Swelling Agents

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Abstract
Electron micrographs are presented of cotton cellulose treated with aqueous solutions of the inter- and intracrystalline swelling agents, morpholine, piperidine, piperazine, ethylenediamine, and zinc chloride. The concentration of each swelling agent was such as to produce maximum recoverable swelling of cotton cellulose. Physical and fine-structure characteristics of these treated cottons, after complete removal of the swelling agent, revealed that morpholine and piperidine are intercrystalline and piperazine, ethylenediamine, and zinc chloride are intracrystalline swelling agents. Thisw as confirmed by electron-microscope determination of microfibrillar morphology and dimensions. The layer-expansion technique was used to examine these treated cottons along with samples that had been treated with sodium hydroxide and phosphoric and sulfuric acids. The electron micrographs revealed marked gradation in swollen and decrystallized cottons, which may serve as a visual scale at the microfibrillar level for cotton decrystallized to varying degrees. To confirm the extent to which the morphology of decrystallized cotton observed by the layer-expansion technique really exists in the swollen state before the removal of the swelling agent, the cottons treated with sodium hydroxide, morpholine, zinc chloride, and sulfuric acid were embedded in glycol methacrylate in the swollen state and the ultrathin cross sections of these were examined.