Gel Permeation Properties of Cellulose

Abstract

Application of gel permeation chromatography, which has been shown to be an effective means of measuring changes produced in the accessibility of decrystallized cotton cellulose by one form of formaldehyde cross-linking [9, 10], has been extended to the study of alterations of the structure of decrystallized cotton produced by intro duction of formaldehyde cross links under various other reaction conditions. These include reaction in aqueous solution (Form W), in the vapor phase (Form V), in acetic acid solution (Form D), each with high and low concentrations of formaldehyde, and in a bake-cure process (Form C). The properties determined by gel permeation chroma tography are the effective internal solvent volume derived from measurements of selective permeability to solutes of decreasing molecular weight and the limit of per meability to solutes of increasing molecular size. Striking differences were revealed in both the nature and magnitude of the alterations of accessibility resulting from differ ent reaction conditions employed for formaldehyde cross-linking. Corresponding changes were observed in gross properties of the cellulose polymer gels, such as the extent of swelling measured by the volumes occupied by the swollen gels per gram of dry solids. Accessibility was increased by reactions in aqueous solution which produced cellulose having larger internal volumes and permeability limits than the unmodified, decrystallized , cellulose. The reaction catalyzed by hydrochloric acid in the acetic acid medium formed products having larger internal volumes, but somewhat lower limits of permeability. Both the internal volume and the permeability limit were decreased by the bake-cure process which produced a polymer having much lower accessibility than the unmodified, decrystallized cellulose.