Changes of structure and property of alkali soluble hydroxyethyl celluloses (HECs) and their regenerated films with the molar substitution

Hydroxyethyl celluloses (HECs) with low molar substitutions (MS) were prepared by reaction of alkali cellulose with ethylene oxide (EO) in a heterogeneous process. NMR, FTIR, WAXD, TG, solubility and tensile tests were adopted to investigate the changes of structures and properties of HECs with their MS values. NMR results showed that the hydroxyethyl groups were introduced into the cellulose chains as expected, causing the destruction in ordered structure and a loss in crystallinity. Crystal transformation from cellulose I of raw cellulose to cellulose II of HECs was proved by different methods. The crystalline structure of HEC seriously deteriorated with the rising MS value, accompanying lower thermal stability and improvements on its solubility in 8 wt% NaOH solvent and moisture related properties such as water retention. These different properties depending on the MS values endowed HECs with various potential applications in the form of regenerated cellulose fibers or other absorbent materials.