Effects of crosslinking ratio and aging time on properties of physical and chemical cellulose gels via 1-butyl-3-methylimidazolium chloride solvent

Papers used in the field of electro-responsive applications are known as Electroactive-papers (EAPaps), consisting primarily of a cellulose. 1-Butyl-3-methylimidazolium chloride is an interesting ionic liquid that acts as an effective cellulose solvent for EAPaps due to its high solubility without chain derivatization, less chain degradation, and stability in electro-responsive applications. In our work, physical and chemical cellulose gels were fabricated and studied for the effects of various crosslinking ratios (CR) and aging time (t_ag), with glutaraldehyde acting as the crosslinking agent. The crosslinking reaction conversion could be increased by increasing the CR and t_ag; the reaction products were ketone linkages and by-product water molecules. A difference in optical properties could be observed and related to the differing amounts of ketone linkages, as confirmed by FTIR-ATR quantitative analysis. UV–visible spectra showed that the prepared samples had a maximum wavelength λ_max nm, a characteristic of ketone linkages. By-product water molecules exhibited plasticizing effects, as observed by the decrease in the storage moduli (G′) at 1 day aging time. The outward migration of by-product water molecules caused a slight increase in G′ at 15 days aging time due to a closer packing. The by-product water molecules induced the H⁺-hopping and more disordered domains resulting in an ease in ion migration. Our paper-gels showed potential characteristics towards electro-responsive applications: less preparation time (<14 h) and stable gel properties.