Conclusions
RC films were prepared using precooled 7 wt% NaOH/12 wt%urea as cellulose dissolving solvent and an acetone/water mixture with different volume ratios as coagulants. The dried RC films have a distinct slow-release effect on small ions, such as Na+and OH−,in aqueous solution. This is attributed to the small pore size of the film, which induces a so-called capillary effect. The degree of crystallinity is similar for all RC films at different ϕ, but the apparent crystal size varies due to the selective adsorption of NaOH on spe-cific crystal planes. The microstructure and mechanical properties of the RC films reveal an obvious dependence on ϕ. At ϕ = 2.0, a densely interwoven fibril-like structure is formed in the RC film,which is responsible for a higher strain to failure, whereas homogeneous granular morphology tends to be fabricated at higher ϕ,leading to a higher tensile strength. The results shown here are expected to provide a better understanding of both fundamental and practical applications of cellulose.