As reported elsewhere (Cai and Zhang, 2005, Cai and Zhang, 2006 and Cai et al., 2007), an aqueous solution of 7 wt% NaOH/12 wt% urea was precooled to −12 °C in a refrigerator for 20 min, to which a known weight of native cellulose (NC) was dispersed with vigorous agitation for 5 min. The transparent cellulose solution was centrifuged at 4000 rpm for 10 min to remove the insoluble residuals and air bubbles. RC film was then prepared using a template method. Briefly, a mould was made using a tape frame stuck to a sheet of glass plate. The cellulose solution was then cast in the mould and immediately dipped into the coagulant for 5 min to obtain wet RC films. The chemicals remaining in the film were removed by thorough rinsing with deionised water. Finally, the film was dried at a constant temperature (30 °C) and humidity (65%) for 24 h.