Moisture and solvent responsive cellulose/SiO2 nanocomposite materials

Water responsive SiO 2 /cellulose nanocomposite hydrogels and films were constructed, for the first time, by dispersing SiO 2 nanoparticles into cellulose solution in LiOH/urea solvent, and then by crosslinking with epichlorohydrin or regeneration in coagulation bath, respectively. The cellulose nanocomposite materials were characterized by Field emission scanning electron microscopy, FTIR, dynamic rheology, wide angle X-ray diffraction and mechanical test. The SiO 2 /cellulose nanocomposites at wet state or in water displayed unique behaviors, showing higher light transmittance than those before contacting with water. The results revealed that strong hydrogen-bonding interaction among water, cellulose and SiO 2 led the good dispersion of SiO 2 nanoparticles in the cellulose matrix. The incorporation of SiO 2 nanoparticles improved the transmittance and mechanical strength of the cellulose hydrogels, and also enhanced the mechanical strength of the films. Especially, the cellulose/SiO 2 nanocomposite films were milky at dry state, and changed to transparent after being soaked in water, different from the cellulose film without the SiO 2 nanoparticles. In our findings, SiO 2 and cellulose with water could form strong hydrogen bonding to create a homogenous network structure. The cellulose/SiO 2 composite as a smart material exhibited moisture and solvent responsiveness, showing potential applications in moisture detection.