Construction of network-like cross-linked cellulose aerogel films with water-responsive properties for visualization of pH changes

Using epichlorohydrin as a cross-linking agent for cellulose and red radish pigment (R) as a pH-smart response indicator, a network-like cross-linked cellulose aerogel film (R-CEF) with water-responsive properties for visu-alizing pH changes was constructed by a simple method. In R-CEF, epichlorohydrin cross-linked cellulose aerogel film (CEF) as a smart responsive substrate provides a cross-linked structure with high porosity and good compatibility with R. XPS and FTIR structural analysis elucidate the objective fact of the existence of hydrogen bonds and intermolecular interactions between R and CEF. SEM showed that the addition of R changed the network cross-linked structure of CEF, making the original sponge structure into a layered structure after absorbing water, showing the intelligent response characteristics of R-CEF-7 in contact with water. The color change of the manufactured indicator (R-CEF-7) is evident from red to pink in acidic (pH=3 to pH=5) and from pink to yellow in alkaline (pH=10 to pH=13). Furthermore, R-CEF-7 showed good antibacterial properties and intelligent response characteristics to different pH values due to the contribution of R. This study provides new insights into the design and construction of pH-responsive and water-responsive cellulose-based smart composites.

Automated summary

By using epichlorohydrin as a cross-linking agent and red radish pigment as a pH indicator, a network-like cross-linked cellulose aerogel film (R-CEF) with water-responsive properties was successfully fabricated. The R-CEF showed high porosity and good compatibility due to the cross-linked structure of cellulose aerogel film (CEF). SEM analysis revealed that the addition of red radish pigment changed the structure of CEF, resulting in intelligent response characteristics of R-CEF-7 upon water absorption. The color change of R-CEF-7 from red to pink in acidic conditions (pH=3 to pH=5) and from pink to yellow in alkaline conditions (pH=10 to pH=13) demonstrated its pH-responsive properties.