Preparation and characterization of transparent cellulose nanocrystal film using freeze–thaw technique

The objective of the study was to prepare self-assembled transparent cellulose nanocrystal (CNC) films utilizing freeze–thaw technique. To date, self-assembled transparent CNC solid film can be obtained through chemical doping. Here, an easy alternative route was demonstrated to produce such film without chemical modification. It was found that the freeze–thaw method completely eliminated the chiral nematic structure, resulting in completely transparent films without structural color. Detailed internal structure characterization using SEM, XRD, and UV–Vis spectroscopy coupled with optical property analysis revealed a remarkable improvement in the clarity and sharpness of freeze–thaw based CNC films without compromising transmittance and haze, showing promise of freeze–thaw based CNC films in packaging and coating applications.