Cellulose nanofibril foams: Links between ice-templating conditions, microstructures and mechanical properties

• Cellulose nanofibril (NFC) foams with various structural and mechanical properties were fabricated using cryodesiccation.
• Two solidification techniques of NFC suspensions were used: direct quenching and mechanical stirring followed by quenching.
• Solidification, type and concentration of NFC suspensions affected both foam microstructure and mechanical performances.
• 3D X-ray microtomography images of in situ compression experiment unveiled the deformation mechanisms of foam cells.

This study aimed at investigating how ice templating conditions affected the shrinkage, the microstructure, and the mechanical properties of cellulose nanofibril (NFC) foams. Enzymatic and TEMPO-oxidized NFC foams were fabricated using two solidification techniques, i.e., quenching NFC suspensions in temperature-controlled baths, and mechanical stirring of NFC suspensions during solidification followed by quenching, prior to freeze-drying. Foams prepared by direct quenching using stabilized TEMPO-oxidized NFC suspensions exhibited higher specific mechanical properties and more regular anisotropic cells with unimodal size than enzymatic NFC foams. In addition, NFC concentration and NFC morphology severely affected the foam shrinkage and