Figure 9.
Examples of models of two bioinspired nanocomposites based on cellulose elements and polymeric matrix and characterized by different performances; both models can be considered analogous to the natural MCT model. On the left: basic structure of a hybrid hydrogel consisting of a network of mechanically isolated CNFs crosslinked with Ca2+ (green inset) and a network of PVA (polyvinyl alcohol) crosslinked by dynamic boronic bonds (red inset). The CNF/PVA hydrogel consists of a double network crosslinked by hydrogen bonds (redrawn and modified from [95]). Its main specific property is self-healing (explained below in main text) as schematically shown on the bottom left. On the right: basic structure of a shape-memory nanocomposite consisting of chemically isolated CNC whiskers (cellulose nanocrystals) immersed in PU (polyurethane) matrix (redrawn and modified from [100]). Orientation/alignment of CNC whiskers and crosslinks between them can be modulated according to wetting/drying and stretching conditions. The main property of the nanocomposite is shape-memory whose mechanism is shown on the bottom right (redrawn and modified from [91]).