The
purpose of this research is to develop strong and tough wood-based
hydrogels, which are reinforced by an aligned cellulosic wood skeleton.
The hypothesis is that improved interfacial interaction between the
wood cell wall and a polymer is of great importance for improving
the mechanical performance. To this end, a facile and green approach,
called ultraviolet (UV) grafting, was performed on the polyacrylamide
(PAM)-infiltrated wood skeleton without using initiators. An important
finding was that PAM-grafted cellulose nanofiber (CNF) architectures
formed in the obtained hydrogels under UV irradiation, where CNFs
themselves serve as both initiators and cross-linkers. Moreover, an
alkali swelling treatment was utilized to improve the accessibility
of the wood cell wall before UV irradiation and thus facilitate grafting
efficiency. The resulting alkali-treated Wood-g-PAM
hydrogels exhibited significantly higher tensile properties than those
of the Wood/PAM hydrogel and were further assembled into conductive
devices for sensor applications. We believe that this UV grafting
strategy may facilitate the development of strong wood-based composites
with interesting features.