Molecular engineering of fracture energy dissipating sacrificial bonds into cellulose nanocrystal nanocomposites.
Even though nanocomposites have provided a plethora of routes to increase stiffness and strength, achieving increased toughness with suppressed catastrophic crack growth has remained more challenging. Inspired by the concepts of mechanically excellent natural nanomaterials, one-component nanocomposites were fabricated involving reinforcing colloidal nanorod cores with polymeric grafts containing supramolecular binding units. The concept is based on mechanically strong native cellulose nanocrystals (CNC) grafted with glassy polymethacrylate polymers, with side chains that contain 2-ureido-4[1H]-pyrimidone (UPy) pendant groups. The interdigitation of the grafts and the ensuing UPy hydrogen bonds bind the nanocomposite network together. Under stress, UPy groups act as sacrificial bonds: simultaneously providing adhesion between the CNCs while allowing them to first orient and then gradually slide past each other, thus dissipating fracture energy. We propose that this architecture involving supramolecular binding units within side chains of polymer grafts attached to colloidal reinforcements opens generic approaches for tough nanocomposites.
Molecular Materials, Department of Applied Physics, Aalto University School of Science and Technology (previously Helsinki University of Technology), P.O. Box 15100, 00076 Aalto, Espoo (Finland) http://physics.aalto.fi/groups/molmat/
Jason R
JR
McKee
Johannes
J
Huokuna
Lahja
L
Martikainen
Mikko
M
Karesoja
Antti
A
Nykänen
Eero
E
Kontturi
Heikki
H
Tenhu
Janne
J
Ruokolainen
Olli
O
Ikkala
D002482:Cellulose / Q000737:chemistry*; D006860:Hydrogen Bonding; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*
D002482:Cellulose
biomimetic materials; cellulose nanocrystals; nanocomposite; supramolecular chemistry