writer：Wang,Q.; Hou R.X.; Cheng, Y.J.; Fu, J.*
keywords：nanoparticles, double network, hydrogel, mechanical properties
source：期刊
specific source：Soft Matter 2012 8 6048-6056
Issue time：2012年

We have successfully developed hydrogels with high compressive toughness by reinforcing the doublenetwork structure (PAMPS/PAAm) with grafted silica nanoparticles. Silica nanoparticles grafted with vinyl end groups were used as macro-crosslinkers to copolymerize with AMPS, yielding a nanocomposite first network. Subsequent introduction of a secondary PAAm network resulted in
super-tough double-network (DN) composite hydrogels, which do not fracture upon loading up to 73 MPa and a strain above 0.98. The compressive strength, swelling behavior, and morphology of the silica-grafted DN hydrogels were investigated as functions of nanoparticle content and particle size, in comparison with silica nanoparticle-filled DN gels without covalent bonding to the polymer network. Maximal reinforcement of the DN gels was achieved at around 1 wt% (weight percent) of grafted silica nanoparticles with respect to AMPS. Unique embedded micro-network structures were observed in the silica-grafted DN gels and accounted for the substantial improvement in compressive toughness. The
fracture mechanism is discussed in detail based on the yielding behavior of these covalently composited hydrogels.