polymersolutions.Weexpectthattherearemanymonomersadsorbed per strand, n?1, and that for nanoparticles with diameters compar- able with the network mesh size, several different network strands are adsorbed to the same particle18. Thus, in the adhesive layer, nanopar- ticlesactasconnectorsbetweengelpiecesandgel-chainsactasbridges between different particles (Fig. 1a). When the adhesive junction is strained,adsorbedchainsareundertension(forexample,theredchain in Fig. 1b) and some adsorbed monomers detach from the particle surface and relax the tension. Nanoparticles retard failure and ensure goodadhesionbecausetheenergydissipatedduringthestress-induced desorption process is much greater than e. Indeed, detaching only one1Physico-chimie des Polyme `res et Milieux Disperse ´s (UMR7615 UPMC/ESPCI/CNRS), Universite ´ Pierre et Marie Curie, E ´cole Supe ´rieure de Physique et de Chimie industrielles, 75005 Paris, France. 2Matie `re Molle et Chimie (UMR 7167 CNRS/ESPCI), E ´cole Supe ´rieure de Physique et de Chimie Industrielles, 75005 Paris, France.abFigure 1 | Gluing gels by nanoparticle solutions. a, Schematic illustration of the concept of gluing swollen polymer networks together using particles. The nanoparticle diameter is comparable with the gel network mesh size. Network chains are adsorbed on nanoparticles and anchor particles to gel pieces. Particles act as connectors between gel surfaces. Adsorbed chains also form bridges between particles. The black arrows indicate the pressure applied to squeeze the gel layers together. b, Particle adsorption is irreversible because particles are anchored to the gel networks by numerous attachments (red, light- and dark-blue strands). At equilibrium or under tension (indicated by black arrows) a monomer that detaches from a particle surface (red strand) can be replaced by a monomer belonging to the same or a different network strand (shown here as a dark-blue strand). Such exchange processes and rearrangements allow for large deformations and energy dissipation under stress.
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