Kinetics aspects, rheological properties and mechanoelectrical effects of hydrogels composed of polyacrylamide and polystyrene nanoparticles.
Résumé
Snake-cage gels were prepared using monodisperse polystyrene (PS) nano-size particles (R = 200 nm) in place of the more usually used linear polymer. The kinetics of the formation of the complementary polyacrylamide (PAM) hydrogel was studied alone or in the presence of the PS nanoparticles by 1H-NMR. Without PS, the reactivity ratios of the acrylamide (Am) and the crosslinking agent N,N'-methylene-bisacrylamide (BisAm) were computed using the initial kinetics of PAM gel at high crosslinker concentration (rA= 0.52, rB = 5.2, for Am and BisAm respectively). In the presence of PS, during the formation of nanoparticles composite gels (NPC gels), there was a decrease of the conversion rate with an increasing fraction of PS nanoparticles. This could be explained by steric effects which induce an increase of the elastic modulus of the matrix with the increasing fraction of PS nanoparticles. There was a considerable increase of the rheological properties of the NPC gels (i.e. tensile modulus) which was more pronounced at higher fractions of nanoparticles. We used the particular mechanical properties to develop a stimulus responsive (“smart”) material, i.e. a mechanoelectrical effect which may be used in the development of soft and wet tactile sensing devices
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