Thermoresponsive Toughening in LCST-Type Hydrogels: Comparison between Semi-Interpenetrated and Grafted Networks
Résumé
Hydrophilic and LCST polymer chains, poly(N,N-dimethylacrylamide) (PDMA) and poly(Nisopropylacrylamide)
(PNIPA), were combined in semi-interpenetrated architectures to
investigate their responsive properties in swollen isochoric conditions comparatively to
grafted network structures. Using equal weight fractions of PDMA and PNIPA, semi-IPN
designed with opposite topologies have demonstrated a thermoresponsive behavior with very
different structure/properties relationships as investigated by calorimetry, swelling
experiments, tensile tests and 2D neutron scattering at rest and under deformation. In the case
of the PDMA network interpenetrated by linear PNIPA chains, the phase transition of PNIPA
gives rise to the formation of large microdomains, loosely percolating the PDMA network.
Above the transition, the enhancement of the mechanical properties remains low in terms of
elastic modulus and fracture energy. Conversely, the opposite topology, with PDMA chains
interpenetrating the crosslinked PNIPA network, brings a large improvement of the
mechanical properties at high temperature with a 10-fold increase of the modulus and very
high fracture energy. By comparison with grafted hydrogels of similar composition and
different topologies, the impact of the primary structure over the phase-separated morphology
and the resulting mechanical properties was clearly highlighted.
Domaines
Matière Molle [cond-mat.soft]Origine | Fichiers produits par l'(les) auteur(s) |
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