Topology-Specific Injectable Sticky Hydrogels

Mehdi Vahdati (1) , Guylaine Ducouret (1) , Costantino Creton (1) , Dominique Hourdet (1)

1 SIMM - Sciences et Ingénierie de la Matière Molle (UMR 7615)

Stimuli-responsive injectable hydrogels based on weak supramolecular interactions may represent safer alternatives to 4 chemically reactive adhesive hydrogels for biomedical applications where weak to moderate adhesion is required. We investigated the 5 linear and nonlinear rheological properties as well as the adhesive properties of two thermoresponsive graft copolymers with inverse 6 topologies, poly(N-isopropyl acrylamide)-g-poly(N,N-dimethylacrylamide) (PNIPAM-g-PDMA) and PDMA-g-PNIPAM. Except for 7 their topologies, these copolymers are analogous in terms of chemistry, architecture (graft), and monomer composition (50−50 wt 8 %). Over a wide range of concentrations, they both form injectable homogeneous solutions at room temperature and turn into soft 9 and sticky viscoelastic hydrogels close to body temperature. We find that the linear viscoelastic properties of these two hydrogels are 10 not discernible far above the thermal transition temperature. However, the PNIPAM-g-PDMA hydrogel having long 11 thermoresponsive backbones shows a strain-hardening behavior in large strains both in probe tack tests and in shear. The inverse 12 topology, PDMA-g-PNIPAM, showed no hardening and simply softened until failure. This distinction was observed regardless of the 13 polymer concentration (in the entangled regime). We attribute the hardening to a continuous, load-bearing nanostructure from 14 strong hydrophobic PNIPAM associations, while the softening is due to the easy pullout of short PNIPAM grafts from separate 15 hydrophobic clusters bridged by PDMA backbones. The findings of this work highlight the importance of macromolecular design in 16 determining the nanostructure and thereby the mechanical performance of soft hydrogels for specific applications.

Domaines: Matière Molle [cond-mat.soft]; Matière Condensée [cond-mat]

Mehdi Vahdati, Guylaine Ducouret, Costantino Creton, Dominique Hourdet. Topology-Specific Injectable Sticky Hydrogels. Macromolecules, 2020, ⟨10.1021/acs.macromol.0c01826⟩. ⟨hal-03007307⟩