Structural and Mechanical Self-healing of Physically Cross-linked Polymer Hydrogels*

Telechelic polymers with hydrophobic, ‘sticky’ end groups form micelles with polymers bridging the hydrophobic cores, resulting in a transient network gel. These gels have interesting properties such as tunable flow dynamics and ability to self-heal after mechanical disruption by molecular exchange between the micelle cores [1,2]. Studies using rheology and in combination with Small-Angle Neutron Scattering (SANS) are presented, addressing the structure of the polymer chains and the crystalline structure of the micelle cores in the gel, using selective deuteration. The gel is disrupted by oscillatory strain, and self-heals on a time scale from seconds to tens of minutes. Different recovery patterns are observed for a gel that is liqueified by the strain vs. a gel that remains solid under strain. The results show how the mechanical and the structural recovery are linked and highly dependent on the processing history of the gel.

1. Zinn T, Willner L, Lund R, Pipich V, Richter D, Soft Matter 2012; 8: 623-626.
2. Zinn T, Willner L, Lund R, ACS Macro Lett 2016; 5(12): 1353-1356.