title: Control of hierarchical polymer mechanics with bioinspired metal-coordination dynamics.
abstract: In conventional polymer materials, mechanical performance is traditionally engineered via material structure, using motifs such as polymer molecular weight, polymer branching, or block copolymer design. Here, by means of a model system of 4-arm poly(ethylene glycol) hydrogels crosslinked with multiple, kinetically distinct dynamic metal-ligand coordinate complexes, we show that polymer materials with decoupled spatial structure and mechanical performance can be designed. By tuning the relative concentration of two types of metal-ligand crosslinks, we demonstrate control over the material's mechanical hierarchy of energy-dissipating modes under dynamic mechanical loading, and therefore the ability to engineer a priori the viscoelastic properties of these materials by controlling the types of crosslinks rather than by modifying the polymer itself. This strategy to decouple material mechanics from structure is general and may inform the design of soft materials for use in complex mechanical environments. Three examples that demonstrate this are provided.
authors: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Scott C
authors: SC
authors: Grindy
authors: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Robert
authors: R
authors: Learsch
authors: Department of Chemistry, University of California, Irvine, California 92697, USA.
authors: Davoud
authors: D
authors: Mozhdehi
authors: Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors: Jing
authors: J
authors: Cheng
authors: Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors: Devin G
authors: DG
authors: Barrett
authors: Department of Chemistry, University of California, Irvine, California 92697, USA.
authors: Zhibin
authors: Z
authors: Guan
authors: Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors: Phillip B
authors: PB
authors: Messersmith
authors: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Niels
authors: N
authors: Holten-Andersen
mesh_terms: D004548:Elasticity; D020100:Hydrogels / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D014783:Viscosity
chemical_list: D020100:Hydrogels; D008670:Metals; D011108:Polymers