title: Tough stimuli-responsive supramolecular hydrogels with hydrogen-bonding network junctions.
abstract: Hydrogels were prepared with physical cross-links comprising 2-ureido-4[1H]-pyrimidinone (UPy) hydrogen-bonding units within the backbone of segmented amphiphilic macromolecules having hydrophilic poly(ethylene glycol) (PEG). The bulk materials adopt nanoscopic physical cross-links composed of UPy-UPy dimers embedded in segregated hydrophobic domains dispersed within the PEG matrix as comfirmed by cryo-electron microscopy. The amphiphilic network was swollen with high weight fractions of water (w(H2O) ≈ 0.8) owing to the high PEG weight fraction within the pristine polymers (w(PEG) ≈ 0.9). Two different PEG chain lengths were investigated and illustrate the corresponding consequences of cross-link density on mechanical properties. The resulting hydrogels exhibited high strength and resilience upon deformation, consistent with a microphase separated network, in which the UPy-UPy interactions were adequately shielded within hydrophobic nanoscale pockets that maintain the network despite extensive water content. The cumulative result is a series of tough hydrogels with tunable mechanical properties and tractable synthetic preparation and processing. Furthermore, the melting transition of PEG in the dry polymer was shown to be an effective stimulus for shape memory behavior.
authors.affiliation: Institute for Complex Molecular Systems, ‡Laboratory of Chemical Biology, §Department of Chemistry and Chemical Engineering, ∥Department of Mechanical Engineering, Eindhoven University of Technology , P.O. Box 513, NL 5600 MB Eindhoven, The Netherlands.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Guo
authors.forename: Louis M
authors.initials: LM
authors.lastname: Pitet
authors.forename: Hans M
authors.initials: HM
authors.lastname: Wyss
authors.forename: Matthijn
authors.initials: M
authors.lastname: Vos
authors.forename: Patricia Y W
authors.initials: PY
authors.lastname: Dankers
authors.forename: E W
authors.initials: EW
authors.lastname: Meijer
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry; D020285:Cryoelectron Microscopy; D019281:Dimerization; D020100:Hydrogels / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D055595:Mechanical Phenomena; D011092:Polyethylene Glycols / Q000737:chemistry*; D011744:Pyrimidinones / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: C029046:2-ureido-4(3H)-pyrimidinone; D003432:Cross-Linking Reagents; D020100:Hydrogels; D011744:Pyrimidinones; D014867:Water; D011092:Polyethylene Glycols