title: Highly branched and loop-rich gels via formation of metal-organic cages linked by polymers.
abstract: Gels formed via metal-ligand coordination typically have very low branch functionality, f, as they consist of ∼2-3 polymer chains linked to single metal ions that serve as junctions. Thus, these materials are very soft and unable to withstand network defects such as dangling ends and loops. We report here a new class of gels assembled from polymeric ligands and metal-organic cages (MOCs) as junctions. The resulting 'polyMOC' gels are precisely tunable and may feature increased branch functionality. We show two examples of such polyMOCs: a gel with a low f based on a M2L4 paddlewheel cluster junction and a compositionally isomeric one of higher f based on a M12L24 cage. The latter features large shear moduli, but also a very large number of elastically inactive loop defects that we subsequently exchanged for functional ligands, with no impact on the gel's shear modulus. Such a ligand substitution is not possible in gels of low f, including the M2L4-based polyMOC.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Aleksandr V
authors.initials: AV
authors.lastname: Zhukhovitskiy
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Mingjiang
authors.identifier: http://orcid.org/0000-0001-7533-4708
authors.initials: M
authors.lastname: Zhong
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Eric G
authors.identifier: http://orcid.org/0000-0002-9598-7148
authors.initials: EG
authors.lastname: Keeler
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Vladimir K
authors.identifier: http://orcid.org/0000-0002-6708-7660
authors.initials: VK
authors.lastname: Michaelis
authors.affiliation: Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716, USA.
authors.forename: Jessie E P
authors.initials: JE
authors.lastname: Sun
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
authors.forename: Michael J A
authors.initials: MJ
authors.lastname: Hore
authors.affiliation: Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716, USA.
authors.forename: Darrin J
authors.initials: DJ
authors.lastname: Pochan
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.|Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Griffin
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Willard
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Jeremiah A
authors.identifier: http://orcid.org/0000-0001-9157-6491
authors.initials: JA
authors.lastname: Johnson
mesh_terms: D004548:Elasticity; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D056004:Molecular Dynamics Simulation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D005782:Gels; D008024:Ligands; D009942:Organometallic Compounds; D011108:Polymers