title: Living Additive Manufacturing: Transformation of Parent Gels into Diversely Functionalized Daughter Gels Made Possible by Visible Light Photoredox Catalysis.
abstract: Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials "dead" toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative "living additive manufacturing" strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant "parent" materials to generate more complex and diversely functionalized "daughter" materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent's average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.
authors.affiliation: Department of Chemistry and Department of Chemical Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Mao
authors.initials: M
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Department of Chemical Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Chemical Engineering Department, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Awaneesh
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Chemistry and Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States; Department of Chemistry and Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Mingjiang
authors.initials: M
authors.lastname: Zhong
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Jordan
authors.affiliation: Chemical Engineering Department, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Santidan
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University , Cleveland, Ohio 44106, United States.
authors.forename: LaShanda T J
authors.initials: LT
authors.lastname: Korley
authors.affiliation: Chemical Engineering Department, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Balazs
authors.affiliation: Department of Chemistry and Department of Chemical Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Jeremiah A
authors.initials: JA
authors.lastname: Johnson