title: Photoinduced plasticity in cross-linked polymers.
abstract: Chemically cross-linked polymers are inherently limited by stresses that are introduced by post-gelation volume changes during polymerization. It is also difficult to change a cross-linked polymer's shape without a corresponding loss of material properties or substantial stress development. We demonstrate a cross-linked polymer that, upon exposure to light, exhibits stress and/or strain relaxation without any concomitant change in material properties. This result is achieved by introducing radicals via photocleavage of residual photoinitiator in the polymer matrix, which then diffuse via addition-fragmentation chain transfer of midchain functional groups. These processes lead to photoinduced plasticity, actuation, and equilibrium shape changes without residual stress. Such polymeric materials are critical to the development of microdevices, biomaterials, and polymeric coatings.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Scott
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Schneider
authors.forename: Wayne D
authors.initials: WD
authors.lastname: Cook
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Bowman
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives* / Q000737:chemistry*; D034242:Cyclooctanes / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D005026:Ethylene Glycols / Q000737:chemistry*; D008027:Light; D011108:Polymers / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D013314:Stress, Mechanical; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013696:Temperature; D013718:Tensile Strength
chemical_list: C501432:2-methyl-7-methylene-1,5-dithiacyclooctane; D034242:Cyclooctanes; D004987:Ethers; D005026:Ethylene Glycols; D011108:Polymers; D011409:Propylene Glycols; D013438:Sulfhydryl Compounds; C501435:pentaerythritol tetra(3-mercaptopropionate); C501434:triethyleneglycol divinylether; D015097:3-Mercaptopropionic Acid; C501433:1,6-hexanedithiol