title: Kinetics and mechanics of photo-polymerized triazole-containing thermosetting composites via the copper(I)-catalyzed azide-alkyne cycloaddition.
abstract: Several features necessary for polymer composite materials in practical applications such as dental restorative materials were investigated in photo-curable CuAAC (copper(I)-catalyzed azide-alkyne cycloaddition) thermosetting resin-based composites with varying filler loadings and compared to a conventional BisGMA/TEGDMA based composite.
  
  
  
  Tri-functional alkyne and di-functional azide monomers were synthesized for CuAAC resins and incorporated with alkyne-functionalized glass microfillers for CuAAC composites. Polymerization kinetics, in situ temperature change, and shrinkage stress were monitored simultaneously with a tensometer coupled with FTIR spectroscopy and a data-logging thermocouple. The glass transition temperature was analyzed by dynamic mechanical analysis. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine.
  
  
  
  The photo-CuAAC polymerization of composites containing between 0 and 60wt% microfiller achieved ∼99% conversion with a dramatic reduction in the maximum heat of reaction (∼20°C decrease) for the 60wt% filled CuAAC composites as compared with the unfilled CuAAC resin. CuAAC composites with 60wt% microfiller generated more than twice lower shrinkage stress of 0.43±0.01MPa, equivalent flexural modulus of 6.1±0.7GPa, equivalent flexural strength of 107±9MPa, and more than 10 times higher energy absorption of 10±1MJm-3when strained to 11% relative to BisGMA-based composites at equivalent filler loadings.
  
  
  
  Mechanically robust and highly tough, photo-polymerized CuAAC composites with reduced shrinkage stress and a modest reaction exotherm were generated and resulted in essentially complete conversion.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO, United States.
authors.forename: Han Byul
authors.initials: HB
authors.lastname: Song
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO, United States.
authors.forename: Xiance
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: Patton
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO, United States; Department of Craniofacial Biology, School of Dental Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Stansbury
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, Boulder, CO, United States. Electronic address: Christopher.bowman@colorado.edu.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Bowman
mesh_terms: D000480:Alkynes; D001386:Azides; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D003300:Copper; D061565:Cycloaddition Reaction; D007700:Kinetics; D008422:Materials Testing; D008689:Methacrylates; D018583:Pliability; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D013314:Stress, Mechanical; D014230:Triazoles
chemical_list: D000480:Alkynes; D001386:Azides; D003188:Composite Resins; D008689:Methacrylates; D011109:Polymethacrylic Acids; D014230:Triazoles; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D003300:Copper
keywords: Click chemistry; Composites; CuAAC; Dental materials; Flexural strength; Modulus; Photopolymerization; Step-growth polymerization; Stress; Toughness