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Kinetics of thiol–ene and thiol–acrylate photopolymerizations with real-time fourier transform infrared

Authors

  • Neil B. Cramer,

    1. Department of Chemical Engineering, University of Colorado, Boulder, Colorado 80309-0424
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  • Christopher N. Bowman

    Corresponding author
    1. Department of Chemical Engineering, University of Colorado, Boulder, Colorado 80309-0424
    2. Department of Restorative Dentistry, University of Colorado Health Sciences Center, Denver, Colorado, 80045-0508
    • Department of Chemical Engineering, University of Colorado, Boulder, Colorado 80309-0424
    Search for more papers by this author

Abstract

We used real-time Fourier transform infrared to monitor the conversion of both thiol and ene (vinyl) functional groups independently during photoinduced thiol–ene photopolymerizations. From these results, the stoichiometry of various thiol–ene and thiol–acrylate polymerizations was determined. For thiol–ene polymerizations, the conversion of ene functional groups was up to 15% greater than the conversion of thiol functional groups. For stoichiometric thiol–acrylate polymerizations, the conversion of the acrylate functional groups was roughly twice that of the thiol functional groups. With kinetic expressions for thiol–acrylate polymerizations, the acrylate propagation kinetic constant was found to be 1.5 times greater than the rate constant for hydrogen abstraction from the thiol. Conversions of thiol–acrylate systems of various initial stoichiometries were successfully predicted with this ratio of propagation and chain-transfer kinetic constants. Thiol–acrylate systems with different initial stoichiometries exhibited diverse network properties. Thiol–ene systems were initiated with benzophenone and 2,2-dimethoxy-2-phenylacetophenone as initiators and were also polymerized without a photoinitiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3311–3319, 2001

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