IADR Abstract Archives
Kinetics of Photo-“click” CuAAC Polymers for Dental Resins
Objectives: Current methacrylate-based dental resins are incapable of forming homogeneous networks with full conversion due to the nature of chain growth polymerizations. Polymers made from a step growth polymerization of photo-“click” CuAAC, copper-catalyzed azide-alkyne cycloaddition, polymerization may solve these issues and provide an innovative approach for future generations of dental resins. This study focused on determining the effects on conversion and photo-CuAAC polymerization rates as dictated by key monomer structural features. This structure-property relationship will enable determination of optimal structural features to include in monomers.
Methods: Numerous structures of di-functional azides and tri-functional alkynes were synthesized with variability in both the rigidity of cores and backbones of monomers while assuring the formation of stable azides. In situ polymerization kinetics were monitored using a ThermoScientific FTIR (Fourier transform infrared spectroscopy) incorporated with a heating stage. Disappearance of the azide moieties was monitored to calculate conversion and initial polymerization rates in triplicate.
Results: Increasing the stiffness of monomer core structures from dicyclohexane to dibenzene decreased average initial polymerization rate from 47±2 to 33±6 %conversion per minutes and maximum conversion from 82±1 to 75±3% at 50°C. Also, increasing number of cyclohexane cores from cyclohexane to dicyclohexane decreased average initial polymerization rate from 60±6 to 47±2 %conversion per minutes and maximum conversion from 95±1 to 82±1% at 50°C. Additionally, less flexible carbamate functional groups compared to ethers in the monomer backbones reduced average polymerization rate from 82±21 to 33±6 %conversion per minutes and maximum conversion from 96±1 to 75±3% at 50°C.
Conclusions: Structural elements of both the azide and alkyne monomers were found to be critical in controlling both polymerization rates and final conversion. Appropriate selection of monomers enabled the photo-CuAAC polymerization reactions to be completed rapidly and to reach high conversion as needed for dental restorative materials.
Methods: Numerous structures of di-functional azides and tri-functional alkynes were synthesized with variability in both the rigidity of cores and backbones of monomers while assuring the formation of stable azides. In situ polymerization kinetics were monitored using a ThermoScientific FTIR (Fourier transform infrared spectroscopy) incorporated with a heating stage. Disappearance of the azide moieties was monitored to calculate conversion and initial polymerization rates in triplicate.
Results: Increasing the stiffness of monomer core structures from dicyclohexane to dibenzene decreased average initial polymerization rate from 47±2 to 33±6 %conversion per minutes and maximum conversion from 82±1 to 75±3% at 50°C. Also, increasing number of cyclohexane cores from cyclohexane to dicyclohexane decreased average initial polymerization rate from 60±6 to 47±2 %conversion per minutes and maximum conversion from 95±1 to 82±1% at 50°C. Additionally, less flexible carbamate functional groups compared to ethers in the monomer backbones reduced average polymerization rate from 82±21 to 33±6 %conversion per minutes and maximum conversion from 96±1 to 75±3% at 50°C.
Conclusions: Structural elements of both the azide and alkyne monomers were found to be critical in controlling both polymerization rates and final conversion. Appropriate selection of monomers enabled the photo-CuAAC polymerization reactions to be completed rapidly and to reach high conversion as needed for dental restorative materials.