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Christopher N. Bowman - One of the best experts on this subject based on the ideXlab platform.

  • Reduced Shrinkage Stress via photo-initiated copper(I)-catalyzed cycloaddition polymerizations of azide-alkyne resins
    Dental materials : official publication of the Academy of Dental Materials, 2016
    Co-Authors: Han Byul Song, Jeffrey W. Stansbury, Parag K. Shah, Nancy Sowan, Austin Baranek, Alexander Flores, Christopher N. Bowman
    Abstract:

    Abstract Objectives Polymerization Shrinkage Stress and factors involved in the Stress development such as volumetric Shrinkage and modulus were investigated in photo-CuAAC (photo-initiated copper(I)-catalyzed azide-alkyne cycloaddition) polymerization and compared with conventional BisGMA-based methacrylate polymerization for their use as alternative dental resins. Methods Tri-functional alkyne and di-functional azide monomers were synthesized for photo-CuAAC polymerization. Conversion kinetics, Stress development and polymerization Shrinkage were determined with FTIR spectroscopy, tensometery, and with a linometer, respectively, for CuAAC and BisGMA-based monomer mixtures using a camphorquinone/amine visible light photoinitiator system. Thermo-mechanical properties for the cured polymer matrices were characterized by dynamic mechanical analysis and in three-point bending on a universal testing machine. Polymerization kinetics, polymerization Shrinkage Stress, dynamic volumetric Shrinkage, glass transition temperature (Tg), flexural modulus, flexural strength, and flexural toughness were compared between the two different resin systems. Results A glassy CuAAC polymer (Tg = 62 °C) exhibited 15–25% lower flexural modulus of 2.5 ± 0.2 GPa and flexural strength of 117 ± 8 MPa compared to BisGMA-based polymer (Tg = 160 °C) but showed considerably higher energy absorption around 7.1 MJ × m−3 without fracture when strained to 11% via three-point bend compared to the flexural toughness of 2.7 MJ × m−3 obtained from BisGMA-based polymer. In contrast to BisGMA-based polymers at 75% functional group conversion, the CuAAC polymerization developed approximately three times lower Shrinkage Stress with the potential to achieve quantitative conversion under ambient temperature photocuring conditions. Moreover, relatively equivalent dynamic volumetric Shrinkage of around 6–7% was observed via both CuAAC and dimethacrylate polymerization, suggesting that the low Shrinkage Stress of CuAAC polymerization was due to delayed gelation along with slower rate of polymerization and the formation of a more compliant network structure. Significance CuAAC crosslinked networks possessed high toughness and low polymerization Shrinkage Stress with quantitative conversion, which eliminated obstacles associated with BisGMA-based dental resins including limited conversion, unreacted extractable moieties, brittle failure, and high Shrinkage Stress.

  • Using hyperbranched oligomer functionalized glass fillers to reduce Shrinkage Stress
    Dental materials : official publication of the Academy of Dental Materials, 2012
    Co-Authors: Setareh Azarnoush, Jeffrey W. Stansbury, Neil B Cramer, Ian R Smith, Christopher N. Bowman
    Abstract:

    Objective Fillers are widely utilized to enhance the mechanical properties of polymer resins. However, polymerization Stress has the potential to increase due to the higher elastic modulus achieved upon filler addition. Here, we demonstrate a hyperbranched oligomer functionalized glass filler UV curable resin composite which is able to reduce the Shrinkage Stress without sacrificing mechanical properties.

  • reducing Shrinkage Stress of dimethacrylate networks by reversible addition fragmentation chain transfer
    Macromolecular Chemistry and Physics, 2012
    Co-Authors: Diana Leung, Christopher N. Bowman
    Abstract:

    The trithiocarbonate 1a reduces the volumetric Shrinkage Stress in crosslinked multi(meth)acrylate networks by promoting a reversible, free-radical-mediated network rearrangement that enables network adaptation and Stress relaxation. Addition of 1a or 1b into a dimethacrylate system is examined by FT-IR. The polymerization rate is reduced in samples containing 1a, indicating a changed polymerization mechanism. The volumetric Shrinkage Stress is reduced by more than 50% compared to a pure dimethacrylate system with the addition of as little as 2 wt% of 1a, while maintaining the favorable mechanical properties of the methacrylate-crosslinked networks. No synthetic modification of the methacrylate monomer units is needed, allowing for adaptation to almost any radically polymerized system.

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol–yne–methacrylate and thiol–yne–acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol–yne and (meth)acrylate systems. Both thiol–yne–methacrylate and thiol–yne–acrylate systems were demonstrated to reduce polymerization-induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (Tg) and moduli. Formulations with 70 wt % methacrylate increased the Tg from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol–yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol–yne, and thiol–ene–methacrylate control systems which are all >2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt % methacryla...

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (T(g)) and modulius. Formulations with 70 wt% methacrylate increased the T(g) from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol-yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol-yne and thiol-ene-methacrylate control systems which are all > 2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt% methacrylate and 70 wt% acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol-yne step-growth polymerization. The crosslinking density of the networks and the amount of volumetric Shrinkage that occurs prior to gelation relative to the total volumetric Shrinkage were determined as two key factors that control the final Shrinkage Stress of the ternary systems.

Neil B Cramer - One of the best experts on this subject based on the ideXlab platform.

  • Using hyperbranched oligomer functionalized glass fillers to reduce Shrinkage Stress
    Dental materials : official publication of the Academy of Dental Materials, 2012
    Co-Authors: Setareh Azarnoush, Jeffrey W. Stansbury, Neil B Cramer, Ian R Smith, Christopher N. Bowman
    Abstract:

    Objective Fillers are widely utilized to enhance the mechanical properties of polymer resins. However, polymerization Stress has the potential to increase due to the higher elastic modulus achieved upon filler addition. Here, we demonstrate a hyperbranched oligomer functionalized glass filler UV curable resin composite which is able to reduce the Shrinkage Stress without sacrificing mechanical properties.

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol–yne–methacrylate and thiol–yne–acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol–yne and (meth)acrylate systems. Both thiol–yne–methacrylate and thiol–yne–acrylate systems were demonstrated to reduce polymerization-induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (Tg) and moduli. Formulations with 70 wt % methacrylate increased the Tg from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol–yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol–yne, and thiol–ene–methacrylate control systems which are all >2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt % methacryla...

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (T(g)) and modulius. Formulations with 70 wt% methacrylate increased the T(g) from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol-yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol-yne and thiol-ene-methacrylate control systems which are all > 2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt% methacrylate and 70 wt% acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol-yne step-growth polymerization. The crosslinking density of the networks and the amount of volumetric Shrinkage that occurs prior to gelation relative to the total volumetric Shrinkage were determined as two key factors that control the final Shrinkage Stress of the ternary systems.

Katerina R Voigt - One of the best experts on this subject based on the ideXlab platform.

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol–yne–methacrylate and thiol–yne–acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol–yne and (meth)acrylate systems. Both thiol–yne–methacrylate and thiol–yne–acrylate systems were demonstrated to reduce polymerization-induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (Tg) and moduli. Formulations with 70 wt % methacrylate increased the Tg from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol–yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol–yne, and thiol–ene–methacrylate control systems which are all >2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt % methacryla...

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (T(g)) and modulius. Formulations with 70 wt% methacrylate increased the T(g) from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol-yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol-yne and thiol-ene-methacrylate control systems which are all > 2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt% methacrylate and 70 wt% acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol-yne step-growth polymerization. The crosslinking density of the networks and the amount of volumetric Shrinkage that occurs prior to gelation relative to the total volumetric Shrinkage were determined as two key factors that control the final Shrinkage Stress of the ternary systems.

Ian R Smith - One of the best experts on this subject based on the ideXlab platform.

  • Using hyperbranched oligomer functionalized glass fillers to reduce Shrinkage Stress
    Dental materials : official publication of the Academy of Dental Materials, 2012
    Co-Authors: Setareh Azarnoush, Jeffrey W. Stansbury, Neil B Cramer, Ian R Smith, Christopher N. Bowman
    Abstract:

    Objective Fillers are widely utilized to enhance the mechanical properties of polymer resins. However, polymerization Stress has the potential to increase due to the higher elastic modulus achieved upon filler addition. Here, we demonstrate a hyperbranched oligomer functionalized glass filler UV curable resin composite which is able to reduce the Shrinkage Stress without sacrificing mechanical properties.

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol–yne–methacrylate and thiol–yne–acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol–yne and (meth)acrylate systems. Both thiol–yne–methacrylate and thiol–yne–acrylate systems were demonstrated to reduce polymerization-induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (Tg) and moduli. Formulations with 70 wt % methacrylate increased the Tg from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol–yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol–yne, and thiol–ene–methacrylate control systems which are all >2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt % methacryla...

  • reaction kinetics and reduced Shrinkage Stress of thiol yne methacrylate and thiol yne acrylate ternary systems
    Macromolecules, 2011
    Co-Authors: Neil B Cramer, Ian R Smith, Katerina R Voigt, Christopher N. Bowman
    Abstract:

    Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced Shrinkage Stress while simultaneously achieving high glass transition temperatures (T(g)) and modulius. Formulations with 70 wt% methacrylate increased the T(g) from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol-yne system. Additionally, the Shrinkage Stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol-yne and thiol-ene-methacrylate control systems which are all > 2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the Shrinkage Stress values were observed. A minimum Shrinkage Stress value (1.0 ± 0.2 MPa) was observed in the 50 wt% methacrylate and 70 wt% acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol-yne step-growth polymerization. The crosslinking density of the networks and the amount of volumetric Shrinkage that occurs prior to gelation relative to the total volumetric Shrinkage were determined as two key factors that control the final Shrinkage Stress of the ternary systems.

Tai Yeon Lee - One of the best experts on this subject based on the ideXlab platform.

  • thiol allyl ether methacrylate ternary systems evolution mechanism of polymerization induced Shrinkage Stress and mechanical properties
    Macromolecules, 2007
    Co-Authors: Tai Yeon Lee, Jacquelyn A. Carioscia, Zachary Smith, Christopher N. Bowman
    Abstract:

    The evolution of the polymerization-induced Shrinkage Stress and mechanical properties of thiol−allyl ether−methacrylate ternary systems and their relationship to the polymerization kinetics have been investigated. Because of the two distinct polymerization regimes of the ternary systemsa methacrylate homopolymerization regime followed by a thiol−ene polymerization dominated regimethe mechanism for the evolution of polymerization induced Shrinkage Stress is unique as compared to other thiol−ene and methacrylate systems. During the first polymerization stage, only intermediate molecular weight methacrylate oligomers are produced, resulting in delayed gelation and near zero Shrinkage Stress. Immediately following the first polymerization stage, the allyl ether begins to polymerize, and Shrinkage Stress increases in correspondence with the increased allyl ether conversion. It is observed that the Shrinkage Stress of the ternary systems exhibits ∼50% of the Shrinkage Stress of the current dental restoration s...

  • Thiol−Allyl Ether−Methacrylate Ternary Systems. Evolution Mechanism of Polymerization-Induced Shrinkage Stress and Mechanical Properties
    Macromolecules, 2007
    Co-Authors: Tai Yeon Lee, Jacquelyn A. Carioscia, Zachary Smith, Christopher N. Bowman
    Abstract:

    The evolution of the polymerization-induced Shrinkage Stress and mechanical properties of thiol−allyl ether−methacrylate ternary systems and their relationship to the polymerization kinetics have been investigated. Because of the two distinct polymerization regimes of the ternary systemsa methacrylate homopolymerization regime followed by a thiol−ene polymerization dominated regimethe mechanism for the evolution of polymerization induced Shrinkage Stress is unique as compared to other thiol−ene and methacrylate systems. During the first polymerization stage, only intermediate molecular weight methacrylate oligomers are produced, resulting in delayed gelation and near zero Shrinkage Stress. Immediately following the first polymerization stage, the allyl ether begins to polymerize, and Shrinkage Stress increases in correspondence with the increased allyl ether conversion. It is observed that the Shrinkage Stress of the ternary systems exhibits ∼50% of the Shrinkage Stress of the current dental restoration s...