Dielectric, dynamic mechanical and DSC evidence for a spatial and dynamic heterogeneity in a single phase polymer system

Guo, Zhao‐Xia; Browne, Emer; Compton, J.; Sautereau, H.; Kranbuehl, David E.

doi:10.1016/j.jnoncrysol.2006.01.133

Cited by 3 publications

(3 citation statements)

References 10 publications

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“…The shift of the auto-acceleration period on the reaction rate curve of TEGDMA may be considered as an evidence of increasing inhomogeneity of curing reaction. The dimethacrylate network heterogeneity is well established, in agreement with Dušek, [15], and later with others [16,17,18]. Individual micro-gel domains are formed initially around multiple initiation sites.…”

Section: Resultssupporting

confidence: 84%

Morphogenesis of Photo-Polymerized Dimethacrylate Networks, Kinetics of Curing and Viscoelastic Parameters

Bystřický

Jančář

2016

MSF

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The paper refers to the process of dimethacrylate networks morphogenesis. These stiff and highly cross-linked networks have been extensively used as a polymeric matrix of dental composites for decades. In the study, common co-monomer mixtures used in dental resin formulations were employed. This includes rigid aromatic base monomers, bisphenol A glycerolate dimethacrylate (Bis-GMA) and its ethoxylated alternative (Bis-EMA). Flexible aliphatic monomer, triethylene glycol dimethacrylate (TEGDMA), was used as the viscosity reducer. Kinetics of the polymerization process was studied regarding the structural differences and varying molar ratio of the co-monomers. Kinetic data provided the base for understanding the supra-molecular structure evolution. Consequently, an attempt to quantify the relationship between the resulting network morphology and complex viscoelastic moduli was made. Curing kinetics was studied using differential photo-calorimetry (DPC). Complex modulus was measured using dynamic-mechanical analysis (DMA). Thermal degradation kinetic data (TGA) were used in order to confirm the estimated morphology of cured networks. Reactivity of the monomer is derived from its molecular structure. The potential for non-covalent physical interactions along with monomer backbone rigidity significantly decrease polymerization rate and resulting double bond conversion. The diffusion-controlled kinetics dominates over the chemically controlled kinetics throughout most of the polymerization process. Dilution by the low viscous and flexible monomer shifts the diffusion-controlled kinetics to the later stages of the polymerization. However, the flexibility of the monomer backbone promotes the origination of structural heterogeneities, characterized by micro-gel domains formation. This is associated particularly with the anomalous pendant double bond reactivity and ineffective cross-linking.

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Section: Resultssupporting

confidence: 84%

Morphogenesis of Photo-Polymerized Dimethacrylate Networks, Kinetics of Curing and Viscoelastic Parameters

Bystřický

Jančář

2016

MSF

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“…Experimental evidence of the presence of structural microheterogeneities has been pointed out through a variety of physical methods including thermomechanical measurements, − dielectric analyses, , or spectroscopic techniques such as solid state NMR. − Nevertheless, only imaging techniques can provide unambiguous evidence of spatial heterogeneity with indications on the typical dimension and morphology of the constituting domains.…”

Section: Introductionmentioning

confidence: 99%

“…This type of mechanical limitation is particularly acute for UV-curable coatings 7 and adhesives, 8 as well as for the emerging sector of radiation-curable structural composites. 9,10 Experimental evidence of the presence of structural microheterogeneities has been pointed out through a variety of physical methods including thermomechanical measurements, [11][12][13] dielectric analyses, 14,15 or spectroscopic techniques such as solid state NMR. [16][17][18] Nevertheless, only imaging techniques can provide unambiguous evidence of spatial heterogeneity 19 with indications on the typical dimension and morphology of the constituting domains.…”

Section: Introductionmentioning

confidence: 99%

Calorimetric Characterization of the Heterogeneities Produced by the Radiation-Induced Cross-Linking Polymerization of Aromatic Diacrylates

Krzeminski

Molinari²,

Troyon³

et al. 2010

Macromolecules

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The structural heterogeneities in networks produced by UV-and by electron beam-initiated polymerization of aromatic diacrylates were unambiguously revealed by AFM imaging and studied by means of temperature-modulated differential scanning calorimetry. Two main second-order thermodynamic transitions were observed during the analysis of diacrylate networks exhibiting a fractional degree of conversion ranging from 0.1 to 0.8. The bimodal distribution of transition temperatures observed as fused peaks in the diagrams representing the differential quantity associated with the reversing heat capacity, dC p,rev /dT, was satisfactorily resolved by a two-component numerical fitting method allowing a quantitative exploitation of the data in terms of Gaussian contributions with particular central relaxation temperature and peak width affected by the gradual polymerization of the sample. The dual relaxation phenomenon was assigned to a biphasic-like structure consisting of clusters with a high cross-link density formed in continuous domain of lower monomer conversion. The evolution of the calorimetric data in the samples affords detailed information on the gradual formation of the network, with the initial broadening and final narrowing of the transition peak at high temperature related to the densely cross-linked clusters, whereas the low-temperature transition vanishes in intensity with an increasing broadening of the associated transition range. The analyses carried out in this work did not point out any influence of the UV-or EB-induced initiation mechanism of the time scale and thermal conditions of the polymerization process on the calorimetric features of the observed heterogeneities.

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Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

2012

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Objectives This overview is intended to highlight connections between monomer structure and the development of highly crosslinked photopolymer networks including the conversion dependent properties of shrinkage, modulus and stress. Methods A review is provided that combines the polymer science and dental materials literature along with examples of relevant experimental results, which include measurements of reaction kinetics, photorheology as well as polymerization shrinkage and stress. Results While new monomers are continually under development for dental materials applications, mixtures of dimethacrylate monomers persist as the most common form of dental resins used on composite restorative materials. Monomer viscosity and reaction potential is derived from molecular structure and by employing real-time near-infrared spectroscopic techniques, the development of macromolecular networks is linked to the evolution of polymerization shrinkage (measured by linometer), modulus (measured by photorheometer), and stress (measured by tensometer). Relationships between the respective polymer properties are examined. Significance Through a better understanding of the polymer network formation and property development processes using conventional dimethacrylate monomer formulations, the rational design of improved materials is facilitated with the ultimate goal of achieving dental polymers that deliver enhanced clinical outcomes.

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Dielectric, dynamic mechanical and DSC evidence for a spatial and dynamic heterogeneity in a single phase polymer system

Cited by 3 publications

References 10 publications

Morphogenesis of Photo-Polymerized Dimethacrylate Networks, Kinetics of Curing and Viscoelastic Parameters

Morphogenesis of Photo-Polymerized Dimethacrylate Networks, Kinetics of Curing and Viscoelastic Parameters

Calorimetric Characterization of the Heterogeneities Produced by the Radiation-Induced Cross-Linking Polymerization of Aromatic Diacrylates

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

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