Network Formation by Dimethacrylate Based Dental Resins, Evolution of the Structure and Viscoelastic Parameters

článek ve sborníku ve WoS nebo Scopus

angličtina

The submission refers to the morphogenesis of dimethacrylate networks used, inter alia, in the field of restorative dentistry. In the study, the most commonly employed monomers in the nowadays dental practice were used. This includes rigid aromatic monomers, bisphenol A glycerolate dimethacrylate (Bis-GMA), ethoxylated Bis-GMA (EPBDMA), flexible aliphatic urethane dimethacrylate (UDMA) as examples of viscous base monomers and triethylene glycol dimethacrylate (TEGDMA) as a viscosity reducer. Connections between the specific structural features of distinct monomer species, curing kinetics and viscoelastic properties are highlighted. Morphogenesis of the network was studied regarding the structural differences and a varying molar ratio of the co-monomers. Photo-polymerization kinetic data provided the base for understanding the supra-molecular structure evolution. An attempt to quantify the relationship between the network morphology and complex viscoelastic moduli has been made. Curing kinetics was studied by differential photo-calorimetry (DPC), double bond conversion was determined via infrared spectroscopy (FTIR). Viscoelastic parameters were measured using dynamic-mechanical analysis (DMA) and interpreted using the known models. Thermal degradation was investigated using thermo-gravimetric analysis (TGA). Monomer viscosity and reactivity are derived from its molecular structure. The potential for hydrogen bonding along with monomer rigidity significantly decrease polymerization rate (Rp), double bonds conversion (PC=C) and hasten the diffusion-controlled kinetics (e. g. Bis-GMA polymerization). Absence of the hydroxyl functionalities (EPBDMA) and of the rigid core structure (UDMA) results in the increase of both Rp and PC=C. Dilution by TEGDMA leads to the shift of the diffusion controlled kinetics to higher conversion. However, the flexibility of the monomer backbone promotes the origination of heterogeneities characterized by micro-gel domains formation associated particularly with the primary cyclization reactions and ineffective cross-linking. This is observed by appearance of two-step degradation process and broadening of relaxation time spectra (loss tangent peak). Coexistence of loosely cross-linked and more densely cross-linked regions in the network ultimately results in a mechanical properties reduction.

dimethacrylate monomers, tetra-functional network formation, photo-polymerization, curing kinetics, viscoelasticity

BYSTŘICKÝ, Z.; JANČÁŘ, J.

2014

4. 12. 2014

Vysoké učení technické v Brně, Fakulta chemická, Purkyňova 464/118, 612 00 Brno

Brno, Czech Republic

978-80-214-5078-3

Studentská odborná konference Chemie je život 2014

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