Thiol−Allyl Ether−Methacrylate Ternary Systems. Evolution Mechanism of Polymerization-Induced Shrinkage Stress and Mechanical Properties

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 systemsa methacrylate homopolymerization regime followed by a thiol−ene polymerization dominated regimethe 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 systems. Also, because of the two polymerization regimes, the mechanical properties evolve uniquely as compared to other ternary systems. It is noted that glass transition temperatures of the ternary systems (∼100 °C) are much higher than traditional thiol−ene polymers and comparable to the current polymeric composites for dental restorations, indicating that the thiol−allyl ether−methacrylate systems are an excellent candidate for dental restorations.

Chemical functionalization of emulsion-templated porous polymers by thiol–ene “click” chemistry

“…Consequently, if the acrylates were consumed solely by reaction with thiols, no residual thiol groups should be present in the cured materials. Since the 40 and 50% samples show significant levels of residual thiol (Table 1) we can conclude that another reaction that consumes acrylates is occuring, most probably acrylate homopolymerisation 19,20 . The stiffness of the samples was observed (by tactile inspection) to increase as the ratio of acrylate : thiol increased.…”

“…Solid-state 19 F NMR spectra were obtained using a Varian VNMRS 400 spectrometer using a direct polarisation experiment at a frequency of 282.087 MHz. Solid-state 13 C NMR spectra were obtained using a Varian VNMRS 400 spectrometer using a direct polarisation experiment at a frequency of 100.56 MHz.…”

“…The quantity of acrylate used was calculated as 2 equivalents relative to the highest residual thiol content determined ( Table 1). The functionalized samples were analysed by 19 F NMR spectroscopy, 13 C NMR spectroscopy and XPS. HFIPA was chosen due to its high fluorine content, which can be detected by 19 F NMR spectroscopy and by XPS.…”

“…Two competing reactions occur during the formation of thiolacrylate polymer networks; that between thiols and C=C bonds (enes); and acrylate-acrylate homopolymerization 19,20 (Scheme 1). The latter leads to the presence of unreacted thiols in the polyHIPE.…”

The effect of a dithiol spiroorthocarbonate on mechanical properties and shrinkage of a dental resin

“…Nonetheless, the reduction in volume shrinkage in thiol-ene systems implies a reduction in cross-link density; therefore, one of the drawbacks of thiol-ene systems is that they generally exhibit reduced mechanical properties in comparison with dimethacrylate-based systems. [14] For this reason, the addition of a thiol-ene system to a conventional dimethacrylate dental resin has been attempted. [15][16][17] In this study, a novel SOC, the 1,4,6,9-tetraoxaspiro [4.4] nonane-2,7-diyldimethanethiol (SOC DITHIOL) was synthesized, characterized, and used in a typical dimethacrylate system Bis-GMA-TEGDMA-UDMA.…”