Probing stress relaxation behavior in glassy methacrylate networks containing thio-carbamate additives

Abstract

Objective: The incorporation of thiourethane prepolymer (TU) into either the organic phase or as a surface treatment for filler particles in composites reduces polymerization stress and improves fracture toughness. The...

Engineering a new generation of thermoset self-healing polymers based on intrinsic approaches

“… 34 – 40 Although delayed gelation or vitrification through chain transfer reactions via the pendant thiols is most likely the main mechanism involved in the relief of stresses generated during the polymerization, the significant increase in toughness and more recent stress-relaxation results suggest that sulfur bond dynamics can potentially also play a role. 41 Studies from other fields have shown that several associative and dissociative reversible reactions take place in thiourethane polymeric networks, such as associative thiol-thiourethane exchange, 27 associative disulfide exchange, 25 associative exchange trans-thio-carbamoylation, 42 , 43 and dissociative thiol-isocyanate. 27 Although in these studies lower Tg networks were used overall, for dental applications, these strategies will replace only a part of the organic matrix or be localized at the filler interface, which, as mentioned, has been shown to be feasible.…”

“… 27 Although in these studies lower Tg networks were used overall, for dental applications, these strategies will replace only a part of the organic matrix or be localized at the filler interface, which, as mentioned, has been shown to be feasible. 41 …”

“… 77 Another interesting approach, which combines covalent bond and supramolecular network-based strategies, is to incorporate low Tg dynamic networks as additives or filler particle functionalizing agents and use catalysts or stoichiometric imbalances to promote autonomic bond reprocess-ability. 40 , 41 , 78 As already mentioned, this strategy has been used to incorporate thiourethane into dental resin composite formulations with high toughness and intrinsic stress-relaxation mechanisms. 41 The dynamic and self-healing character of the thiourethane networks has been extensively explored in other fields, 79 , 80 but specifically, in the case of BisGMA- and urethane dimethacrylate–containing organic matrixes in dental composites, the thio-carbamate bonds also improve hydrogen bonding, and because the low Tg, flexible oligomers are swollen by the matrix, they may provide localized intermolecular reinforcement.…”

“… 40 , 41 , 78 As already mentioned, this strategy has been used to incorporate thiourethane into dental resin composite formulations with high toughness and intrinsic stress-relaxation mechanisms. 41 The dynamic and self-healing character of the thiourethane networks has been extensively explored in other fields, 79 , 80 but specifically, in the case of BisGMA- and urethane dimethacrylate–containing organic matrixes in dental composites, the thio-carbamate bonds also improve hydrogen bonding, and because the low Tg, flexible oligomers are swollen by the matrix, they may provide localized intermolecular reinforcement. This is especially true for thiourethane-functionalized filler particles, since it is well know that stress concentration is more marked at the filler particle-organic matrix interface, 19 as mentioned above.…”

Innovations in the Design and Application of Stimuli-Responsive Restorative Dental Polymers

“…By strategically incorporating these compounds, the network structure of the polymer can undergo controlled fragmentation and subsequent reformation, thereby allowing for stress relaxation and improved mechanical properties in the resulting polymer. Thiourethane-containing networks have also demonstrated significant potential in terms of bonds reprocessing through associative and dissociative reversible reactions [ 11 ]. Although the precise underlying reprocessable mechanism in thiourethane-containing dental polymers is not yet fully understood, it likely contributes to accelerated and enhanced stress relaxation [ 11 ].…”