A low migration phosphine to overcome the oxygen inhibition in new high performance photoinitiating systems for photocurable dental type resins

Abstract

The objective of this work was to propose a novel low migration additive (i.e. a phosphine) to overcome the oxygen inhibition in a camphorquinone (CQ) base photoinitiating system for the polymerization of methacrylates (e.g. a bisphenol A‐glycidyl methacrylate (Bis‐GMA)/triethyleneglycol dimethacrylate (TEGDMA) blend (70%/30% w/w)) upon exposure to a commercial blue light emitting diode centred at 477 nm. CQ/amine/phosphine derivative or CQ/amine/iodonium salt/phosphine derivative combinations were studied. Real‐time Fourier transform IR and photo‐DSC experiments were used to monitor the polymerization profiles. Remarkably, it was found that the addition of the new phosphine derivative to CQ/amine or CQ/amine/iodonium salt noticeably improved the rate of polymerization and the final conversion in air. A low migration was found for this additive as shown by HPLC experiments in agreement with a copolymerizable behaviour. No additional yellowing of the film was observed. Electron spin resonance spectrometry was used to detect the produced radicals. The overall chemical mechanisms are investigated and discussed. © 2016 Society of Chemical Industry

2‐Oxo‐2(tert‐butyldimethylsilyl)Acetic Acid (DKSi‐COOH) as a New Water‐Soluble Visible Light Type I Photoinitiator for Free Radical Polymerization

“…[8] The most commonly used PIS is based on camphorquinone (CQ) and an amine, for example, a tertiary aromatic amine as co-initiator. [3,[8][9][10][11][12] Nevertheless, some aromatic amines can present inherent toxicity issues [13,14] so that the development of amine-free PISs Compared to DKSi, the replacement of the ester function by a carboxylic acid function (DKSi-COOH) does not affect the absorption band but leads to slightly lower molar extinction coefficients. Nevertheless, DKSi-COOH exhibits interesting absorption properties for blue light and particularly in acidic conditions due to the presence of the carboxylic acid moiety.…”

New 1,8-Naphthalimide Derivatives as Photoinitiators for Free-Radical Polymerization Upon Visible Light

“…However, these radicals capable of reacting with a compound, such as a phosphine, to generate RO• radical were less stable and, therefore, were able to initiate free-radical polymerization. The role of phosphine as an oxygen scavenger has been already reported in the literature in [28]. The mechanism is illustrated in Scheme 6.…”

A New Phosphine for Efficient Free Radical Polymerization under Air

“…Phosphines have been already reported in the literature as efficient additives to reduce/overcome the inhibition of the polymerization process caused by the ambient oxygen. Indeed, phosphines can convert stable peroxyl radicals (ROO • ) which are inefficient in the polymerization initiation process to new initiating radicals (RO • ) according to the following reactions: [ 1–5 ] …”

“…For the new phosphine presented here (with a sulfonate substituent), the same mechanism can be expected (r1 and r2) as observed for other triarylphosphines in ref. [5]. The polymerization under air of composites is a huge challenge and the development of photoinitiating systems able to work in such mild conditions (visible light, aerated conditions) is highly desired.…”

“…The procedure to follow photopolymerization processes by real‐time Fourier transform infrared spectroscopy (FTIR) has been described in detail in refs. [5,10]…”