A study of the photodecomposition products of an acylphosphine oxide and 2,2-dimethoxy-2-phenylacetophenone

Baxter, Jane E.; Davidson, R. S.; Hageman, Hendrik J.; Hakvoort, G.; Overeem, Ton

doi:10.1016/0032-3861(88)90264-9

Cited by 27 publications

(17 citation statements)

References 7 publications

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“…3A-C) or HAp content (Fig. 3D) is consistent with the notions that TPO's photoinitiation is not interfered by 4E (Baxter et al 1988) or pH . These 2 characteristics are the reasons we chose TPO as the photoinitiator as opposed to the widely used 2-component and 3-component systems based on camphorquinone (CQ), amine, and optional iodonium salt.…”

Section: Discussionsupporting

confidence: 88%

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

et al. 2015

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Light cure is a popular mode of curing for dental adhesives. However, it suffers from inadequate light delivery when the restoration site is less accessible, in which case a self-cure mechanism is desirable to salvage any compromised polymerization. We previously reported a novel self-cure system mediated by ethyl 4-(dimethylamino)-benzoate (4E) and hydroxyapatite (HAp). The present work aims to investigate if such self-cure phenomenon takes place in adhesives that underwent prior inadequate light cure and to elucidate if HAp released from the dental etching process is sufficient to trigger it. Model self-etch adhesives were formulated with various components, including bis[2-methacryloyloxy)ethyl]-phosphate (2MP) as acidic monomer and trimethylbenzoyl-diphenylphosphine oxide (TPO) as photoinitiator. In vitro evolution of degree of conversion (DC) of HAp-incorporated adhesives was monitored by infrared spectroscopy during light irradiation and dark storage. Selected adhesives were allowed to etch and extract HAp from enamel, light-cured in situ, and stored in the dark, after which Raman line mapping was used to obtain spatially resolved DC across the enamel-resin interface. Results showed that TPO+4E adhesives reached DC similar to TPO-only counterparts upon completion of light irradiation but underwent another round of initiation that boosted DC to ~100% regardless of HAp level or prior light exposure. When applied to enamel, TPOonly adhesives had ~80% DC in resin, which gradually descended to ~50% in enamel, whereas TPO+4E adhesives consistently scored ~80% DC across the enamel-resin interface. These observations suggest that polymerization of adhesives that underwent insufficient light cure is salvaged by the novel self-cure mechanism, and such salvaging effect can be triggered by HAp released from dental substrate during the etching process.

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Section: Discussionsupporting

confidence: 88%

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

et al. 2015

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“…For high intensity irradiation methyl benzoate was virtually the only product of R 1 , which indicates nearly quantitative photo-fragmentation. Thus, the contradictory results on photolysis products of DMPA reported by Sandner and Osborn 19 and Davidson et al 20 are attributed to a strong influence of the light intensity and excitation wavelength employed on the photochemical fragmentation of DMPA. Trends presented in Figure 4 show that the photolysis of DMPA in methacrylate monomers results in an increase in absorbance associated to the presence of photoproducts which absorb in the same wavelength region as DMPA.…”

Section: Resultsmentioning

confidence: 94%

“…They found methyl benzoate (45-61% yield), benzaldehyde (17-20%), benzil (7-11%), and acetophenone (2-8%). On the other hand, Davidson et al 20 reported the products of decomposition of DMPA in dinonyl phthalate under aerobic conditions. Besides methyl benzoate they found methyl anisolate, methyl o-and p-benzoylbenzoate and benzoic acid as major components, and benzaldehyde, benzophenone, benzil, acetophenone, and biphenyl in minute amounts.…”

Section: Resultsmentioning

confidence: 98%

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Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Mucci

Vallo

2011

J of Applied Polymer Sci

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The efficiency of 2,2-Dimethoxy-2-phenylacetophenone (DMPA) for the photopolymerization of methacrylate monomers in thick sections was assessed. DMPA is an efficient photoinitiator for thick sections (%2 mm) because a fast reaction and high conversions are obtained with concentrations as low as 0.25 wt % DMPA. The polymerization rate increased when the DMPA content increased from 0.125 wt % to 0.25 wt %. However, the conversion versus irradiation time profiles in resins containing 0.25 wt % or 0.5 wt % DMPA were similar. This is attributed to the screening effect caused by excessive levels of DMPA. In addition, the consumption of DMPA under UV irradiation was accompanied by the appearance of light absorbing photoproducts. Because the absorbing species nearest to the light source absorb part of it, the light fails to reach the deeper layers of the sample. The overall effect of light screening is a reduced photoinitiation rate and double bond conversion along the irradiation path. This effect was compensated by the use of irradiation sources of higher intensity; which increased the initiation rate by increasing the production of primary radicals. DMPA is colorless and it does not require the presence of amine as coinitiator. These properties make DMPA attractive as photoinitiator of dental composites.

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“…The photolysis of both compounds leads to C(O)-P bond cleavage from a triplet state [23,24]. The main reactions are outlined in Fig.…”

Section: Resultsmentioning

confidence: 99%

Electron-nuclear spin transitions in free phosphonyl radicals detected via CIDNP

et al. 2004

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Electron-nuclear spin transitions in short-lived phosphonyl radicals have been investigated experimentally by nuclear magnetic resonance detection of nuclear polarization in diamagnetic reaction products in low magnetic fields (15-80 mT) for 3~p-centered radicals formed in laser photolysis of (2,4,6-t¡ oxide and 2,4,£ acid dimethyl ester. A theoretical model on the basis of the numerical sotution of the kinetic equation for the density matrix of a radical with one nonzero hyperfine coupling constant has been employed to study the main peculiarities of this effect and to account for the data quantitatively.

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A study of the photodecomposition products of an acylphosphine oxide and 2,2-dimethoxy-2-phenylacetophenone

Cited by 27 publications

References 7 publications

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Electron-nuclear spin transitions in free phosphonyl radicals detected via CIDNP

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