Mechanisms of photochemical reactions in solution. LVIII. Photoreduction of camphorquinone

Monroe, Bruce M.; Weiner, Steven A.

doi:10.1021/ja01030a041

Cited by 69 publications

(25 citation statements)

References 6 publications

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“…CQ undergoes photoreduction in solvents containing readily abstractable hydrogens like methanol [43][44][45] , isopropyl alcohol 43-44, 46, 47) and o-and p-xylene 48) . No transformation is observed in benzene or carbon tetrachloride 45) .…”

Section: Resultsmentioning

confidence: 99%

“…Further ketyl radicals disappear by a disproportionation reaction rather than a coupling, producing a mixture of structurally different endo-hydroxy camphors 43,46) . Additionally a variety of oxidation (camphoric anhydride) and reduction (mixture of acyloins) products is formed in the presence of air 45) .…”

Section: Resultsmentioning

confidence: 99%

“…Additionally a variety of oxidation (camphoric anhydride) and reduction (mixture of acyloins) products is formed in the presence of air 45) . The CQH9 radical has been detected by ESR studies of irradiated solutions of CQ in isopropyl alcohol and p-xylene 43,49) . The photoreduction of CQ alone and in the presence of different hydrogen atom donors in a methanol solution in the presence of air is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Effect of peroxides and hydroperoxides on the camphorquinone-initiated photopolymerization

Nie

Andrzejewska

Rabek³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: This work describes the camphorquinone (CQ)-initiated photopolymerization of tri(ethylene glycol) dimethacrylate in the presence of (hydro)peroxides. On the basis of the kinetics of the polymerization in the presence of model compounds, the effect of hydroperoxides and peroxides has been examined. Generally, an addition of low molecular peroxides such as tert-butyl peroxide and dicumyl peroxide increases the rate of polymerization (R p ) in both air and nitrogen, whereas an addition of low molecular hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxide decreases R p . However, hydroperoxides present in low concentrations increase R p in nitrogen. A mechanism for these reactions is suggested.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Effect of peroxides and hydroperoxides on the camphorquinone-initiated photopolymerization

Nie

Andrzejewska

Rabek³

et al. 1999

Macromol. Chem. Phys.

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“…Titely et al 9) stated in their study that the reduction in bond strength might be related to the presence of residual hydrogen peroxide which interfered with resin attachment and inhibited resin polymerization at or near the enamel surface and they showed that the immersion of hydrogen peroxide treated teeth in water could leach out the hydrogen peroxide and restore bond strength values. Since dental adhesives polymerize by a free radical polymerization mechanism that involves the generation of free radicals through light-activated redox initiators, 18) the hydrogen peroxide may break down to release oxygen that is trapped within the adhesive during light-activation. The released oxygen from the bleached enamel probably results in incomplete polymerization of the adhesive in these regions 10,19) .…”

Section: ⅳ Discussionmentioning

confidence: 99%

The effect of various commercially available bleaching agents on the microshear bond strength of composite resin to enamel

Chang

Cho

Kim

2004

J Korean Acad Conserv Dent

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This study evaluated the microshear bond strength of composte resin to teeth bleached with commercial whitening strips and compared with those bleached with home bleaching gel. Twelve extracted human central incisors were cut into pieces and central four segments were chosen from each tooth and embedded in acrylic resin. Four blocks with 12 tooth segments embedded in acrylic resin were acquired and numbered from group one to group four. Group 1 was bleached with Crest Whitestrips, group 2 with Claren, group 3 with Opalescence tooth whitening gel (10% carbamide peroxide). Group 4 was used as control. The bleaching procedure was conducted for 14 days according to the manufacturer' s instructions; the bleaching strips twice a day for 30 min and the bleaching gel once a day for 2 hr. After bleaching, composite resin (Filtek Supreme) was bonded to the enamel surfaces with a self-etching adhesive (Adper Prompt L-Pop) using Tygon tube. Microshear bond strength was tested with a universal testing machine (EZ-test). The data were statistically analysed by one-way ANOVA. The study resulted in no statistical differences in microshear bond strength between the tooth segments bleached with 2 different whitening strips and bleaching gel. It can be concluded that the effect of bleaching with either commercial whitening strips or bleaching gel on enamel is minimal in bonding with self-etching adhesive to composite resin. [J Kor Acad Cons Dent 29(3):219-225, 2004]

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“…An important issue in visible light-curing (VLC) composites development and research as well as in photo-chemistry in general is the question: How fast do composites cure, and how deep are they properly cured [1][2][3][4][5][6]? Since the development of VLC dental restoratives numerous studies have investigated the curing kinetics [7][8][9][10][11], the degree of cure (DC) [11][12][13][14] and the depth of cure (DC) [14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Dielectric analysis of depth dependent curing behavior of dental resin composites

et al. 2014

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Objectives. The aim of this study is to investigate depth dependent changes of polymerization process and kinetics of visible light-curing (VLC) dental composites in real-time. The measured quantity -"ion viscosity" determined by dielectric analysis (DEA) -provides the depth dependent reaction rate which is correlated to the light intensity available in the corresponding depths derived from light transmission measurements. Methods. The ion viscosity curves of two composites (VOCO Arabesk Top and Grandio) were determined during irradiation of 40 s with a light-curing unit (LCU) in specimen depths of 0.5/0.75/1.0/1.25/1.5/1.75 and 2.0 mm using a dielectric cure analyzer (NETZSCH DEA 231 with Mini IDEX sensors). The thickness dependent light transmission was measured by irradiation composite specimens of various thicknesses on top of a radiometer setup. Results. The shape of the ion viscosity curves depends strongly on the specimen thickness above the sensor. All curves exhibit a range of linear time dependency of the ion viscosity after a certain initiation time. The determined initiation times, the slopes of the linear part of the curves, and the ion viscosities at the end of the irradiation differ significantly with depth within the specimen. The slopes of the ion viscosity curves as well as the light intensity values decrease with depth and fit to the Lambert-Beer law. The corresponding attenuation coefficients are determined for Arabesk Top OA2 to 1.39 mm -1 and 1.48 mm -1 , respectively, and for Grandio OA2 with 1.17 and 1.39 mm -1 , respectively. For thicknesses exceeding 1.5 mm a change in polymerization behavior is observed as the ion viscosity increases subsequent to the linear range indicating some kind of reaction acceleration. Significance. The two VLC composites and different specimen thicknesses discriminate significantly in their ion viscosity evolution allowing for a precise characterization of the curing process even with respect to the polymerization mechanism.

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Mechanisms of photochemical reactions in solution. LVIII. Photoreduction of camphorquinone

Cited by 69 publications

References 6 publications

Effect of peroxides and hydroperoxides on the camphorquinone-initiated photopolymerization

Effect of peroxides and hydroperoxides on the camphorquinone-initiated photopolymerization

The effect of various commercially available bleaching agents on the microshear bond strength of composite resin to enamel

Dielectric analysis of depth dependent curing behavior of dental resin composites

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