scholarly journals Thermal Initiators as Additives for Photopolymerization of Methacrylates upon Blue Light

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 478 ◽  
Author(s):  
Aude-Héloise Bonardi ◽  
Soraya Zahouily ◽  
Céline Dietlin ◽  
Bernadette Graff ◽  
Frédéric Dumur ◽  
...  
Keyword(s):  
Blue Light ◽  
Thermal Imaging ◽  
Light Exposure ◽  
Low Light ◽  
Absorption Properties ◽  
Visible Absorption ◽  
Mild Conditions ◽  
Esr Spin Trapping ◽  
Spin Resonance ◽  
Uv Visible

Free radical polymerization is often performed by thermal initiation but also more and more by light-assisted polymerization processes. This second approach allows the polymerization to be carried out under mild conditions (under air, upon blue light exposure, under low light intensity). The aim and the originality of the present paper is to perform photopolymerization in the presence of a thermal initiator, i.e., we can take advantage of the exothermicity of the photopolymerization process to decompose the thermal initiator, leading to enhanced polymerization rates. The performance of the photoinitiating system is discussed in the present study based on real-time Fourier-transform infrared spectroscopy measurements (following the C=C bond content evolution vs. time) and by thermal imaging experiments. Mechanisms of the new system proposed in this work are also fully detailed using cyclic voltammetry, electron spin resonance (ESR) spin trapping, and UV-visible absorption properties.

Syntheses, crystal structures and UV-visible absorption properties of five metal–organic frameworks constructed from terphenyl-2,5,2′,5′-tetracarboxylic acid and bis(imidazole) bridging ligands

2014 ◽  
Vol 43 (18) ◽  
pp. 6701-6710 ◽  
Author(s):  
Liming Fan ◽  
Xiutang Zhang ◽  
Wei Zhang ◽  
Yuanshuai Ding ◽  
Weiliu Fan ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Coordination Polymers ◽  
Metal Organic Frameworks ◽  
Tetracarboxylic Acid ◽  
Absorption Properties ◽  
Visible Absorption ◽  
Bridging Ligands ◽  
Metal Organic ◽  
Uv Visible

Five novel coordination polymers based on terphenyl-2,5,2′,5′-tetracarboxylic acid and bis(imidazole) bridging ligands.

Structures and UV-Visible Absorption Properties of Unsymmetrical Bisdithiolene Nickel Complexes

2002 ◽  
Vol 49 (5) ◽  
pp. 805-811 ◽  
Author(s):  
Chih-Chieh Wang ◽  
Wei-Ching Wu ◽  
Gene-Hsiang Lee ◽  
Chin-Ti Chen
Keyword(s):  
Nickel Complexes ◽  
Absorption Properties ◽  
Visible Absorption ◽  
Uv Visible

N-Picrylethylenediamine – methoxide ion interactions: N-deprotonation and σ-complex formation reactions

1981 ◽  
Vol 59 (5) ◽  
pp. 795-801 ◽  
Author(s):  
Erwin Buncel ◽  
Masashi Hamaguchi ◽  
Albert R. Norris
Keyword(s):  
Carbon Atom ◽  
Dimethyl Sulfoxide ◽  
Solvent Mixtures ◽  
Absorption Properties ◽  
Visible Absorption ◽  
Ring Carbon ◽  
Ion Interactions ◽  
Uv Visible ◽  
Methoxide Ion ◽  
Ring Carbon Atom

The interactions of N-picrylethylenediamine as the HCl salt (PED) with methoxide ion in dimethyl sulfoxide – methanol (DMSO/MeOH) media and with 1,4-diazabicyclooctane in dimethyl sulfoxide have been investigated spectrophotometrically at 25.0 °C. Evidence is presented to show that, in solvent mixtures rich in dimethyl sulfoxide (e.g. 95/5, V/V, DMSO/MeOH), deprotonation reactions at the nitrogen centres on the ethylenediamine occur in preference to reactions in which σ-complexes are formed via addition of CH3O− to one or more ring carbon atoms. The initial 1:1 interaction of CH3O− and PED results in the rapid, reversible deprotonation of the NH centre while the 2:1 interaction is associated with rapid, reversible abstraction of H+ from the NH3+ centre. At mole ratios of CH3O− to PED > 3 a σ-complex is formed as a result of the addition of CH3O− ion to a C-3 ring carbon atom of the di-deprotonated PED. The uv–visible absorption properties of these various species are reported and compared to the properties of corresponding species formed in related systems.

Nighttime Blue Light Exposure and Breast Cancer

2021 ◽  
pp. 30-33
Author(s):  
David Jaynes ◽  
Paul Switzer
Keyword(s):  
Breast Cancer ◽  
Risk Factor ◽  
Blue Light ◽  
Shift Work ◽  
Light Exposure ◽  
Night Shift ◽  
Background Information ◽  
Common Disease ◽  
Essential Information ◽  
Night Shift Work

The purpose of this article is to provide background information and the current understanding of a less familiar cause of female breast cancer; exposure to ultraviolet light at night. Breast cancer is a common disease that causes significant morbidity and mortality in women. There are several risk factors for breast cancer, most of which are genetic and environmental in nature. An often-overlooked risk factor is exposure to blue light during night shift work, which decreases melatonin production. One of the many cancer-preventing properties of melatonin is to limit estrogen production. Increased lifetime exposure to estrogen is a well-known cause of breast cancer. Awareness of nighttime blue light exposure as a breast cancer risk factor by women doing night shift work and those exposed to nighttime light via smartphones and laptops, is essential information to know so that protective measures can be taken.

Effects of pre-bedtime blue-light exposure on ratio of deep sleep in healthy young men

2021 ◽  
Author(s):  
Masao Ishizawa ◽  
Takuya Uchiumi ◽  
Miki Takahata ◽  
Michiyasu Yamaki ◽  
Toshiaki Sato
Keyword(s):  
Blue Light ◽  
Light Exposure ◽  
Young Men ◽  
Deep Sleep

Remarkable kinetic stability of α-thiocarbamoyl substituted 4-methoxybenzylcations

1998 ◽  
Vol 76 (12) ◽  
pp. 1910-1915 ◽  
Author(s):  
Robert A McClelland ◽  
Victoria E Licence ◽  
John P Richard ◽  
Kathleen B Williams ◽  
Shrong-Shi Lin
Keyword(s):  
Key Words ◽  
Strong Interaction ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Visible Absorption ◽  
Methyl Group ◽  
Thioamide Group ◽  
Azide Ion ◽  
Uv Visible ◽  
Leaving Groups

4-Methoxybenzyl cations bearing α-(N,N-dimethylcarbamoyl) and α-(N,N-dimethylthiocarbamoyl) substituents have been generated photochemically upon irradiation of precursors with pentafluorobenzoate or 4-methoxybenzoate leaving groups. The ions have been observed with flash photolysis in 40:60 acetonitrile:water and in 50:50 methanol:water, and rate constants were measured for their decay in solvent alone and for their capture by azide ion. The cations so studied and their lifetimes in 40% acetonitrile are 6, ArC+H-CONMe2, 0.6 μs; 2, ArC+H-CSNMe2, 7 ms; and 4, ArC+(CH3)-CSMe2, 6 ms, where Ar = 4-MeOC6H4. The cation 4 reacts with solvent by elimination of a proton from the α-methyl group, and the rate constant for solvent addition must be less than 1 s-1. The CSNMe2 substituted cations are 105-107-fold longer lived than analogs where the thioamide group has been replaced with an α-methyl. The UV-visible absorption spectra of these two cations also show significant differences from those of typical 4-methoxybenzyl cations. Thus, both the lifetimes and spectra point to a strong interaction of the benzylic centre with the thioamide group. Key words: flash photolysis, thiocarbamoyl stabilized carbocation, photosolvolysis.

Sign in / Sign up

Export Citation Format

Share Document