The Dye-sensitized Photopolymerization of Vinyl Acetate in the Presence of Benzoyl Peroxide

Takakura, K.; Takayama, Gozo

doi:10.1246/bcsj.38.328

Cited by 5 publications

(1 citation statement)

References 3 publications

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“…Control experiments (Tables S1 and S2) performed in the darkness for 24 h suggest that activation of dark polymerization is only possible in the presence of a brief initial irradiation period. Although Pemberton and Johnson, , Yang and Oster, Smets, Delzenne, and Toppets, Tigulla and Vuruputuri, Takura and Takayama, and others − had proposed a similar free radical polymerization system with ascorbic acid, these mechanisms disagreed upon two key issues: the role of the reduced dyes and the importance of oxygen.…”

Section: Resultsmentioning

confidence: 99%

Photoinduced Oxygen Reduction for Dark Polymerization

Shanmugam

Boyer

2017

Macromolecules

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Photopolymerization systems for controlled/living radical polymerization (CLRP) have often been dependent on continuous irradiation to sustain radical production. Although this approach offers an opportunity to impose spatial and temporal control, it remains an energy inefficient process. As energy storage for CLRP remains an unexplored area in polymer chemistry, it may provide an opportunity for designing energy efficient polymerization. In this contribution, we propose a novel energy storage system where in situ production of hydrogen peroxide from molecular oxygen was achieved after a brief period of visible light irradiation in the presence of photo-organocatalyst and ascorbic acid. Upon ceasing irradiation, the slow generation of hydroxyl radicals from hydrogen peroxide in the presence of ascorbic acid allows for continuous radical generation in the dark. The highlight of this system stems from the fact that irradiation as brief as 5 min allows storage of enough energy as hydrogen peroxide to perform continuous polymerization to reach high monomer conversions in the dark. In addition, these aqueous polymerizations do not require nitrogen purging as oxygen is required for the production of hydrogen peroxide which becomes the radical source that initiates the polymerization. Interestingly, the amount of oxygen present in the reaction mixture affects the rate of polymerization. The system was found to be robust and versatile as it is able to accommodate different monomer families (acrylate, acrylamide, and methacrylate) and RAFT agents (dithiobenzoates and trithiocarbonates). Finally, this approach can help to solve one of the major limitations of photopolymerization pertaining to light penetration.

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Section: Resultsmentioning

confidence: 99%

Photoinduced Oxygen Reduction for Dark Polymerization

Shanmugam

Boyer

2017

Macromolecules

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Photopolymerization studies: I. Polymers from new photoredox catalyst system

Rust

Miller

Margerum

1969

Polymer Engineering & Sci

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A new photoredox catalyst is described wherein a phenothiazine dye in its excited state oxidizes a catalyst to a free radical. This free radical efficiently initiates the polymerization of metal acrylates giving rise to polymers which are insoluble in the monomer-containing medium. The polymers precipitate as insoluble colloidal particles. Optical transmission measurements are used to follow the polymerization and to calculate the number and size of the polymer particles. The effect of various factors such as the nature of the catalyst and the photooxidant, the pH and the temperature of the medium on photopolymerization are described. It is indicated that this new system may be useful for rapid photographic imaging and display applications.Dye-sensitized photopolymerization of acrylic and vinyl monomers has been studied by many investigators (1-22). It has been suggested that the use of visible radiation in photochemical sequences leading to polymerization required the presence of an electron donor and oxygen (2, 15, 23-26). Most investigators have not recognized the importance of direct photochemical generation of the free-radical initiator. Usually, studies have centered around initiator systems which required multiple reactions or whose free radicals were very inefficient for initiating polymerization.Dyes of certain classes, in particular, the phenothiazine dyes, are strong oxidants in their photoexcited state (probably the triplet state). Redox catalyst initiation of polymerization (27) has been shown to be a very efficient means of polymerizing vinyl and acrylic monomers. Photochemically induced redox catalysis, referred to here as "photoredox catalysis," has proved useful to initiate polymerization directly, and with efficiencies which are greater than any heretofore reported for dye-sensitized photopolymerization. The present paper deals with a photoredox catalyst system consisting of a phenothiazine dye photooxidant, such as methylene blue and thionine, and an organic sulfinic compound, such as p-toluenesulfinic acid. The system does not require oxygen to function efficiently, but on the other hand, it is not particularly adversely affected by the presence of oxygen. Organic sulfinic acids, particularly when activated by aromatic amines, have been proposed and studied for initiating the polymerization of vinyl and acrylic monomers (28, 29). The system described in this paper, along with results presented in other papers of this series ( l ) , has led to dry-processed photographic techniques and information storage and retrieval systems. EXPERIMENTAL MATERIALS AND METHODSBarium diacrylate was prepared by neutralizing distilled acrylic acid with a distilled water solution of barium hydroxide octahydrate. The pH was usually adjusted to 5.0 to 7.0 with excess acrylic acid and the solution filtered. In some preparations the solution was concentrated under vacuum, and in other preparations undistilled acrylic acid was used, followed by treatment with activated carbon and filtration. Generally, the concentratio...

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Polymerization of vinyl acetate using visible radiation and a dye-reducing agent sensitizer: 1. Pre-initiation and initiation reactions involving ethyl eosin and ascorbic acid

Pemberton

Johnson

1984

Polymer

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The Dye-sensitized Photopolymerization of Vinyl Acetate in the Presence of Benzoyl Peroxide

Cited by 5 publications

References 3 publications

Photoinduced Oxygen Reduction for Dark Polymerization

Photoinduced Oxygen Reduction for Dark Polymerization

Photopolymerization studies: I. Polymers from new photoredox catalyst system

Polymerization of vinyl acetate using visible radiation and a dye-reducing agent sensitizer: 1. Pre-initiation and initiation reactions involving ethyl eosin and ascorbic acid

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