Photoinitiator

In chemistry, a photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible).

Some small molecules in the atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog).

[1] Nitrogen dioxide can also be photolytically cleaved by photons of wavelength less than 400 nm[2] producing atomic oxygen and nitric oxide.

Benzoyl peroxide, much like azobisisobutyronitrile, is a white powder used as a photoinitiator in various commercial and industrial processes, including plastics production.

Unlike AIBN, however, benzoyl peroxide produces oxygen gas upon decomposing, giving this compound a host of medical uses as well.

The physical properties of the cured resins are affected by the generation of primary radicals during the initial stage of polymerization.

[7] When exposed to light it forms four radicals (2, 3, 5) per decomposed molecule (1), making it highly efficient in initiating polymerization.

Large format sheets with a thin photopolymer coating cured with a UV lamp.
Hydrogen peroxide, the simplest peroxide
Nitrogen dioxide, a large contributor to the production of smog
Azobisisobutyronitrile, a commonly used industrial photoinitiator, and its breakdown into two radicals and nitrogen gas
Benzoyl peroxide, a common photoinitiator used in plastics production and in acne medication
example of acrylate polymerization via radical photoinitiation. This type of hydrogel is sometimes used for biosensors as the conditions used are relatively mind to protein allowing them to be entrapped in the hydrogel, whilst retaining functionality and are porous enough to allow the diffusion of small molecules.[6]
example of acrylate polymerization via radical photoinitiation. This type of hydrogel is sometimes used for biosensors as the conditions used are relatively mind to protein allowing them to be entrapped in the hydrogel, whilst retaining functionality and are porous enough to allow the diffusion of small molecules . [ 6 ]
Mechanism of Irgacure 819 to form 4 radicals.