Radical formation in electron-irradiated acrylates studied by pulse radiolysis and electron paramagnetic resonance

Abstract

Electron pulse radiolysis with optical and conductometric detection as well as low‐temperature electron paramagnetic resonance (EPR) were used to study the mechanism of electron‐irradiation induced polymerisation and cross‐linking of acrylates such as triethyleneglycol (TPGDA) and butandiol (BDDA) diacrylate. Irradiation of acrylates with fast electrons generates radical cations and anions that rapidly transform to radicals. Using butyl chloride or tetrahydrofuran and water as solvents cationic and anionic pathways of radical formation were studied separately. Acrylate radical cations either deprotonate forming vinyl‐type radicals or generate covalently bonded or resonance stabilised dimer cations. Vinyl‐type radicals as well as dimer cations are able to initiate polymerisation. EPR results show that a structural transformation of TPGDA primary cations takes place by H‐transfer from the ester to the positively charged carbonyl group. Addition of solvated electrons to acrylates forms anions. Protonation of the anion at the carbonyl site leads to ketyl‐type radicals which are also able to initiate polymerisation. It is concluded that after electron‐irradiation of acrylates both cations as well as anions are important precursors of radicals which induce radical polymerisation and cross‐linking.

Synthesis and properties of UV curable polyvinylsilazane as a precursor for micro‐structuring

“…On the other hand, UV curing has distinct advantages over heat curing, through which a liquid resin quasi-instantaneously and selectively transformed into a solid polymer in the only illuminated areas. [10][11][12] It enables the easy formation of complicated microstructures with a low cost. However, there are few reports on the photocurable inorganic polymers except for polysiloxane resin with various functional groups, which kinetics was not fast enough on UV exposure.…”

“…However, the heat pulse can't be appropriate to cure the selective spatial points in the liquid phase for shaping the microstructures. On the other hand, UV curing has distinct advantages over heat curing, through which a liquid resin quasi‐instantaneously and selectively transformed into a solid polymer in the only illuminated areas . It enables the easy formation of complicated microstructures with a low cost.…”

Surface coating on cotton fabrics of new multilayer formulations based on superabsorbent hydrogels synthesized by gamma radiation designed for diapers

“…The main advantages of irradiation technology over the conventional curing of coatings by chemical methods may be attributed to the use of solvent‐free, 100% polymerizing binders with less hazard and environmental pollution, chain reaction curing initiated at low temperature. The formulation to be cured or crosslinked by irradiation usually contains unsaturated monomers (double bonds), oligomers, and other additives depending on the desired properties 2…”

“…The formulation to be cured or crosslinked by irradiation usually contains unsaturated monomers (double bonds), oligomers, and other additives depending on the desired properties. 2 UV and electron irradiation have been extensively used for curing formulations and oligomers applied by surface coatings on different surfaces for different purposes. Gamma-irradiation technology was used in combination with edible coating to produce shelfstable foods.…”

Pigment color printing on cotton and polyester fabrics with electron beam irradiation curable formulations

“…8 The formulation to be cured or crosslinked by electron beam irradiation which usually contains unsaturated mono-mers (e.g., vinyl pyrillidone, tetrahydrofurfuryl acrylate, and acrylic acid derivatives), oligomers (e.g., polyurethane acrylates, polyester acrylates, and polyether acrylates as well as epoxy acrylates), and other additives according to the desired properties. 9 Pigment printing with a formulation containing only pigment and reactive chemicals that can be cured rapidly at room temperature by electron beam or ultraviolet radiation is an attractive possibility. Primarily due to the elimination of water and solvents and the roughly 90% reduction in energy needed to evaporate them and cure the conventional binders in addition to the high production rates and smaller space requirements.…”