Mechanistic Investigations on a Diynone Type Photoinitiator

Abstract

Recently, it has been shown that 1,5‐diphenyl‐penta‐1,4‐diyn‐3‐one (DPD) has some surprising characteristics as photoinitiator for free radical polymerization. In the present investigations we focused on the photochemistry in hydrogen donating isopropyl alcohol (IPA) and neutral acetonitrile (MeCN). HPLC and column chromatographic separation were applied for photoproduct identification. Different types of radical quenchers such as the stable radical TEMPO and the non‐polymerizable monomer methyl t‐butacrylate (t‐BAM) were also used to identify the initiating species. In IPA, fast hydrogen abstraction reaction similar to that of benzophenone was found, whereas the hydrogen donor is the initiating molecule. Significantly, slower 2 + 2 cycloaddition reaction involving the carbonyl group is the predominant pathway in MeCN. Experiments with t‐BAM indicated that DPD is directly responsible for the initiation process.magnified image

Photoinduced reverse atom transfer radical polymerization of methyl methacrylate using camphorquinone/benzhydrol system

“…The hydrogen abstraction reaction of an excited aromatic ketone in the presence of a hydrogen donor such as an amine, alcohol, ether or thiol is generally considered to be one of the best‐understood organic photochemical reactions. For example, photolysis of benzophenone in the presence of Bzh forms a pair of stable Bzh (ketyl) radicals, as a result of hydrogen atom abstraction (Scheme ) .…”

Two-Photon Polymerization of Inorganic-Organic Hybrid Polymers as Scalable Technology Using Ultra-Short Laser Pulses

“…It has to be mentioned, however, that the underlying reaction is initiated in a classical one-photon process which already gives a good measure of the reaction enthalpy, and thus of the materials' cross-linking behavior upon UV light exposure. From these measurements, two different commercially available UV initiators were chosen, henceforth labeled as Ini1 and Ini2 (BASF), respectively, as well as a specially developed photoinitiator, labeled as Ini3 (Seidl & Liska, 2007). In order to prove whether non-linear absorption and/or non-linear refraction are taking place, the magnitude of the absorption dip was determined in dependence of the excitation power.…”

Functional polymers by two-photon 3D lithography

“…Based on the outstanding performance of 1,5-diphenylpenta-1,4-diyne-3-one (DPD) [9] as a single-photon photoinitiator (PI) for radical polymerization [10], new derivatives with auxochromic groups (-OMe, -SMe, -NMe 2 , and -NPh 2 ) (see Fig. 2) were synthesized to shift the ultraviolet-visible (UV-vis) absorption into the visible range of the spectrum.…”