Directly and Indirectly Acting Photoinitiating Systems for Ring‐Opening Polymerization of ϵ‐Caprolactone

Abstract

Directly and indirectly acting photoinitiating systems for cationic ring opening polymerization (ROP) of ϵ‐caprolactone (ϵ‐CL) by using diphenyl iodonium salt (DPI) in the presence of benzyl alcohol were studied and mechanistic details were evaluated. In the direct system, the polymerization is initiated by a Brønsted acid formed upon UV irradiation of DPI. Polymerizations by indirectly acting photoinitiating systems proceeding via electron transfer reactions of photochemically formed electron donor radicals or excited states of polynuclear aromatic compounds with DPI were investigated. It was demonstrated that polymerizations proceed in a controlled manner by an activated monomer (AM) mechanism. Applicability of the photoinitiation to the other lactone monomers was validated on the example of δ‐ valerolactone (δ‐VL).

A systematic study of temperature‐dependent cationic photopolymerization of cyclic esters

“…While δVL shows first a faster polymerization than εCL, which was also observed by Yağci and co‐workers, 29 the difference is reduced at higher temperatures. The crystallinity of the resulting polymers for both monomers is very high but slightly decreases with increasing temperature, which can be related to the higher molecular weights.…”

“…GPC, NMR and STA of εCL and ⊐VL polymerized via photo-DSC with 0.5 mol% I-AL at different temperatures; conversion via NMR was calculated using the end-groups of the polymer; GPC results were obtained using a polystyrene standard polymerization progress and molecular weights were analyzed via NMR and GPC immediately after 5 min of irradiation, analogous to all other samples. While ⊐VL shows first a faster polymerization than εCL, which was also observed by Yağci and co-workers, 29 the difference is reduced at higher temperatures. The crystallinity of the resulting polymers for both monomers is very high but slightly decreases with increasing temperature, which can be related to the higher molecular weights.…”

“…The polymerization of εCL as well as δVL using not only UV light but also extending the range to visible light was recently performed by Yağci and co‐workers. In their work diphenyliodonium salts combined with benzylic alcohol and various electron‐transfer sensitizers were deployed 29 . The good compatibility of onium salts with a variety of sensitizers 30–33 creates the possibility to work with higher wavelengths and hence more environmentally friendly light sources.…”

“…In their work diphenyliodonium salts combined with benzylic alcohol and various electron-transfer sensitizers were deployed. 29 The good compatibility of onium salts with a variety of sensitizers [30][31][32][33] creates the possibility to work with higher wavelengths and hence more environmentally friendly light sources.…”

Fluorescent bioassay for SARS-CoV-2 detection using polypyrene-g-poly(ε-caprolactone) prepared by simultaneous photoinduced step-growth and ring-opening polymerizations

“…Some solutions were proposed to overcome this issue using a phosphazene base [ 12 ] or Lewis acids and acid–base organocatalytic systems [ 13 ]. We have recently introduced a new photoinduced ROP of ε-CL by using onium salts [ 14 ].…”