Acyl-1,4-Dihydropyridines as Efficient Dual-Mode Photoinitiators for Radical Polymerisation under Blue and Green Light
Year: 2026
Type: preprint
Abstract: Acyl-1,4-dihydropyridines are readily accessible radical precursors, but their poten al as photoini ators has remained largely unexplored.Here we show that these easily prepared compounds are dual-mode photoini ators that operate across the visible spectrum.Under blue light (405-475 nm), they act directly as Type I photoini ators: photoinduced fragmenta on releases acyl radicals that polymerise acrylate and methacrylate monomers.In trimethylolpropane triacrylate, DHP-2-NMe₂ and DHP-5-OMe show the highest Type I ac vity, with DHP-2-NMe₂ inducing gela on in only 6 s at a loading of 0.042 wt%.Under green light (525 nm), the DHPs serve as co-ini ators in photosensi sed Type II systems.With porphyrin-, BODIPY-and xanthene-based photosensi sers, rapid photopolymerisa on is observed; DHP-5-OMe is the most consistent co-ini ator, and PdOEP gives gela on mes of 2-14 s (median 3 s).Subs tuent-dependent reac vity observed in radical-trapping experiments supports a photoinduced electron-transfer pathway that, under op mised condi ons, delivers a Giese-type adduct in 92% yield under green light.Finally, combining DHP-1-H with I2BDP in a photopolymerisable glass increases the holographic diffrac on efficiency at 532 nm from 43% to 82% and the refrac ve-index modula on from 1.43 × 10⁻³ to 2.39 × 10⁻³.Single-step synthesis, strong visible-light absorp on and complete photobleaching make acyl-DHPs a prac cal pla orm for visible-light photopolymerisa on and holographic pa erning.
Source: ChemRxiv
Institutions: Technological University Dublin, University College Dublin
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Funder: Research Ireland
Awards: G3214794694, G7424277081
OpenAlex ID: W7215034850