Initiators Based on Benzaldoximes: Bimolecular and Covalently Bound Systems

Abstract

Typical bimolecular photoinitiators (PIs) for radical polymerization of acrylates show only poor photoreactivity because of the undesired effect of back electron transfer. To overcome this limitation, PIs consisting of a benzaldoxime ester and various sensitizers based on aromatic ketones were introduced. The core of the photoinduced reactivity was established by laser flash photolysis, photo-CIDNP, and EPR experiments at short time scales. According to these results, the primarily formed iminyl radicals are not particularly active. The polymerization is predominantly initiated by C-centered radicals. Photo-DSC experiments show reactivities comparable to that of classical monomolecular type I PIs like Darocur 1173.

Styryl silsesquioxane photoresist

“…Two factors are key in selecting a proper photoinitiator for the styryl SSQ photoresist. One is the effective generation of active radical species, and the other is an absence of structures that can interact with SSQs. 1‐[9‐Ethyl‐6‐(2‐methylbenzoyl)‐9H‐carbazol‐3‐yl] ethanone‐1‐(O‐acetyloxime) ( 2 ) is said to generate a reactive methyl radical.…”

Synthesis and Structure-Activity Relationship of <i>N</i>-Substituted Carbazole Oxime Ester Photoinitiators

“…An oxime ester photoinitiator is a high-efficiency type I photoinitiator, which can undergo N-O bond decomposition under irradiation to generate imine free radicals and acyloxy free radicals. The latter decarboxylates to produce active species and initiates the polymerization of acrylate monomers [15,16].…”

NIR‐Sensitized Activated Photoreaction between Cyanines and Oxime Esters: Free‐Radical Photopolymerization

“…As a result, more research activities resulted in the commercialized oxime esters OXE‐01 and OXE‐02 (see Figure ) . Photophysical investigations and time‐resolved spectroscopy helped to direct the development of such materials …”

“…[3][4][5][6] Photophysical investigations and time-resolved spectroscopy helped to direct the development of such materials. [7,8] Recently,o xime esters comprising ac oumarin structure, exhibiting as ignificant red bathochromic shift of absorption, enabled their use in combination with industrial UV-Blue LED devices. [9] This finding has received attention since new regulations require the use of such light sources in new green and energy saving technologies.…”