Naphthalimide Aryl Sulfide Derivative Norrish Type I Photoinitiators with Excellent Stability to Sunlight under Near-UV LED

Abstract

A series of Norrish type I photoinitiators (NASs), which are naphthalimide aryl sulfide derivatives, are prepared. The potential mechanism involved in the photolysis of NASs under UV LED at 405 nm is investigated by steady-state photolysis, nuclear magnetic resonance, electron spin resonance, fluorescence spectroscopy, cyclic voltammetry, and laser flash photolysis and by calculating the bond dissociation energies of the C–S bonds of NASs. The as-prepared photoinitiators NAS5 and NAS6 can efficiently initiate free radical photopolymerization of (methyl)­acrylate monomers under UV LED exposure at 405 nm. NASs/iodonium salt systems can initiate the cationic photopolymerization of epoxide. Interestingly, NASs exhibit an excellent stability to sunlight. Thus, the use of NASs makes the preparation, storage, and application of photocurable formulations convenient.

Cleavable Unimolecular Photoinitiators Based on Oxime‐Ester Chemistry for Two‐Photon Three‐Dimensional Printing

“…Photoinduced direct cleavage is another more efficient mechanism for generating active free radicals . Such a mechanism has been used to produce Norrish Type I photoinitiators in traditional UV curing.…”

Novel ketone derivative-based photoinitiating systems for free radical polymerization under mild conditions and 3D printing

“…And usually, the photopolymerization reaction can be initiated by the type I (mono-component initiating system) or type II (bi-component or multiple-component initiating system) photoinitiators, of which the latter is especially versatile. [1][2][3][4][5] Thanks to these intrinsic advantages, such as fast polymerization kinetics, mild reaction conditions, environmentally friendly polymerization process, its economic aspect with less energy consumed, as well as an excellent spatial and temporal control, photopolymerization reactions have been widely studied and developed over the past decades. Now, the photopolymerization technique is attracting a widespread attention in both traditional and high-tech areas, including coatings, paints, inks, adhesives, microlithography, microelectronics, dentistry, and photocuring 3D-printing…to name just a few.…”

Effect of ketyl radical on the structure and performance of holographic polymer/liquid-crystal composites

“…The fast gelation process in the constructive regions allows for a rapid holographic patterning while the prolonged gelation in the destructive regions provides longer time for the phase separation [12][13][14]. Nevertheless, despite the amazing progress on the elegant design of new photo-mediated systems [26][27][28][29][30][31][32][33][34][35][36] for a myriad of attractive applications such as sequential polymerization control [29], 3D printing [30], surface grafting [31], and fabricating conductive composites [36], very few efforts have been made to implement such a spatiotemporal control during holography [13]. Peng and co-workers [12,13] disclosed that a "photoinitibitor" with concurrent initiation and inhibition functions was able to exert a precise control over the photopolymerization kinetics and gelation during holographic patterning.…”