Charge Transfer Complexes as Dual Thermal and Photochemical Polymerization Initiators for 3D Printing and Composites Synthesis

Abstract

The development of visible light 3D printing technology and the preparation of high-tech composites under mild conditions remain a huge challenge. This article is devoted to the development of dual thermal/photochemical initiators both for visible light 3D printing and composite preparation under mild conditions. Dual thermal and photochemical polymerization initiators are presented, a dual ability scarcely encountered in the literature. In detail, here, a series of charge transfer complexes (CTCs) that are demonstrated to be formed between phosphines (electron donors) and iodonium salt as electron acceptor are investigated as dual thermal and photochemical free radical polymerization (FRP) initiators. The CTCs exhibit excellent photo and/or thermal initiating properties for the benchmarked methacrylate resin and can be efficiently used for the curing of glass fibers or carbon fiber composites. To the best of our knowledge, this is the first access to high-tech carbon fiber composites using dual photo/thermal initiators. The formations of the CTCs were confirmed by several techniques, such as 31P NMR, UV–vis, and molecular orbital (MO) calculations. Laser write experiments at 405 nm show excellent spatial resolution performances. These systems are commercially available, stable, and environmentally friendly. Additionally, safer storage of the thermal initiators is expected (as formed in situ) compared to traditional thermal initiators (e.g., this is highly worthwhile for the replacement of peroxides). Dual approaches (photo/thermal curing) can also be used, as the same initiating system can initiate both polymerization processes, e.g., fast curing by light of the surface associated with a dark thermal curing in depth.

In silico rational design by molecular modeling of new ketones as photoinitiators in three-component photoinitiating systems: application in 3D printing

“…[4,5] Indeed, by using photopolymerization approach, a number of cross-sectional studies suggest liquid resins can be solidified on irradiated area using low-cost and safe violet light LEDs (@405nm) to produce 3D objects. [6][7][8][9][10] This approach could provide an important opportunity to advance the application on stereolithography technique or 3D printing. [11][12][13][14][15] Recently, LED-activated polymerization initiated by photoinitiators (PIs) has been investigated by a number of research groups in materials science for polymerization due to its advantages including safety, spatial control, highly efficient process in mild conditions.…”

Preparation of Iron Filler‐Based Photocomposites and Application in 3D Printing

“…[ 4 ] It remains a huge challenge to realize effective photopolymerization in the case of thick samples, fillers contained composites, or dispersed media, since the problem of insufficient light penetration is usually unable to guarantee an efficient photocuring process in depth. [ 5 ] Especially, it's of great significance to develop a reliable strategy for the access to fillers‐based composites through photopolymerization reactions.…”

Recent Advances in bis-Chalcone-Based Photoinitiators of Polymerization: From Mechanistic Investigations to Applications

“…Many approaches have been developed over the years to convert efficient photoinitiators into water-soluble structures. Moreover, such results can only be obtained after tedious and complex syntheses [211][212][213][214][215]. Conversely, the formation of charge-transfer complexes (CTCs) is an efficient strategy to easily produce numerous CTCs without requiring extensive synthetic works [216].…”