Photochemical, Thermal Free Radical, and Cationic Polymerizations Promoted by Charge Transfer Complexes: Simple Strategy for the Fabrication of Thick Composites

Abstract

A novel strategy for the preparation of extremely thick composites by photochemical and/or thermal free radical polymerization (FRP) and/or cationic polymerization (CP) under low-energy consumption visible light emitted diodes (LEDs) is described. The approach is based on the use of charge transfer complexes (CTCs) formed between N-aromatic amines (donors) and iodonium salts (Iod, acceptors). Remarkably, it is demonstrated for the first time that these CTCs can be used as thermal initiators for free radical polymerization (FRP) initiation with performances comparable to dibenzoyl peroxide-based systems. The decomposition temperature of these CTC thermal initiators can be modulated through the selection of the amine, providing much safer conditions for synthesis, storage, and handling than that of the classical thermal initiators. A good stability in resin is also noted.

Fenton‐Chemistry‐Mediated Radical Polymerization

“…In fact, RAFT CTAs aid in achieving control of the radical polymerization via reversible addition of the thiocarbonylthio group and rapid fragmentation reactions . Therefore, relatively analogous activation/initiation systems such as thermal, photo, enzyme, and redox based radical formation can be employed to initiate both FRP and RAFT processes. Despite the huge advances made in this field, new techniques that can overcome some of the drawbacks of these systems are continuously sought.…”

Photoinduced step‐growth polymerization of thieno[3,4‐b] thiophene derivatives. The substitution effect on the reactivity and electrochemical properties

“…Photoinduced polymerization reactions revolutionized traditional strategies and created new pathways in synthetic polymer chemistry since they are much simpler (only monomer, catalyst, and light), do not require low temperature as it is the case for all the coupling reactions, have high reaction rates, and provides spatiotemporal control. [21] Extensive research into main polymerization methods demonstrates that free-radical, [22][23][24] cationic [25][26][27][28][29][30] and anionic chain polymerizations, [31,32] and step-growth polymerizations [33][34][35] can be performed under wavelength irradiation covering UV, visible, and near-infrared (IR) region. [36][37][38][39] Recent examples of photoinduced controlled/living polymerization, [40][41][42][43][44] and ligation techniques [45] demonstrate their ability to synthesize wide range of complex macromolecules with diverse topologies, well-defined structures and desired functionalities.…”

Charge Transfer Complexes based on Various Amines as Dual Thermal and Photochemical Polymerization Initiators: A Powerful Tool for the Access to Composites

“…Recently applied CTCs based on phosphine, aniline, pyrrole, and indole acceptors were exploited as photo/thermal dual initiators but without systematic study . Some amine/Iodonium salt CTCs were also reported to initiate cationic polymerization . In this article, a series of amines will be systematically investigated to find out the impacts of the amine structure on the CTCs' initiation performance (Scheme ).…”

“…10 Recently; CTCs as a kind of efficiency, low cost in situ formed initiator has attracted much attention due to its series priorities, such as safety, spatial control, highly efficient process at room temperature (RT) and reduced emission of volatile organic compounds (VOC). [11][12][13][14][15][16][17] Most importantly, high-tech composites and 3D products can be manufactured thanks to this kind of new initiators dual photo/thermal initiating ability, which cannot be obtained by single curing method. [18][19][20][21][22][23] On one hand, high-tech composites with tack free and smooth surfaces can be easily fabricated by employing these kinds of CTCs via fast photochemical curing of the surface associated with a dark thermal curing in depth.…”

“…[24][25][26][27][28] Some amine/ Iodonium salt CTCs were also reported to initiate cationic polymerization. 13 In this article, a series of amines will be systematically investigated to find out the impacts of the amine structure on the CTCs' initiation performance (Scheme 1). The expected chemical mechanism is an electron transfer reaction between the amine (reducing agent-electron donor) and the iodonium salt (oxidizing agent-electron acceptor) that can be activated by light or by heat (possibility of dual activation).…”