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.
Photoinduced thermal polymerization upon Near‐InfraRed (NIR) light has been recently reported in the literature as an efficient tool for polymer synthesis. In this work, a completely different approach is developed since polymeric materials containing a very low amount of a stimuli‐responsive compound are prepared by using a benchmark UV photoinitiator. As the stimuli‐responsive compound, an organic dye strongly absorbing in the near‐infrared region is selected. The heat released by its irradiation with an inexpensive and highly penetrating NIR light source allows the development of an unprecedented approach for reprocessing, reshaping, recycling, and self‐healing. Several parameters have been studied in order to determine their influence on the polymer temperature: the wavelength of the NIR irradiation, the irradiance of the NIR light source, the choice of heater (IR‐813 p‐toluenesulfonate or a squaraine dye), and the heater concentration. The thermoplastics bonding and debonding has also been studied and showed promising results since two pieces of polymers could be pasted together after a short time of NIR irradiation. Finally, self‐healing ability of the thermoplastic is investigated and furnished impressive results even for large scratches.
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