Thermal Initiators as Additives for Photopolymerization of Methacrylates upon Blue Light

Abstract

Free radical polymerization is often performed by thermal initiation but also more and more by light-assisted polymerization processes. This second approach allows the polymerization to be carried out under mild conditions (under air, upon blue light exposure, under low light intensity). The aim and the originality of the present paper is to perform photopolymerization in the presence of a thermal initiator, i.e., we can take advantage of the exothermicity of the photopolymerization process to decompose the thermal initiator, leading to enhanced polymerization rates. The performance of the photoinitiating system is discussed in the present study based on real-time Fourier-transform infrared spectroscopy measurements (following the C=C bond content evolution vs. time) and by thermal imaging experiments. Mechanisms of the new system proposed in this work are also fully detailed using cyclic voltammetry, electron spin resonance (ESR) spin trapping, and UV-visible absorption properties.

Recent advances on perylene-based photoinitiators of polymerization

“…[26] Considering that the development of visible light photoinitiating systems activable under low light intensity and in the visible range is extremely recent, this research is still in a prospective phase, at the search of innovative structures that could act as visible light photoinitiators of polymerization. In the course of the different investigations, a wide range of structures have been examined and naphthalimides, [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] porphyrins, [42,43] chromones and flavones, [44][45][46][47][48] acridones, [49,50] carbazoles, [51][52][53][54][55][56][57][58] benzophenones, [59][60][61][62][63][64] pyrenes, [65][66][67][68][69][70] diketopyrrolopyrroles, [71]...…”

Developments of Smart Drug-Delivery Systems Based on Magnetic Molecularly Imprinted Polymers for Targeted Cancer Therapy: A Short Review

“…In addition, due to the easiness of turning the light on or off, spatial and temporal control of the initiation step can be reached; such behavior is not possible by heating. Thus, the development of new initiating systems able to initiate polymerization in such conditions is at the center of numerous research [176] due to the low-temperature conditions, facilitation of temporal and spatial control-and especially for practical application solvent-free formulation wavelength flexibility and high curing speed [175]. Nevertheless, as mentioned before, photopolymers possibly release residual monomers, photoinitiators and similar products resulting from decomposition processes into the environment [168].…”