3-Carboxylic Acid and Formyl-Derived Coumarins as Photoinitiators in Photo-Oxidation or Photo-Reduction Processes for Photopolymerization upon Visible Light: Photocomposite Synthesis and 3D Printing Applications.

Mahmoud Rahal,Jacques Lalevée,Joumana Toufaily,Guillaume Noirbent,Bernadette Graff,Didier Gigmes,Frédéric Dumur,Tayssir Hamieh

doi:10.3390/molecules26061753

Abstract

In this paper, nine organic compounds based on the coumarin scaffold and different substituents were synthesized and used as high-performance photoinitiators for free radical photopolymerization (FRP) of meth(acrylate) functions under visible light irradiation using LED at 405 nm. In fact, these compounds showed a very high initiation capacity and very good polymerization profiles (both high rate of polymerization (Rp) and final conversion (FC)) using two and three-component photoinitiating systems based on coum/iodonium salt (0.1%/1% w/w) and coum/iodonium salt/amine (0.1%/1%/1% w/w/w), respectively. To demonstrate the efficiency of the initiation of photopolymerization, several techniques were used to study the photophysical and photochemical properties of coumarins, such as: UV-visible absorption spectroscopy, steady-state photolysis, real-time FTIR, and cyclic voltammetry. On the other hand, these compounds were also tested in direct laser write experiments (3D printing). The synthesis of photocomposites based on glass fiber or carbon fiber using an LED conveyor at 385 nm (0.7 W/cm2) was also examined.

Highlights

The development of new low-cost, environmentally friendly, and energy-efficient polymer synthesis remains more than ever at the heart of academic and industrial concerns and the subject of many new research strategies
Three families of coumarins have been examined as photoinitiators of polymerization
First family concerned coumarin-3ined as photoinitiators of polymerization

Summary

Introduction

The development of new low-cost, environmentally friendly, and energy-efficient polymer synthesis remains more than ever at the heart of academic and industrial concerns and the subject of many new research strategies. Photopolymers are present in several fields such as coatings [5], dentistry [6], automotive [7], cosmetics [8], 3D printing, and holography [9], etc. For most of these industrial fields, photochemical polymerization uses ultraviolet radiation, a technique widely known as UV curing. This pathway based on UV lamps (Hg lamps) remains energy-consuming. Alternatives to UV lamps and the use of longer wavelengths (near UV or visible) can be advantageous

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