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

Nicolas Giacoletto,Frédéric Dumur

doi:10.3390/molecules26113192

Abstract

Over the past several decades, photopolymerization has become an active research field, and the ongoing efforts to develop new photoinitiating systems are supported by the different applications in which this polymerization technique is involved—including dentistry, 3D and 4D printing, adhesives, and laser writing. In the search for new structures, bis-chalcones that combine two chalcones’ moieties within a unique structure were determined as being promising photosensitizers to initiate both the free-radical polymerization of acrylates and the cationic polymerization of epoxides. In this review, an overview of the different bis-chalcones reported to date is provided. Parallel to the mechanistic investigations aiming at elucidating the polymerization mechanisms, bis-chalcones-based photoinitiating systems were used for different applications, which are detailed in this review.

Highlights

Polymerization consists of converting a liquid resin into a solid, and different approaches can be used to obtain this result
As the most popular approach, the polymerization can be instigated by heat, and for this purpose, various thermal polymerization techniques have been developed over the years—such as ring-opening polymerization (ROP) [1,2], reversible addition–fragmentation chain-transfer (RAFT) polymerization [3], and nitroxide-mediated polymerization (NMP) [4,5,6]
Photopolymerization was mostly based on UV photoinitiating systems, UV light is the focus of numerous safety concerns, such that a great deal of effort is being devoted to developing visible light photoinitiating systems offering safer working conditions for the operator [7,8,9,10,11,12,13,14,15,16]

Summary

Introduction

Polymerization consists of converting a liquid resin into a solid, and different approaches can be used to obtain this result. The development of visible light photoinitiating systems is supported by the easy access to cheap, compact, lightweight, and energy-saving irradiation sources such as light-emitting diodes (LEDs) [21,22] Faced with this easy availability of LEDs with tunable irradiation wavelengths, the demand for photopolymerizable resins activable at these different wavelengths has increased. With the aim of generating initiating species, two distinct families of photoinitiators can be distinguished: The first family, type I photoinitiators, consists of molecules that can be photochemically cleaved upon excitation The advantage of this strategy is that only a single component is nec-. Comparisons with reference compounds will be established in order to demonstrate the potential of these new structures for photoinitiation

The Different Synthetic Routes to bis-Chalcones

C56 C57 C58 C59 blank

Findings

Conclusions