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

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.

Water-Soluble Visible Light Sensitive Photoinitiating System Based on Charge Transfer Complexes for the 3D Printing of Hydrogels

“…According to our previous works concerning mono -chalcone or bis -chalcone-based natural dyes, these compounds are basically soluble in organic solvents (such as acetonitrile) but insoluble or only slightly soluble in water [ 21 , 22 , 23 , 24 , 25 ]. Therefore, during the process of molecular design, we tried first to introduce a section of polyethylene glycol chain into the chalcone structure (as shown in Scheme 1 ) in order to increase the water solubility.…”

Recent advances on chalcone-based photoinitiators of polymerization

“…Comparisons of the photoinitiating abilities of the two different series of dyes revealed the series based on ferrocene to furnish lower monomer conversions than the methoxy-based series and these results are consistent with previous works reported in the literature and devoted to ferrocene-based chalcones that were also identified as furnishing lower monomer conversions than the purely organic chalcones. [240] It has to be noticed that in the literature, ferrocene has mostly been used as a cationic photoinitiator and not as an initiator for FRP processes, supporting the lower efficiency of the ferrocene-based chalcones. [55,234] In the present case, the slow photoreaction speed combined with the deep brown color of the different ferrocene-based chalcones adversely affecting the light penetration within the photocurable resin were suggested as possible explanations supporting the lower monomer conversions.…”

Recent advances on carbazole-based oxime esters as photoinitiators of polymerization

“…[35] Face to these considerations, polymerization of thick samples and even of resins containing fillers can be achieved. Reprinted with permission from Bonardi et al [35] Considering that the light penetration is the key parameter for achieving high monomer conversions, a wide range of structures have been examined ranging from truxene derivatives [36] to copper complexes, [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] carbazoles, [54][55][56][57][58][59][60][61][62][63][64][65] chalcones, [28,[66][67][68][69][70][71][72][73][74][75][76][77][78] zinc complexes, [79] acridones,…”