New pyridinium salts as versatile compounds for dye sensitized photopolymerization

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

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.

Photoinduced free radical promoted cationic polymerization 40 years after its discovery

Free radical promoted cationic photopolymerization has been described with its historical background, main principles and usage in polymer synthesis.

N-[2-(Dimethylamino)ethyl]-1,8-naphthalimide derivatives as photoinitiators under LEDs

Four N-[2-(dimethylamino)ethyl]-1,8-naphthalimide derivatives (ANNs) with different substituents in the naphthalimide skeleton have been synthesized and can be used as versatile photoinitiators under various LEDs.

Synthesis and in vitro antimicrobial evaluation of new N-heterocyclic diquaternary pyridinium compounds

A series of bis-pyridinium quaternary ammonium salts (bis-PyQAs) with different aryl and heteroaryl moieties were synthesized and their antimicrobial activity investigated. The inhibition effect of the compounds was evaluated against bacteria, molds and yeasts; the activities were expressed as the minimum inhibitory concentrations (MIC). The relationships between the structure descriptors (logP, polarizability, polar surface area (2D), van der Waals area (3D)) and the biological activity of the tested bis-PyQAs are discussed.

Panchromatic Photopolymerizable Cationic Films Using Indoline and Squaraine Dye Based Photoinitiating Systems

The photoinitiating abilities of indoline and squaraine dyes (D102 and SQ02) incorporated in multicomponent systems for the cationic polymerization of an epoxide or a vinyl ether have been investigated. The polymerizable films exhibit a panchromatic character as revealed by their photosensitivity to a halogen lamp (370-800 nm); household LED bulbs centered at 462 nm (blue), 514 nm (green), 591 nm (yellow), and 630 nm (red); and laser diodes at 457, 473, 532, and 635 nm. SQ02 is particularly efficient in the 520-700 nm range, while D102 exhibits a good efficiency in the 400-580 nm region. The radical photopolymerization of an acrylate can also be observed particularly at 635 nm or upon a halogen lamp. The photochemical mechanisms are studied by steady state photolysis, fluorescence, cyclic voltammetry, electron spin resonance spin trapping, and laser flash photolysis techniques.

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

Eleven di- and trifunctional compounds based on a core-pyrene π structure (Co_Py) were synthesized and investigated for the formation of free radicals. The application of two- and three-component photoinitiating systems (different Co_Pys with the addition of iodonium or sulfonium salts, alkyl halide or amine) was investigated in detail for cationic and radical photopolymerization reactions under near-UV-vis light. The proposed compounds can behave as new photocatalysts. Successful results in terms of rates of polymerization and final conversions were obtained. The strong MO coupling between the six different cores and the pyrene moiety was studied by DFT calculations. The different chemical intermediates are characterized by ESR and laser flash photolysis experiments. The mechanisms involved in the initiation step are discussed, and relationships between the core structure, the Co_Py absorption property, and the polymerization ability are tentatively proposed.