Poly(ethylene glycol)-thioxanthone prepared by Diels-Alder click chemistry as one-component polymeric photoinitiator for aqueous free-radical polymerization

Cyclopolymerizable and cyclopolymeric photoinitiators from diallyl amine and α-hydroxy ketones

Two novel cyclopolymerizable and one cyclopolymeric (first in the literature) PIs with high reactivity, controllable water solubility, migration stability and high thermal stability were synthesized by attachment of diallyl amine to I2959 or I184.

Allyl amino-thioxanthone derivatives as highly efficient visible light H-donors and co-polymerizable photoinitiators

Allyl-amino thioxanthone derivatives as new visible-light photoinitiators for efficient free-radical, cationic and thiol–ene polymerizations.

Photocatalysis in organic and polymer synthesis

This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.

Photocatalytic decarboxylation of diacids for the initiation of free radical polymerization

Photopolymerization, which is one of the most attractive polymerization methods, has been recently studied for the development of new photoinitiators. Herein, we use a binary mixture of titanium dioxide (TiO₂) nanoparticles and carboxylic diacid as a novel photoinitiator to initiate the free radical polymerization of vinyl acetate (VAc). The polymerization of VAc is achieved both in aqueous medium and bulk. The initiation mechanism of TiO₂/diacids is studied via nuclear magnetic resonance (NMR) spectroscopy using ¹³C labeled diacids as probing molecules. Further, a universal reaction mechanism is established, where the polymerization of VAc is initiated by the HOOC-R˙ radical, which is generated from the photocatalytic decarboxylation of the diacid. The polymerization kinetics results indicate that the polymerization rate is strongly dependant on the diacid structure. Compared to the use of diacids with an odd number of carbons, it is found that using diacids with an even number of carbons results in the polymerization rate reaching the maximum value faster.

Studies of the binding mode of TXNHCH2COOH with calf thymus DNA by spectroscopic methods

In this study, a thioxanthone derivative named 2-(9-oxo-9H-thioxanthen-2ylamino) acetic acid (TX-NHCH2COOH) was used to investigate small molecule and DNA binding interactions. Absorption and fluorescence emission spectroscopy were used and melting studies were used to explain the binding mode of TXNHCH2COOH-DNA. Intrinsic binding constant Kb TXNHCH2COOH was found 6×10(5)M(-1)from UV-Vis absorption spectroscopy. Fluorescence emmision intensity increased by adding ct-DNA to the TXNHCH2COOH and KI quenching experiments resulted with low Ksv value. Additionally, 3.7°C increase for Tm was observed. The observed quenching of EB and ct-DNA complex and increase viscosity values of ct-DNA by addition of TXNHCH2COOH was determined. All those results indicate that TXNHCH2COOH can intercalate into DNA base pairs. Fluorescence microscopy helped to display imaging of the TXNHCH2COOH-DNA solution.

Photoinduced Electron Transfer Reactions for Macromolecular Syntheses

Photochemical reactions, particularly those involving photoinduced electron transfer processes, establish a substantial contribution to the modern synthetic chemistry, and the polymer community has been increasingly interested in exploiting and developing novel photochemical strategies. These reactions are efficiently utilized in almost every aspect of macromolecular architecture synthesis, involving initiation, control of the reaction kinetics and molecular structures, functionalization, and decoration, etc. Merging with polymerization techniques, photochemistry has opened up new intriguing and powerful avenues for macromolecular synthesis. Construction of various polymers with incredibly complex structures and specific control over the chain topology, as well as providing the opportunity to manipulate the reaction course through spatiotemporal control, are one of the unique abilities of such photochemical reactions. This review paper provides a comprehensive account of the fundamentals and applications of photoinduced electron transfer reactions in polymer synthesis. Besides traditional photopolymerization methods, namely free radical and cationic polymerizations, step-growth polymerizations involving electron transfer processes are included. In addition, controlled radical polymerization and "Click Chemistry" methods have significantly evolved over the last few decades allowing access to narrow molecular weight distributions, efficient regulation of the molecular weight and the monomer sequence and incredibly complex architectures, and polymer modifications and surface patterning are covered. Potential applications including synthesis of block and graft copolymers, polymer-metal nanocomposites, various hybrid materials and bioconjugates, and sequence defined polymers through photoinduced electron transfer reactions are also investigated in detail.

Poly(vinyl alcohol)-Thioxanthone as One-Component Type II Photoinitiator for Free Radical Polymerization in Organic and Aqueous Media

A novel one-component type II polymeric photoinitiator, poly(vinyl alcohol)-thioxanthone (PVA-TX), is synthesized by a simple acetalization process and characterized. PVA-TX enables photopolymerization of methyl methacrylate and acrylamide in both organic and aqueous media. Photopolymerization proceeds even in the absence of a co-initiator since PVA-TX possesses both chromophoric and hydrogen donating sites in the structure.

Shining a light on an adaptable photoinitiator: advances in photopolymerizations initiated by thioxanthones

This review focuses on the advancements and progress in photoinitiated polymerization techniques mediated by thioxanthone (TX) and its derivatives.

Visible light initiating systems for photopolymerization: status, development and challenges

A review of recent advances in visible light initiating systems using free radical, cationic and hybrid photoinitiators is presented.

Hierarchically porous π-conjugated polyHIPE as a heterogeneous photoinitiator for free radical polymerization under visible light

A hierarchically porous π-conjugated polyHIPE was used as a heterogeneous visible light photoinitiator for the radical polymerization of methyl methacrylate (MMA) under a household energy saving light bulb at room temperature.

Mesoporous Graphitic Carbon Nitride as a Heterogeneous Visible Light Photoinitiator for Radical Polymerization

The use mesoporous graphitic carbon nitride (mpg-C₃N₄) in conjunction with tertiary amines as initiators in visible-light-induced free radical polymerization is described. The initiation mechanism involves photoinduced free radical generation by scavenging holes with amines and subsequent hydrogen abstraction. The efficiency of the photoinitiation is controlled by the nature of the amines and specific surface area of the carbon nitride powder. Apparently, amines with higher basicity and available hydrogens provide more favorable conditions for the photoinitiation process. Due to its heterogeneous nature, the photoinitiator preserves its photoinitiation activity after the polymerization and can easily be separated and used for further polymerizations.