One-pot synthesis of water-soluble polymeric photoinitiator via thioxanthonation and sulfonation process

Water-Soluble Photoinitiators in Biomedical Applications

Light-initiated polymerization processes are currently an important tool in various industrial fields. The advancement of technology has resulted in the use of photopolymerization in various biomedical applications, such as the production of 3D hydrogel structures, the encapsulation of cells, and in drug delivery systems. The use of photopolymerization processes requires an appropriate initiating system that, in biomedical applications, must meet additional criteria such as high water solubility, non-toxicity to cells, and compatibility with visible low-power light sources. This article is a literature review on those compounds that act as photoinitiators of photopolymerization processes in biomedical applications. The division of initiators according to the method of photoinitiation was described and the related mechanisms were discussed. Examples from each group of photoinitiators are presented, and their benefits, limitations, and applications are outlined.

Design of photoinitiator-functionalized hydrophilic nanogels with uniform size and excellent biocompatibility

Three well-controlled biocompatible hydrophilic nanogels were synthesized, and they can effectively initiate photopolymerization and improve the mechanical properties of polymers.

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.

Synthesis of well-defined bisbenzoin end-functionalized poly(ε-caprolactone) macrophotoinitiator by combination of ROP and click chemistry and its use in the synthesis of star copolymers by photoinduced free radical promoted cationic polymerization

A new well-defined bisbenzoin group end-functionalized poly(ε-caprolactone) macrophotoinitiator (PCL-(PI)2) was synthesized by combination of ring opening polymerization (ROP) and click chemistry. The ROP of ε-CL monomer in bulk at 110 °C, by means of a hydroxyl functional initiator namely, 3-cyclohexene-1-methanol in conjunction with stannous-2-ethylhexanoate, (Sn(Oct)2), yielded a well-defined PCL with a cyclohexene end-chain group (PCL-CH). The bromination and subsequent azidation of the cyclohexene end-chain group gave bisazido functionalized poly(ε-caprolactone) (PCL-(N3)2). Separately, an acetylene functionalized benzoin photoinitiator (PI-alkyne) was synthesized by using benzoin and propargyl bromide. Then the click reaction between PCL-(N3)2 and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that poly(ε-caprolactone) with bisbenzoin photoactive functional group at the chain end (PCL-(PI)2) with controlled chain length and low-polydispersity was obtained. This PCL-(PI)2 macrophotoinitiator was used as a precursor in photoinduced free radical promoted cationic polymerization to synthesize an AB2-type miktoarm star copolymer consisting of poly(ε-caprolactone) (PCL, as A block) and poly(cyclohexene oxide) (PCHO, as B block), namely PCL(PCHO)2.

High-performance 3D printing of hydrogels by water-dispersible photoinitiator nanoparticles

In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)-visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode-based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents.

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.

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.