Photochromic Polymers Based on Fluorophenyl Oxime Ester Photoinitiators as Photoswitchable Molecules

Abstract

We designed and synthesized two novel fluorophenyl oxime ester photoinitiators (E-FBOXEs) with the ability to prepare photochromic polymers, and then photochromic polymers based on E-FBOXEs were prepared by fast photopolymerization. E-FBOXEs can initiate photopolymerization of tripropylene glycol diacrylate under UV LED irradiation at 395 nm, and the final double bond conversion is achieved up to 81%. Meanwhile, the photocured film (PTPGDA) initiated or doped with E-FBOXE-Me displays thermally reversible photochromism at a moderate temperature (50 °C), switching from brown to colorless, because the photochromism of E-FBOXE-Me depends on the cleavage of the N–O bond, resulting in the generation of acetoxy radicals and colored iminyl radicals in the planar conformation under irradiation at 395 nm, and the recombination of the radicals to form colorless E-FBOXE-Me molecules in the nonplanar conformation under heating. Importantly, the PTPGDA film exhibits good fatigue resistance. The E-FBOXEs have great potential for application in the preparation of photochromic polymeric materials.

Methyl Benzoylformate Derivative Norrish Type I Photoinitiators for Deep-Layer Photocuring under Near-UV or Visible LED

“…Significantly, N-MBF possesses the most excellent absorption property under the common LED emission wavelengths, followed by the commercial BAPO, and other investigated PIs exhibit lower molar extinction coefficients such as 10 M −1 cm −1 at 405 nm for MBF and F-MBF, but that does not mean they do not possess photoinitiating ability under LED emission wavelength because the initiating performances of PIs do not depend only on their light absorption properties. 26 Two lowest-energy electronic transitions, transitions type, energy gap of S 0 → S 1 , and the frontier molecular orbits for MBFs are shown in Figures S21−S31 and Table S2. The two lowest-energy transitions of MBFs for S 0 → S 1 are n−π* transition characteristics or π−π* transition characteristics.…”

“…However, the absorption wavelength of TF-MBF is blue shifted by more than 9 nm compared with MBF even though the molar extinction coefficient of TF-MBF is greater, which is because the trifluoromethyl group in the TF-MBF molecule is a very strong electron-withdrawing group and cannot be conjugated with the benzene ring. Significantly, N-MBF possesses the most excellent absorption property under the common LED emission wavelengths, followed by the commercial BAPO, and other investigated PIs exhibit lower molar extinction coefficients such as 10 M –1 cm –1 at 405 nm for MBF and F-MBF, but that does not mean they do not possess photoinitiating ability under LED emission wavelength because the initiating performances of PIs do not depend only on their light absorption properties …”

“…A few Norrish type I PIs including acylphosphine oxides, − oxime esters, ,,− naphthalimide aryl sulfide derivatives, , and α-dicarbonyls − for LED-induced photopolymerization have been reported recently. However, they still have some drawbacks.…”

Chaotropic Effect Stabilized Radical‐Containing Supramolecular Organic Frameworks for Photothermal Therapy

“…[ 1–5 ] Due to the unique magnetic, electronic, and optical properties, organic radicals play important roles in molecular magnets, [ 6 ] electronic devices, [ 7–9 ] catalysis, [ 10–13 ] photochemistry. [ 14–19 ] In particular, radical‐containing frameworks (RCFs), such as radicals incorporated in covalent organic frameworks (COFs) and metal organic frameworks (MOFs), have emerged as promising functional materials in gas adsorption, [ 20 ] photoluminescence, [ 21 ] photothermal therapy, [ 22–25 ] catalysis, [ 26,27 ] and magnetism. [ 28,29 ] However, organic radicals are not easily existing stable due to their unpaired valence electron, to further constructing them into ordered frame structure may face more difficult challenges, such as designing radical containing ligands, keeping organic radicals stable during synthesis, avoiding electrostatic repulsion of the organic radicals.…”

Novel chalcone derivatives with large conjugation structures as photosensitizers for versatile photopolymerization

“…The use of light‐emitting diodes (LEDs) for photopolymerization applications have recently generated increased attention because of their efficient light output and low cost 18–20 . However, the development of new and efficient LED‐sensitive PIs and PISs, such as oxime esters, 21–25 D‐π‐A‐containing photoacid generators, 16,18,26,27 and host–guest dye PIs, including ion‐pair complexes, 28–30 is challenging.…”