Photoinduced processes have been widely utilized in macromolecular synthesis through radical, cationic, anionic, and controlled/living polymerizations and ligation processes. While widely utilized, their application in step-growth polymerization has been scarcely investigated. In the present work, we report a new facile photochemical approach for the synthesis of polypyrene (PPy) by step-growth polymerization. Inspired by our previous studies on photoinduced electron-transfer reactions occurring between electron-rich monomers such as thiophene and carbazole derivatives and iodonium salt, we show that pyrene (Py) readily polymerizes under 350 nm irradiation at room temperature in the presence of iodonium salt by consecutive excitation, electron transfer within the exciplex, proton release, and coupling reactions. A detailed investigation on the structural, morphological, electrochemical, and molecular weight characteristics of the polymers revealed that the ratio of iodonium salt/Py plays a crucial role in the chain length and properties. The approach developed here is broadly adaptable to functional pyrenes and other conjugated monomers.
We herein report photoinduced step‐growth polymerization of highly conjugated 2,5‐dithiophenyl (thieno[3,4‐b] thiophene) (TTs) derivatives possessing 4‐cyanophenyl or 4‐methoxyphenyl or 3‐(4‐fluorophenyl) groups substituted at the terminal position. Upon irradiation at 350 nm, the excited state of these molecules forms exciplex with diphenyliodonium hexafluorophosphate (DPI) that undergoes electron transfer reaction forming radical cations. Successive proton release and radical coupling reactions yield corresponding oligothienothiophenes with overall yields varying between 19–74%. Structural and molecular weight characteristics of the oligomers thus formed were investigated by Ultraviolet, fluorescence, NMR (Nuclear Magnetic Resonance) and infrared (IR) spectroscopic methods, and GPC (Gel Permeation Chromatography), respectively. The effect of substitution and dithiophene side groups on the reactivity of the monomer and band gap of the oligomers formed was evaluated by using cyclic voltammetry.
A new photochemical approach for the synthesis of metal-free three-dimensional hollow spherical conjugated polymers is described. Irradiation of solutions containing specially designed monomer, namely 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) possessing both carbazole and...
The construction of a rapid and easy immunofluorescence bioassay for SARS-CoV-2 detection is described. We report for the first time a novel one-pot synthetic approach for simultaneous photoinduced step-growth polymerization of pyrene (Py) and ring-opening polymerization of ε-caprolactone (PCL) to produce a graft fluorescent copolymer PPy- g -PCL that was conjugated to SARS-CoV-2-specific antibodies using EDC/NHS chemistry. The synthesis steps and conjugation products were fully characterized using standard spectral analysis. Next, the PPy- g -PCL was used for the construction of a dot-blot assay which was calibrated for applications to human nasopharyngeal samples. The analytical features of the proposed sensor showed a detection range of 6.03–8.7 LOG viral copy mL −1 (Ct Scores: 8–25), the limit of detection (LOD), and quantification (LOQ) of 1.84 and 6.16 LOG viral copy mL −1 , respectively. The repeatability and reproducibility of the platform had a coefficient of variation (CV) ranging between 1.2 and 5.9%. The fluorescence-based dot-blot assay was tested with human samples. Significant differences were observed between the fluorescence intensity of the negative and positive samples, with an overall correct response of 93.33%. The assay demonstrated a high correlation with RT-PCR data. This strategy opens new insights into simplified synthesis procedures of the reporter molecules and their high potential sensing and diagnosis applications. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s00604-022-05244-2.
Photoinduced radical and step-growth polymerizations of carbazole functional styrene (vinyl phenyl carbazole, VPC) by sequential and one-pot strategies have been investigated. The obtained polymers were characterized by FTIR, 1H-NMR, GPC, UV–Vis, PL, CV, and BET analyses. The theoretical charge distribution and HOMO–LUMO calculation by DFT were well-matched with those obtained from optical and electrochemical measurements. In the sequential approach, visible light-induced free-radical photopolymerization of VPC by using bisacyl phosphineoxide results in the formation of linear polymers with side-chain carbazole moieties. The resulting polymers exhibit a smooth surface as a consequence of decreasing crystallinity. As evidenced by TEM analysis, the subsequent photoiniated step-growth polymerization of the carbazole groups by using diphenyliodonium hexafluorophosphate (DPI) yields hyperbranched and cross-linked polymers with the microspheres on the surface. In the one-pot approach, concomitant photoinitiated free-radical and step-growth polymerizations by using DPI results in the formation of cross-linked polymers with dispersed distribution. The total nitrogen uptake of VPC-based polymers by using Brunauer–Emmett–Teller (BET) surface area was found to be between about 150 and 190 m2/g at 77 K.
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