Free radical photopolymerization initiated by UV and LED: Towards UV stabilized,tack free coatings

UV stabilizers (UV absorbers and Hindered Amine Light Stabilizers‐HALS) are added to UV‐curable formulations to provide long‐term durability. The influence of HALS and the filtering effect of UV absorbers are investigated under UV and LED irradiation by using different photoinitiating systems in free radical photopolymerization. The contribution of irradiation conditions and initiating systems on the filtering effect is discussed by performing Real‐Time Fourier Transform Infrared Spectroscopy (RT‐FTIR) and Confocal Raman Microscopy. Additionally, to get quantitative information about the light absorbed by the photoinitiator, without and with the filtering issue arising from UV stabilizers, series of calculations are carried out by taking into account the amount of light absorbed by the compounds and the intensity of the incident light. Finally, formulations are optimized with respect to surface inhibition to obtain tack free coatings in air atmosphere in the presence of UV stabilizers under visible light. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3597–3607     

Enzymatic Oxy- and Amino-Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C−O and C−N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials.     

Phenothiazine-based chalcones as potential dual-target inhibitors toward cholinesterases (AChE,BuChE) and monoamine oxidases (MAO-A,MAO-B)

Chalcones targeting neurodegenerative diseases have been known as attractive structures in drug design and discovery. In this study, phenothiazine-based chalcones as ChEs and MAOs inhibitors were designed and synthesized via base-catalyzed Claisen-Schmidt condensation, and chemical structures of the compounds were elucidated by NMRs and HRMS. Compounds 3 and 9 showed promising inhibition potency against AChE enzyme with IC₅₀ values of 0.221 μM and 0.053 μM while compound 9 displayed remarkable inhibition potency toward MAO-B enzyme with IC₅₀ value of 0.048 μM. Compound 9 , as a dual-target inhibitor, selectively inhibited AChE and MAO-B enzymes. This promising behavior is an advantage for the compound since MAO-B and AChE inhibition have a role in Alzheimer's disease. Fused tricyclic ring systems such as phenothiazine incorporated with chalcone moiety being multitargeting ligands may help scientists for the rational design of novel lead compounds targeting neurodegenerative illnesses.     

The effect of an aminoalcohol on the polymerization of acrylates with type II initiators

In this study, the authors report the use of an aliphatic amine and an aromatic aminoalcohol as synergists with various Type II initiators by using Photo-DSC (Photo-differential scanning calorimetry) technique. The photopolymerization of triacrylate and diacrylate was performed under nitrogen atmosphere in the presence of an amine or aminoalcohol with type II initiators, which allowed us to compare the efficiency of the initiating radicals. The oxygen scavenging role of the amine was left out.     

Synthesis,Characterization, Electrical Conductivity and Fluorescence Properties of Polyimine Bearing Phenylacetylene Units

In this study, a Schiff base was synthesized by the condensation reaction of 4-bromobenzaldehyde and 4-aminophenol. Then, phenylacetylene substituted Schiff base monomer (IPA) was obtained by HBr elimination reaction of IPA with phenylacetylene through Sonogashira reaction. IPA was polymerized via chemical oxidative polycondensation reaction. FT-IR and NMR measurements were used for the structural analyses of the synthesized substances. Fluorescence and UV–Vis analyses were carried out for optical characterization. Electrochemical characteristics, electrical conductivities and thermal properties were determined using cyclic voltammetry (CV), four-point probe conductometer, TG-DTA and DSC methods. The main purpose of the present study was to investigate the effects of phenylacetylene bearing units on the properties of conjugated aromatic polyimines. The spectral analysis signified a green light emission behavior when irradiated at different wavelengths. Combined with fluorescent behavior and good thermal stability, the electrical conductivity was found to be very crucial for π-conjugated polymer.     

Preparation and characterization of 3-[(1H-1,2,4-triazole-3-ylimino)methyl]naphtalene-2-ol film at the platinum surface for selective voltammetric determination of dopamine in the presence of uric acid and ascorbic acid

A [(1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol (TMN-2-ol) film modified platinum (Pt) electrode has been fabricated by the electrochemical oxidation in acetonitrile solution. The modified surface was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The prepared Pt electrode can be used as a functional interface to sensitive and selective determination of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA) by square wave voltammetry (SWV) method. The limit of detection (LOD) and limit of quantification (LOQ) of DA were 9.25 × 10⁻⁸ and 2.78 × 10⁻⁷ M, respectively. Linear range of DA was found to be between 3.95 × 10⁻⁷ and 4.19 × 10⁻⁶ M.     

Photoinitiated polymerization of β-cyclodextrin/methyl methacrylate host/guest complex in the presence of water soluble photoinitiator, thioxanthone-catechol-O,O′-diacetic acid

β-Cyclodextrin (β-CD) was used to complex the monomer, methyl methacrylate (MMA), yielding a water-soluble host/guest complex. Photoinitiated polymerization of β-CD/MMA complex was achieved in the presence of thioxanthone-catechol-O,O′-diacetic acid (TX-Ct), a one component water soluble photoinitiator. Photodecarboxylation of TX-Ct in water seems to be an important reaction mechanism. Therefore, resulting alkyl radicals are able to initiate the polymerization of β-CD/MMA host/guest complex in water.     

Poly(azomethine-epoxy-ether) containing phenyl and etoxy moieties: synthesis,characterization and fluorescence property

The design and synthesis of poly(azomethine-epoxy-ether) (PAZ-EP) containing epoxide moiety was described. The purpose of the research was the improvement of poly(azomethine-ether) containing epoxide by introduction of Schiff base moiety. PAZ-EP was synthesized using epichlorohydrin (EP). The structure of the Schiff base (SB) and PAZ-EP were verified by FT-IR, ¹H-NMR, ¹³C-NMR and UV–Vis spectroscopic analyses. Further characterization was employed using photophysical, electrochemical and fluorescence (PL) measurements. Application of TGA and differential scanning calorimetry analyses revealed thermal stability and thus propose a thermal processibility, which makes them potential materials for many contemporary practices. The number of average molecular weight of polymer with a polydispersity index of 1.14 was found to be 6750 Da using a gel permeation chromatography instrument. The highest occupied–lowest unoccupied energy levels and electrochemical (\(E_{\text{g}}^{'}\)) band gap values of PAZ-EP were determined by cyclic voltammetry (CV) measurement. Scanning electron microscopy (SEM) images were illustrated at different magnifications to study the morphologic property of PAZ-EP.