Azobis 2-methylpropionamidine Dihydrochloride Research Articles

S,N-rich luminous covalent organic frameworks for Hg2+ detection and removal

The challenge for simultaneous detection and removal of Hg2+ is the design of bifunctional materials bearing abundant accessible chelating sites with high affinity. Covalent-organic frameworks (COFs) are attracting more and more attention as potential bifunctional materials for Hg2+ detection due to their large specific surface area, ordered pores, and abundant chelating sites. Here, a new luminous S,N-rich COFBTT-AMPD based on hydrophilic block unit of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AMPD) was constructed, which improved the solubility and affinity for Hg2+ greatly. Another S-rich fused-ring unit of benzotrithiophene tricarbalaldehyde (BTT) enhanced the conjugation of COFBTT-AMPD, and the methyl-rich chains block unit of AMPD effectively suppressed the aggregation-caused quenching. Thus, the COFBTT-AMPD emitted strong fluorescence at 546 nm in liquid and solid as well as different solvent with a wide pH range, which was used for the visual detection and removal of Hg2+ (detection limit: 2.6 nM, linear range: 8.6 × 10−3-20 μM, monolayer adsorption capacity: 476.19 mg g−1) successfully. COFBTT-AMPD-based fabric and light-emitting diode coatings were further constructed to realize the visual detection of Hg2+ vapor. The results reveal the potential of S,N-rich luminous COFBTT-AMPD for Hg2+ detection and remediation in the environment.

Preparation, characterization, and antibacterial activity of cationic nanopolystyrenes

ABSTRACTCationic nanopolystyrenes (CNPSs) were prepared by the polymerization of styrene with a cationic polymerizable emulsifier, N‐(2‐(methacryloyloxy)ethyl)‐N,N‐dimethyltetradecane‐1‐ammonium bromide (MDTB), in the presence of 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (APPH). The polymerization kinetics was investigated through monomer conversion versus polymerization time. 1H NMR spectra and FTIR spectra were used to confirm the structures of MDTB and nanopolymers. The particle size, ζ‐potential, molecular weight, and thermal stability were also investigated by Zetasizer, gel permeation chromatography, and thermogravimetric analysis, respectively. The antibacterial activities of the obtained products were evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Staphylococcus aureus ATCC 29913 (S. aureus, a Gram‐positive bacterium) and Escherichia coli ATCC 25922 (E. coli, a Gram‐negative bacterium). The results indicated that the polymerization has the characteristics of microemulsion polymerization, all nanopolystyrenes are cationic and can be stored in the form of a microemulsion in aqueous phase, CNPSs present stable chemical structure at 190 °C, and their MIC and MBC reach 0.0625 and 0.125 mg mL−1 for E. coli, 0.0325 and 0.0625 mg mL−1 for S. aureus, respectively. Therefore, CNPSs are a promising new type of polymer antimicrobial agent, which can be used in the development of antimicrobial polymer materials and their products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48405.

Antioxidant Properties of Ferulic Acid Salts with Nicotine, Thionicotine and Selenonicotine

Background: Ferulic acid salts of nicotine and cotinine chalcogen analogs (thionicotine and selenonicotine) were characterized by spectroscopic methods. Antioxidant properties of all compounds prepared were evaluated. The obtained results indicated that thionicotine salt with ferulic acid was the most efficient to prevent the induced-oxidative haemolysis. Methods: The structure of salts was determined by ESI-MS and NMR methods. The antioxidant properties of all compounds prepared were evaluated by their reducing power, free radical scavenging activity and chelating capacity. Antioxidant and protective activities of compounds tested were compared with butylated hydroxytoluene (BHT) and Trolox, as standards. The capacity of all compounds to protect in vitro human erythrocytes from oxidative damage induced by 2,2'-azobis (2-methylpropionamidine) dihydrochloride (APPH) or tert-butyl hydroperoxide (t-BuOOH) was also estimated. Results: Ferulic acid forms the 1:1 salts with thionicotine and selenonicotine while 2:1 salt is formed with nicotine. Thionicotine salt with ferulic acid was the most efficient antioxidant (61.4% DPPH scavenging activity), as effective as standard Trolox (63%), and two times more effective than BHT (32.1%) at 1 mg/mL. Neither nicotine alkaloids and ferulic acid alone nor their salts, did not induce modification in the RBC shape or in their cell membrane permeability up to the concentration 1 mg/mL after 60 min or 24 h incubation Thionicotine salt with ferulic acid was the most potent inhibitor, as effective as Trolox and about 4 times more efficient than BHT at 1 mg/mL. Conclusion: Nicotine alkaloids salts with ferulic acid characterize an antioxidative potential and protect erythrocytes against oxidative-damage, therefore, they can be take into account for the further structureactivity studies in searching for new effective antioxidants. Keywords: Nicotine, thio- and selenoanalogs, ferulic acid, antioxidant properties, human erythrocytes, haemolysis

Studies on Micellization Behavior of Thermosensitive PNIPAAm-b-PLA Amphiphilic Block Copolymers

Thermo-sensitive amphiphilic block copolymers, poly(N-isopropylacrylamide)-block- poly(D,L-lactide) (PNIPAAm-b-PLA), were synthesized through a simple free radical copolymerization route based on a bifunctional initiator, 2,2'-azobis(2-methylpropion amidine) dihydrochloride (AMAD), followed by the ring-opening polymerization of D,L-lactide in the presence of Sn(Oct)2 catalyst. The Chemical structure characterization were conducted by means of 1H NMR, FT-IR, GPC. The amphiphilic PNIPAAm-b-PLA block copolymers could self-assemble into micelles with regularly spherical shape in an aqueous solution, with a TEM diameter range of 46-56 nm, DLS hydrodynamic diameter of 158-199 nm. This behavior depends on the environmental temperature, the hydrophobic interactions among PNIPAAm molecular chains, intermolecular hydrogen bonding between the PNIPAAm chains and water molecules as well as intramolecular hydrogen bonding between -CONH2 groups. The copolymers held a CMC from 5.50 to 6.17 mg L(-1) and LCST from 31.41-32.03 degrees C, being more or less affected by their compositions, PLA or PNIPAAm block length. The as-prepared PNIPAAm-b-PLA block polymers are anticipated to be applied as a potential candidate of drug release carriers.

Use of chelating solvent-based pressurized liquid extraction combined with inductively coupled plasma-optical emission spectrometry for trace element determination in atmospheric particulate matter

The feasibility of pressurized chelating solvents [ethylenediaminotetracetic acid (EDTA) dipotassium salt, 1,10-ortho-phenanthroline (PHEN), 8-hydroxyquinoline (8HQ), chloramine-T (CT), 1,1,1-trifluoro-2,4-pentanedione (H(fta)), 2,2′-azobis-(2-methylpropionamidine) dihydrochloride (AMPAHC) and 1,5-diphenylcarbazone (DFC)] has been investigated from a novel aspect to speed up metals leaching from atmospheric particulate matter (PM10). The target elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, V and Zn) have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The highest metal recoveries (within the 85–100% range) were found when using EDTA. Variables inherent to pressurized liquid extraction (temperature, chelating solvent concentration, static time, pressure, number of cycles, dispersing agent mass, flush volume and purge time) were simultaneously studied by applying a Plackett–Burman design (PBD) as the screening method. Results showed statistical significance for some factors such as extraction temperature and EDTA concentration. The static time and the number of cycles were statistically non-significant for most of the elements, meaning that the pressurized leaching procedure can be finished after 12 min (5 min for pre-heating the extraction cell at 100 °C plus 5 min of static time plus 1 min of purge time plus 1 min of end relief time). In addition, the presence of dispersing agent was not necessary, which reduces the time for filling of the cells. Quantitative recoveries for all metals were reached under the following extraction conditions: 40 mM EDTA, extraction temperature of 100 °C, pressure of 1000 psi, static time of 5 min and one extraction cycle. Analytical performances, such as limits of detection and quantification and repeatability of the over-all procedure, have been established. Finally, results obtained by EDTA-based pressurized liquid extraction have been found to be statistically comparable with those obtained after conventional acid digestion with nitric, hydrofluoric and perchloric acids.

Monomers for Adhesive Polymers, 5

AbstractSummary: 2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate (1) was synthesized by silylation of 2,4,6‐trimethylphenyl 2‐[4‐(dimethoxyphosphoryl)‐2‐oxa‐butyl]acrylate with trimethylsilyl bromide (TMSBr) and the hydrolysis of the silyl ester resulted in the formation of polymerizable phosphonic acid 1. The structure of this new monomer was characterized by IR, 1H, 13C and 31P NMR spectroscopy. The monomer dissolves well in ethyl acetate, ethanol or water and shows a high hydrolytic stability. 1 was homopolymerized with 2,2′‐azobisisobutyronitrile (AIBN), 2,2′‐azobis‐(2‐methylpropionamidine) dihydrochloride (AMPAHC) or dibenzoyl peroxide (DBPO) as the initiators. In a tetrahydrofuran (THF) solution, the deviations from the standard reaction kinetics were comparable with those of polymerizations of the other water soluble acrylate monomers. The unusual polymerization rate‐monomer concentration dependence with monomer intensity exponent less than 1 (m = 0.5) observed in THF solutions was even more declined from 1 in the polar medium EtOH‐H2O. The DBPO was a more effective polymerization initiator than AIBN. However, the overall activation energy of 81 kJ · mol−1 showed a usual temperature‐rate dependence observed in methacrylate ester polymerizations. In addition, monomer 1 was copolymerized with methyl methacrylate (MMA), ethyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate (2), and N,N′‐diethyl‐1,3‐bis(acrylamido)propane (3), respectively, using THF as the solvent and AIBN as the initiator. The copolymerization curves revealed only slight deviations from the ideal copolymer‐feed composition. The estimated copolymerization parameters indicate a ready incorporation of comonomer units into polymer chains, preferably by alteration rather than at random.2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate.image2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate.

Inhibition of free radical initiated peroxidation of human erythrocyte ghosts by flavonols and their glycosides.

The in vitro peroxidation of human erythrocyte ghosts was used as a model to study the free radical-induced damage of biological membranes and the protective effect of flavonols and their glycosides, i.e., quercetin (Q), quercetin galactopyranoside (QG), quercetin rhamnopyranoside (QR), rutin (R), morin (MO), kaempferol (K) and kaempferol glucoside (KG). The peroxidation was initiated by a water-soluble free radical initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) at physiological temperature, and monitored by oxygen uptake. Kinetic analysis of the peroxidation process demonstrates that these flavonols and their glycosides are effective antioxidants against AMPAD-initiated oxidative damage of human erythrocyte ghosts, and that the flavonols bearing ortho-dihydroxyl groups possess significantly higher antioxidant activity than those bearing no such functionalities and the glycosides are less active than their parent aglycones.

Monomers for Adhesive Polymers, 4

AbstractHydrolytically stable, crosslinking bis(acrylamide)s 1a–1l or bis(methacrylamide)s 2a–2c were synthesized by reaction of acryloyl or methacryloyl chloride using primary or secondary amines. In addition, monomers 3a and 3b were obtained by amidation of 2,6‐dimethylene‐4‐oxaheptane‐1,7‐dicarboxylic acid (DMOHDA) with propylamine and diethylamine, respectively. The structures of the monomers were characterized by IR, 1H, and 13C NMR spectroscopy. All monomers containing N,N′‐monosubstituted carbamide groups were solids. Those containing N,N′‐disubstituted carbamide groups were water‐soluble liquids. Water‐soluble bis(acrylamide) 1d (N,N′‐diethyl‐1,3‐bis(acrylamido)propane) shows a radical polymerization reactivity in the presence of 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (AMPAHC) similar to that of glycerol dimethacrylate, as revealed by gelation experiments in water. 1d is hydrolytically stable in 20 wt.‐% phosphoric acid and can be used to substitute dimethacrylates in self‐etching dentin adhesives. Furthermore, this monomer was also suitable as a reactive diluent in composites.magnified image

Grafting vinyl monomers onto silk (Bombyx mori) using different initiators: Properties of grafted silk

AbstractThe graft–copolymerization of silk with methacrylamide (MAA), 2‐hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA) was studied using three different free‐radical initiators: an inorganic peroxide [ammonium persulfate (APS)] and two azo compounds [2,2′‐azobisisobutyronitrile (AIBN) and 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (ADC)]. The rate and yield of grafting followed the order: APS > AIBN > ADC. The performance of AIBN was close to that of APS in terms of weight gain attained. The degree of yellowing of grafted silk varied as a function of the initiator–monomer system used. APS induced the highest degree of yellowing, regardless of which monomer was used, whereas silk grafted with the MAA/AIBN system displayed the lowest level of yellowing. Moisture regain of grafted silk changed as a function of the hydrophilic/hydrophobic character of the grafted polymer, regardless of the kind of initiator used. Accordingly, tensile properties showed a tendency to decrease with increasing weight gain of grafted silk, the extent of which was independent of the kind of monomer and initiator used. The different initiators did not induce any appreciable change in the fine structure of silk, as demonstrated by optical measurements. Uneven surface deposition of homopolymer was detected to variable extent with MMA and HEMA grafting, whereas the surface of MAA‐grafted silk was completely free of any foreign deposit, independently of the initiator used. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1401–1409, 2001

INTRODUCTION OF CATIONIC GROUPS ONTO CARBON BLACK SURFACE AND THEIR DISPERSIBILITY IN WATER

ABSTRACT Imidazoline hydrochlonde groups were successfully introduced onto carbon black surface by the treatment of imidazoline groups, which were introduced by the trapping of 2-(2-imidazolin-2-yl)propane radicals formed by the thermal decomposition of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (AJP) with hydrochloric acid. In addition, arrridine hydrochlonde groups were introduced onto carbon black surface by the radical trapping of 2-methylpropionamidine dihydrochloride radicals formed by the thermal decomposition of 22'-azobis(2-methylpropionamidine) dihydrochloride (AMPAD). The content of imidazoline hydrochlonde and amidine hydrochlonde groups introduced onto carbon black was determined to be 0.6 mmol/g and 0,7 mmol/g, respectively. The mean particle size of AIP/HCl-lreated and AMPAD-treated carbon black was determined to be 31 nm and 16 nm, respectively, by dynamic light scattering method. It was found that the surface of carbon black turned from hydraphobic to hydrophilic by the introduction of cationic moieties and gave a very stable colloidal dispersion in neutral and acidic water at room temperature.

Synergistic antioxidant effect of green tea polyphenols with α-tocopherol on free radical initiated peroxidation of linoleic acid in micelles

The antioxidant effect of the main polyphenolic components extracted from green tea leaves, i.e., (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG) and gallic acid (GA), against peroxidation of linoleic acid has been studied in sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) micelles. The peroxidation was initiated thermally by a water-soluble azo initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) and the reaction kinetics were followed by formation of linoleic acid hydroperoxides and consumption of the antioxidant. Kinetic analysis of the antioxidation process demonstrates that these green tea polyphenols are effective antioxidants in micelles used either alone or in combination with α-tocopherol (vitamin E). The antioxidative action may involve trapping the initiating radicals in the bulk water phase, trapping the propagating lipid peroxyl radicals on the surface of the micelle and regenerating α-tocopherol by reducing α-tocopheroxyl radical. The antioxidant activity of these green tea polyphenols depends significantly on the microenvironment of the reaction medium, the oxidation potential and the size of the molecule.

Antioxidant effect of coumarin derivatives on free radical initiated and photosensitized peroxidation of linoleic acid in micelles

The antioxidant activity of 4-methylcoumarin (MC), 6-hydroxy-4-methylcoumarin (HMC) and 7,8-dihydroxy-4-methylcoumarin (DHMC), respectively, in the inhibition of peroxidation of linoleic acid in micellar systems has been studied. The peroxidation was initiated either thermally by water-soluble initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) or photochemically by a triplet sensitizer benzophenone (BP) in the anionic micelle sodium dodecyl sulfate (SDS) or in the cationic micelle cetyl trimethylammonium bromide (CTAB). It was found that DHMC is a good antioxidant for both AMPAD-initiated and BP-sensitized peroxidation in both SDS and CTAB micelles, while HMC is only active for BP-sensitized peroxidation in SDS micelles. MC is ineffective in any case. The antioxidative action of the coumarin derivatives may include trapping the initiating radicals, trapping the propagating lipid peroxyl radicals, recycling α-tocopherol and/or deactivating the excited photosensitizer.

Inhibition of in vitro lipid peroxidation by stable steroidic nitroxyl radicals

4′,4′-dimethylspiro (5 α-cholestane-3,2′-oxazolidin)-3′-yloxy (IK-1) and 7 α,12 α-dihydroxy-4′,4′-dimethylspiro (5 β-cholan-24-oic-3,2′-oxazolidin)-3′-yloxy acid (IK-2), two stable steroidic nitroxyl radicals, were newly synthesized and tested as possible inhibitors of lipid peroxidation, induced by Fenton's reagent in both rat liver microsomes and egg phosphatidylcholine liposomes. The inhibitory activity, evaluated through the formation of thiobarbituric acid reactive substances (TBARS) and the conjugated diene, was compared with that of α-tocopherol and 2,2,6,6-tetramethylpiperidine-1-yloxy (TEMPO). In each model system IK-1 and IK-2 exhibited an IC 50 of 8 μM and reduced the formation of TBARS and conjugated diene, showing IK-1 a potency comparable to α-tocopherol and higher than TEMPO. Moreover IK-1 and, to a lesser extent IK-2, reduced the lipid peroxidation induced in the microsomes by the water-soluble azo-initiator 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AMPH), indicating the IK-1 and IK-2 ability as chain-breaking antioxidants. The hydroxylamine 4′,4′-dimethylspiro (5 α-cholestane-3,2′-oxazolidin)-3′-hydroxide (IK-3), obtained by chemical reduction of IK-1, was completely inactive as an inhibitor of lipid peroxidation in heat pre-treated microsomes and in liposomes. However in microsomes it was active since it was oxidized to the corresponding nitroxyl radical IK-1.