Synthesis and characterization of chlorinated paraffin wax-bound paraphenylenediamine antioxidant and its application in natural rubber

p-Phenylenediamine was chemically attached to low molecular weight chlorinated paraffin wax. The polymer-bound p-phenylenediamine was characterized by vapor-phase osmometry (VPO), proton magnetic resonance spectroscopy (¹H-NMR), infrared spectroscopy (IR), and thermogravimetric analysis (TGA). The efficiency and permanence of the polymer-bound p-phenylenediamine as an antioxidant was compared with a conventional amine-type antioxidant in natural rubber vulcanizates. The vulcanizates showed improved aging resistance in comparison to vulcanizates containing a conventional antioxidant. The presence of liquid polymer-bound p-phenylenediamine also reduces the amount of the plasticizer required for compounding. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2183–2189, 2001     

Synthesis,Structure, and Explosive Properties of a New Trinitrate Derivative of an Unexpected Condensation Product of Nitromethane with Glyoxal

In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solution of sodium hydroxide, 3,6‐dinitro‐cyclohexane‐1,2,4,5‐tetraol was obtained (the expected product, described in the literature) and, unexpectedly, also tricyclic nitro‐triol (6b‐nitrohexahydro‐2H‐1,3,5‐trioxacyclopenta[cd]‐pentalene‐2,4,6‐triol), which has been unknown until now, was obtained as the main product. The structure of the compound was confirmed with ¹H NMR and ¹³C NMR spectroscopy, LR, and HR‐MS techniques and with single‐crystal X‐ray diffractometry. The tricyclic triol (formally a hemiacetal) was transformed into 6b‐nitrohexahydro‐2H‐1,3,5‐trioxacyclopenta[cd]‐pentalene‐2,4,6‐triyl trinitrate by reaction with 98 % HNO₃. Some explosive properties of this compound were determined including: friction and impact sensitivity, activation energy, detonation velocity, heat of combustion in an oxygen atmosphere and enthalpy of formation. The nitrate ester is a powerful explosive with performance close to that of pentaerythritol tetranitrate (PETN).     

A novel compound, 12,13,17-trihydroxy-9(Z)-Octadecenoic acid,from linoleic acid by a new microbial isolateClavibacter sp. ALA2

A novel compound, 12,13,17-trihydroxy-9(Z)-octadecenoic acid (THOA), was produced from linoleic acid by microbial transformation at 25% yield. The newly isolated microbial strain that catalyzed this transformation was identified asClavibacter sp. ALA2. The product was purified by high-pressure liquid chromatography, and its structure was determined by¹H and¹³C nuclear magnetic resonance, Fourier transform infrared, and mass spectroscopy. Maximum production of THOA was reached after 85 h of reaction. THOA was not further metabolized by strain ALA2. This is the first report on 12,13,17-trihydroxy unsaturated fatty acid and its production by microbial transformation.     

Preparation,structural characterization,and antioxidative behavior in natural rubber of antioxidant GM functionalized nanosilica

To restrain the migration and extractability of the antioxidants and improve the dispersion of nanosilica in natural rubber (NR), antioxidant 2‐tert‐butyl‐6‐(3‐tert‐butyl‐2‐hydroxy‐5‐methylbenzyl)‐4‐methyphenyl acrylate (GM) functionalized nanosilica was prepared using antioxidant coupling agent (KH590‐GM) as functional modifier, which was first synthesized through thiol‐ene reaction between the mercapto group of γ‐mercaptopropyl trimethoxysilane (KH590) and the CC double bonds of antioxidant GM. Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance confirmed the structure of KH590‐GM and GM functionalized nanosilica. Thermogravimetry analysis indicated that the grafting rate of GM functionalized nanosilica reached 13.4%, and the antioxidant had good thermal stability. Scanning electron microscope and mechanical properties measurement showed GM functionalized nanosilica was dispersed uniformly in NR vulcanizates, and helpful for the increase of the tensile strength and tensile stress of NR vulcanizates. Based on the study of the antioxidative behavior and extraction resistance of the NR vulcanizates, it was found that in contrast to NR vulcanizates with GM, the ageing coefficient and oxidation induction time of that with GM functionalized nanosilica increased to 0.66 and 39 min from 0.58 and 30 min, respectively. Furthermore, the NR vulcanizates with GM functionalized nanosilica also exhibited excellent extraction resistance. POLYM. COMPOS., 38:1241–1247, 2017. © 2015 Society of Plastics Engineers     

Distribution and Antioxidant Activities of Free,Conjugated, and Insoluble-Bound Phenolics from Seven Species of the Genus Camellia

Free phenolic (FP), conjugated phenolic (CP), and insoluble-bound phenolic (IBP) acids were extracted from the seeds of seven species of oil-tea camellia and their antioxidant activities were evaluated. The results indicated that Camellia vietnamensis has the highest total phenolic content (TPC) (31.84 ± 0.11 g of gallic acid equivalent [GAE] kg⁻¹) and that Camellia polyodontia has the lowest TPC (12.34 ± 0.22 g GAE kg⁻¹) in the kernel. The average TPC among the species is similar in both the kernels and in the shells, and the content order of the three forms of phenolic compounds is FP > IBP > CP. HPLC-MS analysis showed the presence of 9–11 phenolic compounds in the FP, CP, or IBP extracts of the seven species of oil-tea camellia seed. Among the phenolics identified, ferulic acid, catechin, and epicatechin were the major contributors of antioxidant activity. Hierarchical cluster analysis conducted based on the phenolic properties showed that C. vietnamensis and Camellia semiserrata belong to the group characterized by high antioxidant capacities (FRAP, ferric-ion-reducing antioxidant power; ABTS assay), and Camellia chekiangoleosa and Camellia oleifera are arranged in a group with moderate phenolic properties. The other species constitute the third cluster with low phenolic content and antioxidant activity. The study demonstrated that oil-tea camellia seed contains significant amounts of phenolic acids. In addition, extracts from various parts of the seed could be interesting novel sources of natural antioxidants.     

Extraction and identification of an antioxidative component from peanut hulls

Methanol extraction of hulls from Tainan select no. 9 (P-9) and Tainan no. 11 (P-11) peanuts produced a higher yield of a component having stronger antioxidant activity (AOA) than other organic solvents. The AOA of methanolic extracts from peanut hulls was equal to butylated hydroxyanisole and stronger thanα-tocopherol. The methanolic extract from peanut (P-11) hulls was separated into 18 fractions by thin-layer chromatography (TLC). High antioxidant activity was found in subfractions with R_fs of 0.20, 0.25, 0.28, 0.31 and 0.37 at 95.6%, 93.8%, 94.7%, 92.0% and 81.6% inhibition of peroxidation of linoleic acid, respectively. Further purification of the subfraction eluting at 0.20 yielded a compound with antioxidant activity of 94.8%. Based on high-performance liquid chromatography (HPLC) analysis, ultraviolet (UV) spectra and¹H nuclear magnetic resonance (NMR), this compound was identified as luteolin.     

Extraction and identification of natural antioxidant from the seeds of the Moringa oleifera tree variety of Malawi

The oil from the dried seeds of the Moringa oleifera tree (variety of Malawi) was extracted with a mixture of chloroform/methanol (50∶50). The induction period measurements demonstrated a great resistance to oxidative rancidity. After degumming, there was a reduction of 74% in induction periods. The gums produced were extracted with diethylether, n-butanol, and water, yielding four fractions: Fraction 1 (81.8% w/w), Fraction 2 (0.04% w/w), Fraction 3 (0.05% w/w), and Fraction 4 (17.0% w/w). These fractions were tested for their protection of fresh sunflower oil against rancidity, at 50°C, using a UV accelerated method. The oxidation of the sunflower oil was measured using PV; absorbance E _1cm ^1% and malondialdehyde concentration were measured by HPLC. The fraction that showed the highest antioxidant activity was further fractionated by HPLC, yielding seven fractions. Fraction HPLC 3 (present in a quantity of 330.8 and 29.11 ppm in gums and oil, respectively) showed the highest antioxidant activity. Its activity was also compared with that of the commonly used antioxidants BHT and α-tocopherol on sunflower oil using the same methods. At the same level of addition (200 ppm), HPLC 3 showed higher antioxidant activity than BHT and α-tocopherol. The identification of HPLC3 was done using ¹H NMR, ¹³C NMR, MS, melting point, and UV absorption spectroscopy and proved to be 3,5,7,3′,4′,5′-hexahydroxyflavone (myricetin).     

Identification and Synthesis of the Sex Pheromone of the Passionvine Mealybug, Planococcus minor (Maskell)

The sex pheromone of the mealybug, Planococcus minor was isolated by fractionation of crude pheromone extract obtained by aeration of virgin females. The pheromone was identified as the irregular terpenoid, 2-isopropyl-5-methyl-2,4-hexadienyl acetate, by mass spectrometry, microchemical tests, and ¹H NMR spectroscopy. The stereochemistry of the pheromone was assigned as (E) by comparison with synthetic standards of known geometry. The compound was highly attractive to males in laboratory bioassays, whereas the (Z)-isomer appeared to antagonize attraction.     

Synthesis and characterization of polyhydroxylated polybutadiene binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) with isophorone diisocyanate

A macromolecular hindered phenol antioxidant, polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was synthesized via a two‐step nucleophilic addition reaction using isophorone diisocyanate (IPDI) as linkage. First, the ? OH groups of PHPBT reacted with secondary ? NCO groups of IPDI to form the adduct PHPBT‐NCO, then the PHPBT‐b‐TPH was obtained by one phenolic ? OH of 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (TPH) reacting with the PHPBT‐NCO. The PHPBT‐b‐TPH was characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, and thermogravimetric analysis, and its antioxidant activity in natural rubber was studied by an accelerated aging test. Influences of reaction conditions on the two nucleophilic reactions between ? OH group and ? NCO group were investigated. In addition, catalytic mechanism for the reaction between PHPBT‐NCO and TPH was discussed. The results showed that the adduct PHPBT‐NCO could be obtained by using dibutyltin dilaurate (DBTDL) as catalyst, and the suitable temperature and DBTDL amount were 35°C and 3 wt %, respectively. However, triethylamine (TEA) was more efficient than DBTDL to catalyze the reaction between PHPBT‐NCO and TPH because of steric hindrance effect. In addition, it was found that the thermal stability and antioxidant activity of PHPBT‐b‐TPH were higher than those of the low molecular weight antioxidant TPH. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40942.     

Nanoparticles of a New Potassium(I) Coordination Polymer from Thermal Treatment with Oleic Acid: Syntheses, Characterization, Thermal, Structural and Solution Studies

Nanoparticles of a new potassium two-dimensional coordination polymer, {[K₂(μ₄-L)₂(μ-H₂O)₄]_n·nH₂O} (1), HL = 3-{[(4-nitrophenyl)methylen]amino}benzoic acid} were synthesized from thermal treatment of compound 1 with oleic acid at 523 K. The nanoparticles were characterized by scanning electron microscopy and FT-IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The crystal structure of this compound indicates that the coordination number for the potassium ions is seven. A hydrogen bonding network and π-π stacking interactions result in more stability of compound 1 crystal packing. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The results of stoichiometry studies and formation of compound 1 in MeCN solution were found to be in support of its solid state stoichiometry and show the 1:1 complex formation between the L⁻ and K⁺ ion in MeCN solution.     

Structure and Biosynthesis of Fimsbactins A–F,Siderophores from Acinetobacter baumannii and Acinetobacter baylyi

Novel chatechol/hydroxamate siderophores (named “fimsbactins”) were identified in Acinetobacter baumannii ATCC 17978 and Acinetobacter baylyi ADP1. The major compound, fimsbactin A, was isolated from low‐iron cultures of A. baylyi ADP1, and its chemical structure was elucidated by mass spectrometry, and detailed ¹H, ¹³C and ¹⁵N NMR spectroscopy. From inverse feeding experiments following HPLC‐MS analysis, the structures of five additional derivatives were elucidated. The gene cluster encoding the fimsbactin synthetase (fbs) was identified in both genomes, and mutants in fbs genes in A. baylyi were analyzed, thus allowing prediction of the fimsbactin biosynthesis pathway.     

Characterization of copolymeric poly(2-vinylimidazoline)

Copolymeric poly(2-vinylimidazoline), comprising the ring-closed 2-imidazoline and ring-opened linear amide repeat units, was characterized by ¹³C-NMR spectroscopy. This was facilitated by the ¹³C-NMR analyses of the model compound forms of the copolymer's repeat units, 2-ethylimidazoline and N-propionylethylenediamine. Quantitative determinations were made for the percentages of ring-opened, linear amide, repeat units and residual ethylenediamine present in different batches of the poly(2-vinylimidazoline) copolymer. © 1995 John Wiley & Sons, Inc.     

Synthesis, photopolymerization kinetics, and thermal properties of UV-curable waterborne hyperbranched polyurethane acrylate dispersions

A series of UV-curable waterborne hyperbranched polyurethane acrylate dispersions (WHBPUADs) were prepared via a three-step procedure based on isophorone diisocyanate (IPDI), hyperbranched polyester (HBP), maleic anhydride (MA), and hydroxy-ethyl acrylate (HEA). The structure of WHBPUADs was characterized by Fourier transform infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance spectroscopy (¹H NMR). FTIR was also applied to research the effect of double bond concentration on the kinetics of photopolymerization. The heat resistance of the cured films was characterized by thermogravimetric analysis (TGA), and their mechanical properties were also measured. The results showed that the double bond conversion (τ) and photopolymerization rate (R _p) were affected by the concentration of double bond and viscosity of WHBPUADs. The UV-curable systems with higher double bond concentration and lower viscosity led to higher τ and R _p. The maximum τ and R _p reached 93% and 71 mmol g⁻¹ s⁻¹, respectively. The WHBPUADs films possessed better heat resistance and mechanical properties, and with the increase of crosslink density, the heat resistance and hardnesses were further improved.     

Synthesis and characterization of triazine‐based dendrimers and their application in metal ion adsorption

This article described the synthesis of triazine‐based dendrimers with poly(ethylene glycol) core by convergent method. Compound 1 was prepared by coupling of amino group of diethanolamine with cyanuric chloride in dry THF (tetrahydrofuran). Reaction of compound 1 with p‐aminobenzylamine resulted in compound 2 . Compound 4 was synthesized using coupling reaction of amino group of compound 2 with cyanuric chloride, then coupling of amine groups of p‐aminobenzylamine with compound 3 in the hybrid solvents. The final dendrimer (den‐OH) were synthesized using reaction of dendron 4 with compound 5. Ethylene diaminetetraacetic acid modified final dendrimer were successfully prepared via coupling ethylene diaminetetraacetic acid dianhydride and den‐OH. The growth of dendrons and their structures were investigated by using usual spectroscopy methods and elemental analysis. The chelating behavior and sorption capacities of triazine dendrimers were determined in relation to pH dependency for some metal ions such as Cu⁺², Ni⁺², and Zn⁺² using atomic absorption methods. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Antioxidant activity of Magnolol, honokiol, and related phenolic compounds

The antioxidant activity of 10 Japanese and Chinese crude drugs (Kampo drugs) was determined in vitro. Extract of Magnolia cortex, which had the highest antioxidant activity, contained phenolic compounds magnolol and honokiol. However, inhibitory effects of these compounds on lipid oxidation were weaker than that of α-tocopherol as measured by thiobarbituric acid assay. The structure-activity relationship of phenolic compounds showed that antioxidant activities were in the order 4-allyl-2,6-dimethoxyphenol ≥ p,p′-biphenol > eugenol > 2-allyl-6-methylphenol > honokiol > magnolol > caffeic acid > p-ethylphenol > guaiacol. As expected, these results showed that an electron donor and/or bulky groups at the ortho- or para-position of the phenol were required for inhibition of lipid oxidation. Electron spin resonance spin trapping experiments showed that phenol compounds with an allyl substituent on their aromatic rings directly scavenged superoxide (O ₂ ⁻ ), and that only eugenol trapped hydroxyl radicals. These findings suggest that phenolic compounds that contain allyl groups may be effective antioxidants because of the scavenging ability of O ₂ ⁻ or hydroxyl radical, whereas other phenols, without an allyl moiety such as α-tocopherol, may play a role in the termination of free radical chain reactions.     

Assessment of the Physicochemical Properties and Oxidative Stability of Kernel Fruit Oil from the Acrocomia totai Palm Tree

This study investigated the effects of variations in oil contents and fatty-acid composition, density, viscosity, acid values, saponification values, specific oxidative stability, and antioxidant concentration of Acrocomia totai kernel oil during fruit maturation. Fatty acids were quantified using ¹H nuclear magnetic resonance (NMR) spectroscopy, gas chromatograph-flame-ionization detector (GC-FID), and Fourier transform Raman (FT-Raman) spectroscopy analyses. The results showed that all physicochemical characteristics and oil composition changed during the ripening stage. The CG-FID analysis showed a reduction in the unsaturated fatty-acid content (from 78.8% to 22.1%), with a proportional increase in the saturated fatty-acid contents (from 21.6% to 77.9%). The difference in the fatty-acid composition was confirmed by analysis of the ¹H NMR and FT-Raman spectra. The degree of unsaturation was calculated to determine the oxidative stability of oil. These results suggest that the fruit's maturation contributes to the specific oxidative stability. The antioxidant concentration revealed higher contents of carotenoids in the ripe fruit (0.16 mg of carotenoid per 100 g_KERNEL) when compared to the unripe fruit (0.05 mg of carotenoid per 100 g_KERNEL). In the total phenolics analysis, there was no change in concentration over ripening time. These results show that kernel oil has physicochemical properties comparable with high-quality commercial vegetable oils, suggesting that it is a promising alternative to conventional vegetable oils.     

Synthesis and polymerization of a novel oxirane bearing a cyclic acetal of salicylaldehyde chain moiety

The novel compound 2(1,3-dioxolan-2-yl)phenoxymethyloxirane was synthesized and anionically polymerized with potassium hydroxide, potassium hydride and potassium tert-butoxide. Polymers were characterized by ¹H and ¹³C NMR spectroscopy, size exclusion chromatography and electrospray mass spectrometry. Copyright © 2004 Society of Chemical Industry     

Unexploited Thapsia garganica,Orlaya maritima,and Retama raetam Seeds: Potential Sources of Unsaturated Fatty Acid and Natural Antioxidants

Total lipid contents, fatty acid compositions, phenolic profiles and antioxidants activities of seeds from Thapsia garganica, Orlaya maritima, and Retama raetam were investigated. The oil values were more than 26 %, except seeds of R. raetam (ca. 3 %). Unsaturated fatty acids accounted for the majority of the fatty acids (more than 75 %). Oleic and linoleic acid were the predominant fatty acids. Total phenolic compounds (24–104 mg GAE g^?1 DR), total flavonoids (4–102 mg QE g^?1g DR), total tannins (28–85 mg GAE g^?1 DR) and condensed tannins (0.62–131 mg CE g^?1 DR) were also determined. The antioxidant activities using different assays were evaluated. The predominant detected classes were the phenolic acids (42–85 %) and the flavonoids (11–48 %). The major phenolic acids were caffeic, trans‐4‐hydroxy‐3‐methoxycinnamic, p‐coumaric, and gallic acid. The predominant flavonoids were quercetin, luteolin, naringin, apigenin, and kaempferol. This study brings attention to the medicinal importance of these species as a source of oil and antioxidant molecules.     

Synthesis,Characterization, Surface,and Thermodynamic Studies of Alkyl Tetrachloroferrates: Performance Evaluation of Their Nanostructures as Biocides

Decyl and dodecylamino tetrachloroferrates were synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), elemental analysis, X-ray diffraction (XRD), nuclear magnetic resonance (¹H-NMR), and atomic absorption spectroscopy (AAS). The surface properties of the cationic surfactants including critical micelle concentration, effectiveness, minimum surface area, and maximum surface excess were determined using surface tension measurements. The effectiveness of surface tension reduction (π_cmc) was found to increase as the hydrophobic chain length increases with values of 30 and 34 mN m⁻¹ for C₁₀ and C₁₂, respectively. Moreover, the effect of temperature on micellization was determined over the range of 35–55 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) were calculated and the results indicate a spontaneous process for both micellization and adsorption. The nanoparticles (NC₁₀ and NC₁₂) of the prepared surfactants were obtained using the ball mill technique. The particle size and morphology of the nanoparticles were determined using transmission electron microscope measurements. The antibacterial study of the nanoparticle surfactants revealed their strong efficiency against fungi and different pathogenic bacteria compared with the original surfactants.     

Degradation and stabilization of cosmetic polyetherurethane in alcoholic solution

A polyetherurethane (PEU) was synthesized for potential cosmetic applications by coupling poly(tetramethylene oxide) (PTMO, M_n = 2000 g mol^?1) and poly(ethylene oxide) (PEO, M_n = 2000 g mol^?1) with 4,4′‐diphenylmethane diisocyanate (MDI), without using a chain extender. The PEU polymer, synthesized with PEO and PTMO in the ratio of 1:3 by weight, was soluble in ethanol–water mixed solvents. The solution formed a thin film in situ on the skin by coating, which was flexible and elastomeric with appropriate skin adhesiveness. However, PEU was susceptible to degradation when it was exposed to an ethanol–water (80/20 v/v %) mixed solvent and stored in an air‐filled and sealed bottle at 60°C for 4 weeks. These conditions resulted in deterioration of PEU molecular weight (M_n), viscosity, and mechanical properties. Peak analysis of the Fourier transform infrared spectrum of the aged PEU revealed that >97% of the urethane carbonyl bonds remained, whereas ether bonds were significantly reduced (～82% of initial value). The degraded PEU contained ester bonds, which were confirmed by proton and carbon‐13 nuclear magnetic resonance spectroscopy. This observation suggests that oxidative chain cleavage rather than hydrolysis was the dominant reaction in the degradation process. Two approaches were adopted to minimize oxidative degradation of PEU dissolved in an ethanol–water (80/20 v/v %) mixed solvent; they were, applying a nitrogen environment and adding an antioxidant (1.8 wt % dry PEU). The results indicate that reduction of oxidative degradation produced a synergistic effect. Vitamin E was a more effective antioxidant than butylated hydroxytoluene (BHT), which is a typical antioxidant for commercial polyurethanes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2270–2276, 2003