Azodiisobutyronitrile Research Articles

Preparation and Properties of the Polystyrene/Alumina Nanocomposites

Silane coupling agent KH-570 was applied to modify the surface capability of the alumina (Al2O3). The modified Al2O3were dispersed in styrene. The in-situ polymerization was used to prepare the polystyrene/alumina (PS/Al2O3) composites, in which azodiisobutyronitrile (AIBN) was used as initiator. FTIR, DSC and TG were applied to characterize the prepared composites. The solvent resistance, thermal resistance of the composites and the average molecular weight of PS in PS/Al2O3nanocomposites were studied. The experimental results demonstrated that the solvent resistance of PS/Al2O3nanocomposites was improved by the adding of Al2O3nanoparticles. The thermal resistance of the composites increased with the increasing of the Al2O3content. Meanwhile, the molecular weight of PS in the composites increased with the increasing of the Al2O3content.

PREPARATION OF PHOTOSENSITIVE-MONODISPERSE CORE-SHELL RASPBERRY-LIKE PSt/PAM MICROSPHERES

采用分散聚合两步加料法,在成核期后向反应体系加入光引发转移终止剂(photo-iniferter)单体2-N,N-二乙基二硫代氨基甲酰氧基乙酸-甲基丙烯酰氧基乙酯(MAEDCA)制备了核-壳单分散光敏性聚苯乙烯(PSt)微球;进一步,在甲醇介质中,利用光敏性微球在紫外光辐照下引发单体丙烯酰胺(AM)进行表面沉淀接枝聚合,制得了表面亲水、树莓状(raspberry-like)PSt/PAM微球.采用SEM及TEM观察了所得微球的结构和形貌,FTIR、UV-Vis、1H-NMR及XPS分析表明微球的photo-iniferter基团含量随MAEDCA加入量增大而提高,同时补加一定量的MAEDCA、St、AIBN、甲醇及水时所得光敏性PS微球单分散性最好;微球表面接枝PAM后变得亲水并可大量吸附Ag纳米粒子.

Syntheses of N-sulfonyl-N,N-disubstituted amidines via a three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes

A facile and efficient synthesis of N-sulfonyl-N,N-disubstituted amidines has been achieved via a CuI-catalyzed three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes in the presence of azodiisobutyronitrile (AIBN). The reaction mechanism of this reaction has also been studied.

The Film Properties of Waterborne Polyurethane Modified by Epoxidized Soybean Oil and Styrene

The waterborne polyurethane (WPU) modified by epoxidized soybean oil (ESO) and styrene (St) (WPU-ESO-St) was synthesized by free-radical emulsion polymerization using styrene (St) as a monomer, and azodiisobutyronitrile (AIBN) as initiator. The research on the mechanical properties of the film showed that with the increasing of the [NCO]/[OH] ratio, the contents of ESO, DAAM and the St, the tensile strength increased, and elongation at break decreased. The surface morphology of the film was characterized by atomic force microscopy (AFM). The glass transition temperature (Tg) of the film was characterized by differential scanning calorimetry (DSC) analysis.

Preparation, characterization of cationic terbium luminescent copolymer and its interaction with DNA

A complex of Tb3+, acrylic acid (AA), and 1, 10-phenanthroline (Phen) was synthesized. The structure and fluorescence of Tb(AA)3Phen·H2O was characterized with elemental analysis, FT-IR, and fluorescence spectroscopy. A novel copolymer containing rare earth complex, poly (METAC-co-NIPAm-co-Tb(AA)3Phen·H2O) (PMNTb), was prepared by free radical copolymerization in methanol with azodiisobutyronitrile (AIBN) as initiator. 1H NMR, fluorescence spectroscopy, UV-vis spectroscopy, and TEM were used to characterize this copolymer. The interaction of PMNTb with DNA was studied by fluorescence spectroscopy, UV-vis spectroscopy, and agarose gel electrophoresis. The results of fluorescence, UV-vis absorption, and agarose electrophoresis indicated that the PMNTb could interact with DNA in an electrostatic bonding mode and the bonding constant was 3.4 × 105 L mol−1. The TEM observation showed that the PMNTb could form micelles in water solution; the efficient complexation of PMNTb with DNA occurred. The results of in vitro cytotoxicity indicated that PMNTb had good biocompability. These results laid the foundation for the further study in potential gene detective reagent and gene delivery carrier.

Ionic-Liquid-Modified, Hybrid Silica Monolithic Column for Capillary Electrochromatography

Abstract An ionic liquid, 1-allyl-3-methyl imidazole chloride (AMIMCl), was synthesized to modify a terminal-vinyl organic-inorganic hybrid silica monolithic column by free-radical polymerization procedure using 2,2′-azodiisobutyronitrile (AIBN) as an initiator. Nucleotide monophosphates, phenols and benzoic acid compounds were successfully separated on this column under acidic conditions. The electroosmotic flow (EOF) was in the direction opposite to electrophoretic migration, and separation selectivity was apparently improved compared with an unmodified monolithic column, which can be attributed to the hydrophobic interactions on amyl chain, hydrogen bonding interactions on imidazole ring and electrostatic interactions. Repeatabilities of migration times for benzoic acid compounds were reasonable with RSD less than 4.0% for five consecutive within-column runs and 9.0%–9.8% for column-to-column measurements of three columns.

Graft Copolymerization of Starch and Acrylamide Initiated by AIBN in Aqueous Two-Phase System

In aqueous two-phase system, azodiisobutyronitrile（AIBN） was adsorbed on starch by dissolve- precipitate method. Free radical was then produced by its thermolysis, thus graft copolymerization of starch and acrylamide could be initiated. The effect of factors such as initiating system, organic solvent for AIBN dissolving, time for pre-initiation, concentration of initiator, composition and concentration of disperse system on monomer conversion, grafting efficiency, and dissolution property of the reaction product were studied. The optimum conditions of the reaction were as follows: AIBN was used as initiator and methanol as solvent; pre-initiation time was 25 min; concentration of AIBN was 2.6×10-4 mol/L; polyethylene glycol (PEG) and polyvinyl alcohol (PVA) was used as disperse system, the ratio of m(PEG):m(PVA) was 2.0:1 and their total mass fraction was 6.5%; both pre-initiation and polymerization temperatures were 60-65 °C. Monomer conversion (C) and grafting efficiency (GE) of the product obtained under these conditions were 99.4% and 99.1%, respectively.

Molecularly imprinted polymers for highly sensitive detection of morphine using surface plasmon resonance spectroscopy

Molecular imprinting technology is applied in surface plasmon resonance spectroscopy for highly sensitive and selective detection of morphine (MO). As SPR-based sensor of MO, the preparation of molecular imprinted polymer is as follows: methacrylic acids (MAA), ethylene glycol dimethacrylate (EGDMA), azodiisobutyronitrile (AIBN) were used as functional monomer, cross-linker and initiator, respectively. The experiment results showed that morphine imprinted polymer had the performance of high sensitivity and specificity, i.e. the relative signal of SPR response was proportional to the concentration of morphine in acetonitrile in the range of 10−9 mol/L to 10−6 mol/L (1 ppb–1 ppm) with LOD of 10−10 mol/L, and MO was distinguished from its analogs, such as codeine.

New cobalt-mediated radical polymerization (CMRP) of methyl methacrylate initiated by two single-component dinuclear β-diketone cobalt (II) catalysts.

Two dinuclear cobalt complexes based on bis-diketonate ligands (ligand 1: 3,3′-(1,3-phenylene)bis(1-phenylpropane-1,3-dione); ligand 2: 3,3′-(1,4-phenylene)bis(1-phenylpropane-1,3-dione)) were successfully synthesized. The two neutral catalysts all showed satisfactory activities in the cobalt-mediated radical polymerization (CMRP) of methyl methacrylate (MMA) with the common initiator of azodiisobutyronitrile (AIBN). The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities. Mono- or dicomponent low polydispersity polymers could be obtained by using the two dinuclear catalysts under proper reaction conditions. All these improvements facilitate the implementation of the acrylate CMRP and open the door to the scale-up of the syntheses and applications of the multicomponent low polydispersity polymers.

Manipulating membrane permeability and protein rejection of UV-modified polypropylene macroporous membrane

A three-step photo-induced graft polymerization of 2-hydroxylethyl acrylate (HEA) on the polypropylene macroporous membrane was carried out by using the chain transfer agent (CTA) benzyl dithiobenzoate (BDTB). Firstly, benzophenone was immobilized on the membrane surface; secondly, polyHEA (PHEA) was grafted on the membrane surface under UV irradiation in the presence of HEA and BDTB; thirdly, the PHEA grafted membranes with and without CTA moieties were respectively immersed in a thermostated water bath at 55 °C for the further grafting polymerization of HEA; in this step, PHEA was also grafted on the second-step modified membrane, with the grafted membrane containing CTA moieties served as macro-CTA and azodiisobutyronitrile (AIBN) as initiator. The degree of grafting (DG) of PHEA increased with UV irradiation time in the first step. In the second step, DG increased with UV irradiation time and monomer concentration, and with the decrease of CTA concentration. In the third step, DG continuously increased with reaction time under thermostated conditions without adding the free radical initiator; for the PHEA grafted membranes with CTA moieties on the grafting chain, DG was relatively higher than that for the PHEA grafted membranes without CTA moieties; also PHEA was grafted on the membrane surface by using the second-step modified membrane as the macro-CTA and AIBN as initiator, DG continued to increase with the reaction time. The pure water flux increased with the rise of DG up to 4.48 wt.%, then it decreased gradually, which shared the same trend with the water flux during the filtration of protein dispersion. The flux recovery ratio after water cleaning also increased with the rise of DG. But the rejection of protein dispersion followed the reversed trend of the pure water flux: it decreased down to 4.48 wt.% then increased with the rise of DG.

Fatty acid composition of Oenothera biennis seed oil during storage. Antioxidant activity

In continuation of research on the lipid composition of seed oil from Oenothera biennis growing in Krasnodar Territory [1], we studied the effect of long-term (12 months) storage on the content of the principal fatty acids palmitic (16:0), stearic (18:0), oleic (18:1), linoleic (18:2), and -linolenic (18:3). An oil sample from Oenothera biennis seeds (~1 mL) was placed in a tube (~2 mL), closed with a stopper, and stored in a refrigerator at 8°C. A sample was taken each month. The fatty acid composition was determined (Table 1). The composition and content of fatty acids in the samples were practically constant and within the uncertainty limits of the experiment. The presence or absence of oxidized lipids was determined by hydrolyzing a sample of oil that was stored for one year, isolating the fatty acids, and preparing the methyl esters, which were analyzed for the presence of oxidized fatty acids by analytical TLC (ATLC) using solvents 1–3. The models were methyl esters of fatty acids from castor oil that contained monohydroxyand dihydroxy-fatty acids. However, spots corresponding to oxidized fatty acids were not observed in the studied sample. Oil of O. biennis is known to contain tocopherols [2, 3], which we identified previously in the neutral lipids [1]. GC/MS of the unsaponified fraction of O. biennis oil identified the natural antioxidants -, -, and -tocopherol from their mass spectra using the AMDIS software [4]. The antioxidant activity of the oil was analyzed using a model system based on radical-chain oxidation of methyloleate initiated by azodiisobutyronitrile (AIBN). The advantage of this model system is that the oxidation process in it is very similar to the lipid oxidation process in living systems. Studies of natural compounds using this system and analogous apparatus are rather rare. Figure 1 shows typical kinetic curves for oxygen absorption during initiated oxidation of methyloleate without an inhibitor and with O. biennis seed oil. It can be seen from the curves that the reaction occurred with an induction period. The rate of uninhibited oxidation of methyloleate and the oxidation rate of methyloleate inhibited by the oil components after complete consumption of the inhibitor were the same. Therefore, our experimental conditions did not reveal the contribution from oxidation of the oil itself. The reduced oxidation rate in the initial portion (induction period) indicated that an additional pathway for consumption of peroxide radicals had opened.

Effect of graft copolymerization of fir sawdust lignocellulose with N-vinylpyrrolidone on adsorption capacity to tea catechins

Abstract Fir sawdust lignocellulose (FSL) adsorbent was copolymerized with N-vinylpyrrolidone (NVP) in four solvent systems so as to improve its adsorption capacity to tea catechins. It showed that the improvement of adsorption capacity to total catechins was influenced by the reaction solvent, ratio of azodiisobutyronitrile (AIBN) to NVP, ratio of NVP to FSL, reaction temperature and time. The optimum graft copolymerization conditions were: acetonitrile as reaction solvent, AIBN/NVP 0.04, NVP/FSL 0.2 at 70 °C for 6 h. Scanning electron microscopy revealed that the grafted-on NVP was deposited on the FSL surface and in the intercellular regions of the grafted FSL. Fourier transforms infrared spectrum showed that the FSL absorption band at 1634.87 cm −1 induced by –C O was shifted to around 1660 cm −1 and the absorption band was greatly strengthened after NVP grafting.

Synthesis and Properties of Amphiphilic Photosensitive Telechelic Polymer C-PNIPAAm

Coumarin-containing disulfide(C-S-S-C) was designed and synthesized,which could be used as chain transfer agent with tributylphosphine and water.With N-isopropyl acrylamide(NIPAAm) as monomer and azodiiso-butyronitrile(AIBN) as initiator,an amphiphilic photosensitive telechelic polymer(C-PNIPAAm) was synthesized.The polymer was characterized by Fourier transform infrared(FT-IR) spectroscopy,gel permeation chromatography(GPC) and proton nuclear magnetic resonance spectroscopy(1H-NMR).We found that the polymer can form micelles in water itself with fluorescein as a hydrophobic agent.When irradiated by UV light(λ310 nm),the coumarin unit at the end of the polymer chain was photodimerized,which changed the micelle structure and hydrophobic fluorescein was effectively released to the water.Dynamic laser scattering(DLS) showed that the average diameter of the micelles increased from 56.6 nm to 101.0 nm after irradiation.

Preparation of carboxylic magnetic polymeric composite particles by miniemulsion polymerization in the absence of hydrophobe

Carboxylic magnetic polymeric composite particles (C-MPCPs) were prepared by miniemulsion polymerization in the absence of hydrophobe using styrene (St) as monomer, methacrylic acid (MAA) as comonomer, sodium dodecyl sulfate (SDS) as emulsifier, and azodiisobutyronitrile (AIBN) as initiator in the presence of hydrophobic magnetite particles. For comparison, non-carboxylic magnetic polymeric composite particles (N-MPCPs) were also prepared under the same conditions as C-MPCPs but without MAA as comonomer. Microscopic morphology of resulting C-MPCPs and N-MPCPs was observed by Transmission Electron Microscopy (TEM). Magnetic properties of C-MPCPs in dry condition were investigated by vibrating sample magnetometer (VSM). The results showed that the encapsulation of magnetite to prepare C-MPCPs by miniemulsion in the absence of hydrophobe was successful but not totally successful in the preparation of N-MPCPs, and the resultant C-MPCPs exhibited a broad practical size distribution, superparamagnetism and a certain level of magnetic response. The mechanism of miniemulsion polymerization to encapsulate magnetite particles successfully in the absence of hydrophobes was hypothesized that the hydrophobic magnetite particles could act as a hydrophobe and MAA could enhance the hydrophobicity of magnetite particles by ensuring oleic acid adsorption on magnetite particles' surface in acid form instead of salt form.

Synthesis of Novel Porphyrin and its Complexes Covalently Linked to Multi-Walled Carbon Nanotubes and Study of their Spectroscopy

Novel covalent porphyrin and its complexes (Co2+, Zn2+) functionalized multi-walled carbon nanotubes (MWNTs) have been successfully synthesized by the reaction of the carboxyl on the surface of MWNTs which was synthesized to use carbon radicals generated by the thermal decomposition of azodiisobutyronitrile (AIBN) with 5-p-hydroxyphenyl-10,15,20-triphenyl-porphyrin and its complexes (Co2+, Zn2+). Three resulting nanohybrids were characterized by spectroscopy (FT-IR, Raman, and UV-vis), TGA, and TEM. The quality of porphyrin attached to the MWNTs was determined from thermogravimeric analysis (TGA) of the MWNTs, which showed a weight loss of about 60%. The Raman and absorption spectroscopy data showed that the electronic properties of modified MWNTs were mostly retained, without damaging their one-dimensional electronic properties. From fluorescence measurements, it was observed that the porphyrin and its complexes (Co2+, Zn2+) were nearly quenched by MWNTs, indicating that this covalently modified mode facilitated the effective energy or electron transfer between the excited porphyrin moiety and the extended π-system of MWNTs.

Comparative Analysis of Quercetin Oxidation by Electrochemical, Enzymatic, Autoxidation, and Free Radical Generation Techniques: A Mechanistic Study

Quercetin, the most abundant flavonoid in dietary fruits and vegetables, acts as antioxidant or prooxidant depending on the environmental conditions. The antioxidant behavior is believed to involve initial oxidative steps with subsequent changes in the flavonoid skeleton, which ultimately alters the chemical and biological properties of these molecules. Although the mechanism is still unclear, it has been suggested to be strongly influenced by the surrounding media. This paper reports the oxidation of quercetin by air oxygen or autoxidation, bulk electrolysis, mushroom tyrosinase, and azodiisobutyronitrile (AIBN). The central aim of this study is to systematically examine how the similarities and differences of quercetin transformation can be affected by the nature of the oxidation systems. Using a range of molecular and structural characterization techniques (UV-vis, LC-MS, GC-MS, and NMR), the oxidation of quercetin was found to result in the generation of somewhat similar metabolites including depside, phenolic acids, and quercetin-solvent adducts, although the transformation process and quantities of each product depend on the type of oxidation method employed. The rate of quercetin autoxidation can be fitted to a monoexponential first-order decay with a k value of 6.45 x 10(-2) M(-1) s(-1). Comparison of quercetin oxidative products in the different systems provides a deeper insight into the underlying mechanism involved in the oxidation process. This work demonstrates that the presence of water and/or nucleophiles as well as different catalysts (tyrosinase, AIBN, or air oxygen in solution) may have very important implications for the formation of quinone with subsequent oxidative cleavage or polymerization. Moreover, the apparent first-order kinetics of autoxidation can indicate a rate-determining, one-electron oxidation of quercetin anions followed by two fast steps of radical disproportionation and solvent addition on the resulting quinone.

Synthesis of liquid crystalline moiety containing N‐cyclohexylmaleimide copolymers

AbstractAtom transfer radical polymerization (ATRP) was applied to copolymerize liquid crystalline acrylate (6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate) (LC6) monomer and N‐cyclohexylmaleimide (NCMI) monomer. Copolymerization of LC6 and NCMI in the presence of Cu(I)Br/N, N, N′, N′′, N′′‐pentamethyldiethylene‐triamine (PMDETA) catalyst system using anisole as a solvent at 110°C initiated by 2‐bromopropionyl bromide afforded well‐defined copolymers. In addition, free radical polymerization (FRP) was applied using 2,2′‐azodiisobutyronitrile (AIBN) as an initiator in toluene at 70°C for the same monomers. The influences of several factors such as monomer ratio and time on the copolymerization, spectral, and thermal properties of resultant copolymers were investigated. The glass transition temperature and thermal stabilities of the copolymers were increased by increasing the N‐substituted maleimide (N‐cyclohexylmaleimide) content. As a result, thermally stable liquid crystalline alternating copolymers were synthesized by introducing maleimide segments into the polymer. Copyright © 2008 John Wiley & Sons, Ltd.

One-step copolymerization modified magnetic nanoparticles via surface chain transfer free radical polymerization

Copolymer brushes growing onto magnetic nanoparticles were prepared by surface chain transfer free radical polymerization. Block copolymer brushes (P(PEGMA)- co-PNIPAAm) consist of poly(ethylene glycol) monomethacrylate (PEGMA) and N-isopropylacrylamide monomer. X-ray photoelectron spectroscopy (XPS) characterized the chemical composition of copolymer. Thermogravimetric analysis (TGA) suggested that the amount of copolymer on magnetic nanoparticles decreased with increasing azodiisobutyronitrile (AIBN). The saturation magnetization decreased significantly with increasing P(PEGMA)- co-PNIPAAm. The thermosensitive point is about 43 °C for magnetic nanoparticles with 33.8% P(PEGMA)- co-PNIPAAm.

Novel azo-peresters radical initiators used for the synthesis of acrylic pressure-sensitive adhesives

Acrylic pressure-sensitive adhesives (PSA) based on two monomers: 2-ethylhexyl acrylate and acrylic acid were synthesized in organic solvent ethyl acetate using AIBN (2, 2'-azo-diisobutyronitrile) and new synthesized azo-peresters as radical initiators. After polymerization the viscosity, molecular weight and polydispersity of synthesized acrylic PSA were evaluated. The novel synthesized radical azo-perester initiators were synthesized, isolated and compared with industrial predominant usable azo-initiator AIBN.

Self-Stabilized Magnetic Polymeric Composite Nanoparticles by Emulsifier-Free Miniemulsion Polymerization

Self-stabilized magnetic polymeric composite nanoparticles (SS-MPCPs) were prepared by emulsifier-free miniemulsion polymerization using styrene (St) as a monomer, sodium p-styrenesulfonate (NaSS) as an ionic comonomer, hexadecane (HD) as a hydrophobe, and 2,2'-azodiisobutyronitrile (AIBN) as an initiator in the presence of hydrophobic magnetite particles. The hydrophobic magnetite particles with an average size of about 10 nm were prepared by the acidification of the water-based magnetite ferrofluid, previously synthesized by a chemical coprecipitation method. Some colloidal features of the synthesized SS-MPCPs were analyzed. The morphology and the particle size distributions (PSDs) of the SS-MPCPs were observed and analyzed by transmission electron microscopy (TEM). The surface charge density was determined by conductometric titration. The surface hairy layer and the colloidal stability of SS-MPCPs against different electrolytes were determined by photon correlation spectroscopy (PCS). The average Fe3O4 content of SS-MPCPs was determined by thermogravimetric analysis (TGA). Vibrating sample magnetometry (VSM) was used to analyze the magnetic properties of the SS-MPCPs under dry conditions. The results show that the encapsulation of magnetite is successful and the distribution of magnetite particles inside SS-MPCPs is mainly in the core of the particles. The best SS-MPCPs prepared had a relatively narrow PSD, exhibited superparamagnetism, and possessed some magnetic response.