Azodiisobutyronitrile Research Articles

A selective resonance Rayleigh scattering method for determination of iodine by graphene oxide surface molecularly imprinted polyacrylamide probe

A new graphene oxide nanosurface molecularly imprinted polymer (GO@MIP) probe was synthesized by microwave irradiation, using graphene oxide (GO) as the carrier, iodine as the template molecule, acrylamide as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, azodiisobutyronitrile (AIBN) as the initiator, and acetonitrile as the pore forming agent. The nanoprobe recognizes the iodine, and exhibits significant resonance Rayleigh scattering energy transfer (RRS-ET) effect between iodine as the acceptor and the nanoprobe as donor. When iodine concentration was in the linear range of 0.02–0.5 mmol/L, the decreased RRS intensity was linear to the concentration. And it was used for the determination of iodine in water samples and iodate ions in salt samples.

Controllable synthesis, characterization, and evaluation of poly (lauryl methacrylate-soybean oil) as a lubricant additive

Traditional free radical polymerization has poor controllability, and traditional petroleum-based lubricant additives have adverse effects on the environment. Poly (lauryl methacrylate (LMA)-soybean oil (SBO)) (P(LMA-SBO) was synthesized using Salen-Cu(II) complex as a catalyst and azodiisobutyronitrile (AIBN) as an initiator by the Schlenk techniques. The structure of P(LMA-SBO) was characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) followed by evaluating the solidification point depression performance by the Chinese standard method GB/T 510-2018, and the wax crystal morphology was studied by optical microscopy. The results show the catalytic activity could be 22.88 × 104 g·mol−1·h−1 and the number average molecular weight (M n) of the copolymer is 8.71 × 104 with a low dispersity (Ɖ) of 1.37 under the optimal conditions, which indicates good controllability of the polymerization. Adding 1.0%(w) P(LMA-SBO) to the lubricating oil fraction (350–500 °C) could reduce the solidification point by 15 °C. Therefore, the Salen-Cu (II) catalyst was successfully applied to the controlled polymerization of LMA and SBO. The vegetable oil-based solidification point depressant of P(LMA-SBO) could be used as a potential alternative to replace the traditional solidification point depressant in the future.

A new surface molecularly imprinted polyacrylamide nanoprobe for trace Cr(VI) with RRS technique

This article was used potassium dichromate as the template molecule, silver nanoclusters as the nano matrix, acrylamide as the monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, and azodiisobutyronitrile (AIBN) as the initiator to prepare a new silver nanocluster surface MIP (AgNCs@MIP) nanoprobe for chromate. Upon addition of Cr(VI), it selectively adsorbs on the surface of AgNCs@MIP nanoprobes. The dichromate ion absorption peak at 350 nm overlaps with the AgNCs@MIP RRS peak at 370 nm, resulting in strong RRS energy transfer (RRS-ET) and a decrease in the RRS intensity. The decreased RRS intensity is directly proportional to the concentration of dichromate ions in the range of 0.0025–0.015 µmol/L, with a detection limit of 0.8 nmol/L. Therefore, a simple, fast, sensitive and selective RRS method for the determination of trace Cr(VI) in mineral water has been established, with a relative standard deviation of 9.2–9.8 % and recovery of 95.20 %—103.60 %.

Facile in situ polymerization synthesis of poly(ionic liquid)-based polymer electrolyte for high-performance solid-state batteries

The rational one-step design of poly(ionic liquid) solid polymer electrolyte (PIL-SPE) with outstanding ionic conductivity and inferior interfacial resistance with Li-electrode to preclude the Li-dendrite growth and interfacial instability of solid-state lithium metal batteries (ASLMBs) remains a grand challenge. Herein, we provide a s facile, one-step, and productive approach for the synthesis of PIL-SPE via the in situ polymerization of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfony)imide ([VBIm][TFSI]) in the presence of bis(trifluoromethane) sulfonamide lithium salt (LiTFSI) using azodiisobutyronitrile (AIBN) as initiator. This approach endows a compact and compatible interface between Li-electrode and PIL-SPE with an excellent ionic conductivity that depends on the Li-salt concentration. Thereby, in situ polymerization of monomer with 40 wt% LiTFSI (PIL-SPE-LiTFSI-40) revealed the highest ionic conductivity of 1.35 × 10-3 S cm−1 at 303 K and 6.16 × 10-3 S cm−1 at 353 K, besides excellent lithium transference number (0.54), oxidative stability up to 5.3 V, and constant current plating/stripping cycles for 1000 h at 0.15 mA cm−2. Meanwhile, ASLMBs composed of PIL-SPE with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes delivered discharge capacities of 164.3 mA h g−1 and 155.3 mA h g−1 at 0.1 C, respectively, along with 92 % capacity retention after 100 cycles. This study may revolutionize the synthesis of PIL-SPE electrolytes for the next generation of efficient and durable ASLMBs.

In situ polymerized ionic liquids in polyester fiber composite membranes for detection of trace oil

In situ trace detection on ultra-clean surfaces is an important technology. The polyester fiber (PF) was introduced to serve as the template, to which the ionic liquids were bonded by hydrogen bonding. Polymerized ionic liquids (PIL) in PF were formed by in situ polymerization with the azodiisobutyronitrile (AIBN) and IL. The trace oil on metal surfaces was enriched by the composite membrane based on similar compatibility principle. The absolute recovery of the trace oil ranged from 91%-99% using this composite membrane. In the extraction samples, desirable linear correlations were obtained for trace oil in the range of 1.25-20mg/mL. It has been proven that a 1cm2 PIL-PF composite membrane can effectively extract as little as 1mg of lubricating oil on an ultra-clean metal surface of 0.1m2 with the LOD of 0.9mg/mL, making it a promising material for in situ detection of trace oil on metal surfaces.

Probe into effect of the initiator on the thermal runaway hazards of methyl methacrylate bulk polymerization

The bulk polymerization of methyl methacrylate (MMA) is of great importance in chemical industry, but the polymerization process is highly hazardous, and few reports have focused on the effect of initiators on its thermal hazards. In this work, to thoroughly explore the thermal hazard characteristics, the runaway behavior of MMA bulk polymerization is investigated by a combination of thermodynamics experimental and kinetics theoretical methods. The results indicate that the presence of initiator exhibits an undesirable thermal hazard to the MMA bulk polymerization, and its exothermic behavior is also greatly influenced by the type and concentration of initiator. For azobisisoheptanenitrile (ABVN), azodiisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO) initiators as examples, the AIBN-initiated reaction has the shortest adiabatic induction period (39.51 min), whereas the BPO-initiated polymerization exhibits the strongest maximum temperature-rising rate and maximum pressure-rising rate. Under adiabatic runaway, the temperature and pressure change significantly with increasing AIBN concentration, revealing a great potential risk of thermal runaway. Kinetic parameters are calculated to further understand the thermal runaway mechanisms, showing a strong agreement with the adiabatic experimental data. Finally, based on the cooling failure scenario, severity grading is determined by the evaluation criteria. The current work provides extensive data as a reference and guidance for the process design and optimization of MMA bulk polymerization from the perspective of safety.

Synthesis and characterization of UV curable biocompatible hydrophilic copolymers containing siloxane units

Tissues are highly three-dimensional structure complexes composed of different cell types and their interactions. One of the main challenges in tissue engineering is the inability to produce large, highly perfused scaffolds in which cells can grow at a high cell density and viability. Poly(dimethyl siloxane) (PDMS) is used as a flexible, biocompatible cell culture substrate with tunable mechanical properties. However, its fragility and hydrophobicity still pose a challenge. Here, we present a new strategy for the three-step one-pot synthesis of novel biocompatible hydrophilic copolymers containing siloxane units. In the first step, free radical copolymerization of acrylic acid (AA), butyl methacrylate (BMA), and 2-hydroxyethyl methacrylate (HEMA) was carried out in dioxane (DO) solution in the presence of 2,2′-azodiisobutyronitrile (AIBN). In the second step, the copolymers were modified with diepoxypropoxypropyl-terminated polydimethylsiloxane (DE-PDMS), and in the third step, the copolymers were additionally modified with glycidyl methacrylate (GMA). The modified copolymers were characterized by FTIR, NMR spectroscopy and elemental analysis. Films of modified copolymers were prepared by UV curing. SEM studies revealed microphase separated morphology with distribution of PDMS domains. The mechanical properties of the films depended on the amount of incorporated silicone modifier. The films were more hydrophilic than PDMS films. All novel copolymers showed high biocompatibility.

ANTIOXIDANT PROPERTIES OF LEAVES OF SOME TREES

ANTIOXIDANT PROPERTIES OF LEAVES OF SOME TREES

Process hazard evaluation and thermal runaway prediction for styrene polymerization initiated by peroxide-azo composites

Styrene is an important monomer for synthetic resins, ion exchange resins and synthetic rubber. Styrene polymerization requires the use of initiators to increase the reaction rate, with composite initiators showing promise for increased reaction rates. However, increased reaction rates in polymerization, if uncontrolled, can lead to thermal runaway with disastrous consequences. Numerous runaway incidents have been documented, indicating inadequate awareness of the thermal hazards of polymerization reactions. This study focuses on determining via calorimetric techniques the thermal hazards of styrene polymerization using azodiisobutyronitrile (AIBN) and tert-Butyl peroxybenzoate (TBPB) composite initiators. Differential scanning calorimetry (DSC) is employed to investigate the thermal decomposition properties of composite initiators with varying composition. Non-isothermal experiments and adiabatic experiments are used to determine the thermal hazard parameters including initial exothermic temperature and heat release of styrene polymerization. The risk of secondary reactions is evaluated by reaction calorimetry (RC1e) and product thermogravimetric analysis (TGA). Key safety parameters of the exothermic reaction, such as the onset temperature, heat release, time to maximum rate under adiabatic condition as well as activation energy, are presented. The results show that the thermal hazard of the polymerization reaction is lowest when the ratio of AIBN to TPPB in the composite initiator is 1:1. In this scenario, the temperature reached by the uncontrolled reaction does not provoke the decomposition of the products, yet the runaway consequences are still unacceptable. This work provides extensive data as a reference for the process optimization of styrene polymerization from the perspective of safety.

N-hydroxyphthalimide anchored on hexagonal boron nitride as a metal-free heterogeneous catalyst for deep oxidative desulfurization

A metal-free N-hydroxyphthalimide/hexagonal boron nitride (NHPI/h-BN) catalytic system was developed for deep oxidative desulfurization (ODS) of fuel oils. Detailed experiments find that the heterogenization process of loading NHPI on h-BN not only benefits to the dispersion and utilization of NHPI, but also can significantly promote the catalytic performance. By employing NHPI/h-BN as the catalyst, azodiisobutyronitrile (AIBN) as the metal-free initiator, a 95% conversion of dibenzothiophene (DBT) can be acquired under the reaction conditions of 120 °C and atmospheric pressure with molecular oxygen (O2) as oxidant. Moreover, the heterogenization is convenient for the regeneration of the catalyst with >94% DBT conversion after being recycled seven times. Characterizations illustrate that the promoted catalytic activity along with the regenerability originate from the interactions between NHPI and h-BN. The catalytic mechanism study shows that molecular oxygen is readily activated by the NHPI/h-BN to form a superoxide radical (O2•−), which oxidize DBT to DBTO2 for desulfurization.

Mechanisms of Ssp3–H functionalization of thiolacetic acid: A density functional theory investigation

AbstractMechanisms for Ssp3–H functionalization of thiolacetic acid, initiated by AIBN, have been investigated by M06‐2X‐D3/ma‐def2‐TZVP method and basis set, and SMD model was employed to simulate the solvent effect of toluene. The computational results suggest that azodiisobutyronitrile (AIBN), as the radical initiator, would have an intramolecular homolytic reaction; then Ssp3–H activation of thiolacetic acid could be finished via two possible paths; the obtained thiyl radical and diyne would go through electrophilic reaction, ring‐closure reaction, and SN2 reaction to yield 3,4‐fused‐ring‐substituted thiophenes. While in the second part, the mechanism of side reaction has also been investigated, revealing that main reaction has a lower energy barrier. Localized orbital locator isosurfaces and electron spin density isosurface graphs can analyze the structures and reveal the substances.

Roles of Proton in the Formation of Particles: Soap‐free Emulsion Polymerization of Styrene using AIBN and Potassium Persulfate as Initiators

AbstractIn this paper, the hydrophobic effect or hydration of hydrophobe was firstly introduced into the mechanism of polystyrene particles formation. Negatively charged surface of hydration shell was proposed due to the ordered structure of water molecules. Consequentially the concentration of hydrophobic chains depended on pH because protons destroyed the hydration shell, thereby extruded hydrophobic chains from the H‐bonds networks. The soap‐free emulsion polymerization of styrene by using AIBN (azodiisobutyronitrile) and KPS (Potassium Persulfate), respectively was performed at various pHs. It was proved that protons played a crucial role on the formation of PSt (polystyrene) particles. By using AIBN, particles were not prepared at pH 2.0 (HAc), pH 4.0 (HCl) and pH 2.0 (HCl), whereas by using KPS, particles were obtained regardless to pH. It indicated that anions of sulfate greatly enhanced the tolerance of hydration shell to the suffering from protons. Meanwhile, the roles of polymerization in the monomer phase, aqueous phase and growing particles were elucidated. By using AIBN, ca. 30 % PSt with Mn (Numeral average molecular weight) =300‐1500 formed in the monomer phase at pH 6.8, which dissolved in water at pH 8.0 and pH 10.0. By using KPS, ca. 20 % and 30 % conversion of St were found in the aqueous phase at pH 2.0 (HCl) and pH 10.0 (NaOH), respectively. At pH 2.0 (HCl), oligomers generated in the aqueous phase were protonated, whereas at pH 10.0 (NaOH), they were soluble due to the seriously suppressed dissociation of water. At other pHs, oligomers captured protons, thereby relieved particles and interface from the suffering of protons. As the concentration of oligomers increased, oligomers precipitated to form clusters due to the increase of average number of protons on the surface of oligomers hydration shell, which successively incorporated into the growing particles, thus enlarged PDI (Polydispersity index) of MW (Weight‐average molecular weight) distribution in particles. By using AIBN, owing to the limited partition of AIBN in the interfacial layer of St phase, the flat‐roof peaks of GPC curves were observed, namely that the weight fraction of Mi was constant. It implies that the free‐radicals are living in the growing particles.

Stereocomplexation of Poly(Lactic acid) and Chemical Crosslinking of Ethylene Glycol Dimethacrylate (EGDMA) Double-Crosslinked Temperature/pH Dual Responsive Hydrogels.

Physical crosslinking and chemical crosslinking were used to further improve the mechanical properties and stability of the gel. A temperature/pH dual sensitive and double-crosslinked gel was prepared by the stereo-complex of HEMA-PLLA20 and HEMA-PDLA20 as a physical crosslinking agent, ethylene glycol dimethacrylate (EGDMA) as a chemical crosslinking agent, and azodiisobutyronitrile (AIBN) as an initiator for free radical polymerization. This paper focused on the performance comparison of chemical crosslinked gel, a physical crosslinked gel, and a dual crosslinked gel. The water absorption, temperature, and pH sensitivity of the three hydrogels were studied by a scanning electron microscope (SEM) and swelling performance research. We used a thermal analysis system (TGA) and dynamic viscoelastic spectrometer to study thermal properties and mechanical properties of these gels. Lastly, the in vitro drug release behavior of double-crosslinked hydrogel loaded with doxorubicin under different conditions was studied. The results show that the double-crosslinked and temperature/pH dual responsive hydrogels has great mechanical properties and good stability.

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Summary Carboxylation of terminal alkynes with CO2 via direct C–H bond activation is a highly appealing way to capture and convert CO2 but faces great challenges and difficulty. Here, we report an efficient catalyst that is prepared simply through introduction of p-tert-butylaniline into graphite oxide powders followed by localized growth of Ag nanoparticles (NPs). The bulky nature of p-tert-butylaniline facilitates the powder exfoliation, giving rise to mass production of uniform modified graphene oxide (tert-GO) nanosheets of 4 nm in thickness. Notably, Ag/tert-GO shows excellent catalytic activity for converting alkynes regardless of containing electron-donating or electron-withdrawing groups under mild reaction conditions. The synergy of the amide linkages on tert-GO nanosheets and the supported small-sized Ag NPs is recognized as the vital role in promoting adsorption of CO2 and subsequent conversion.

Study on a Biomimetic Enzyme-Linked Immunosorbent Assay for Rapid Detection of Flumequine in Animal Foods

Flumequine (FLU) is widely used as an antibiotic in the treatment and control of animal diseases, which may result in the presence of residues harmful to humans in food products of animal origin. A novel and fast biomimetic enzyme-linked immunosorbent assay (BELISA) was developed for the determination of FLU based on a molecularly imprinted polymer (MIP) as a selective affinity agent. With an optimized molar ratio of FLU to methacrylic acid (MAA) of 1:2 determined by molecular dynamic simulations, the MIP was directly synthesized on the surface of a 96-well plate (as solid support) with FLU as the template molecule, MAA as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and azodiisobutyronitrile (AIBN) as the initiator. Under the optimized conditions, the BELISA method was established with a sensitivity (IC50) of 0.141 μg/mL and a detection limit (IC15) of 1.09 × 10−3 μg/mL. The developed method was applied to determine FLU concentrations in spiked beef and shrimp samples, with satisfactory recovery values ranging from 80.7 to 92.2% with relative standard deviations (n = 3) between 3.3% and 7.0%. This method can be used for the rapid determination of FLU in animal foods and has promising applications in food safety monitoring.

Controlled RAFT polymerization of MMA in confined space of various pore sizes of SBA-15

A series of mesoporous SBA-15 with various pore diameter (8, 15, 22 and 27 nm) were synthesized and used as “microreactor”. Reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) was conducted in the channels of SBA-15 using azodiisobutyronitrile (AIBN) as initiator, ethyl xanthate ethyl propionate as chain transfer agent. The obtained PMMA/SBA-15 composites and neat PMMAs from composites were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption and desorption, Fourier transform infrared spectroscopy, thermogravimetry analysis, differential scanning calorimetry, hydrogen nuclear magnetic resonance. Results showed that compared with PMMA from conventional RAFT polymerization, PMMAs obtained from internal SBA-15 featured with narrower molecule weight distribution (1.34–1.55) and higher thermal stability due to confinement effects. With the increment of pore size of SBA-15, the molecular weight and glass transition temperature (Tg) of PMMA obtained from internal SBA-15 were distinctly improved whereas isotacticity of the PMMA decreased. The properties of the PMMA were managed with controllable RAFT polymerization by regulation the pore size of SBA-15.

Synthesis of (E)-vinyl Isobutyronitriles via Fe(III)-catalyzed Decarboxylative Cross-coupling of Cinnamic Acids and AIBN under Additive-free Conditions

A facile, efficient, additive-free and eco-friendly protocol for the synthesis of (E)-vinyl isobutyronitriles via Fe(III)-catalyzed decarboxylative cross-coupling of cinnamic acids and AIBN (azodiisobutyronitrile) has been developed. The presented methodology offers several advantages such as easy accessibility and stability of substrates, inexpensive catalyst and simple post-treatment procedure.

Triphenylphosphine-Containing Thermo-Responsive Copolymers: Synthesis, Characterization and Catalysis Application

Triphenylphosphine-containing thermo-responsive copolymers of 4-(diphenylphosphino) styrene (DPPS), di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethylene glycol) methyl ether methacrylate (average molecule weight is 300, OEGMA300) were synthesized by free-radical copolymerization using azodiisobutyronitrile (AIBN) as an initiator in solution polymerization. A series of copolymers P(DEGMA-co-DPPS-co-OEGMA300) with different lower critical solution temperature (LCST) were synthesized. The synthesized copolymers were well characterized by 1H NMR, 31P NMR and gel permeation chromatography (GPC). Based on the copolymers, a thermo-responsive and water soluble assembled catalyst of palladium acetate was developed. In the presence of the thermo-responsive copolymer-supported palladium catalyst, the Suzuki-Miyaura reaction proceeded efficiently in water. The catalyst was reused at least five cycles without obvious decrease in catalytic activity and can be easily recovered by heating/centrifugation of the polymer aqueous solution.

Synthesis of zinc(II) complex-containing thermo-responsive copolymer based on activated ester functionalization and its catalysis application

In this study, we report the synthesis of pybox zinc(II) complex-containing thermo-responsive copolymer through activated ester strategy and their application in Knoevenagel condensation as an efficient and recoverable catalyst. First, a series of thermo-responsive copolymers P(MASI-co-DEGMMA-co-OEGMMA300) of activated ester monomer N-methacryloxysuccinimide (MASI), ethylene glycol methyl ether methacrylate (DEGMMA) and oligo(ethylene glycol) methacrylate (OEGMMA300) were synthesized through free-radical copolymerization using azodiisobutyronitrile (AIBN) as an initiator in solution polymerization. The lower critical solution temperature (LCST) of the P(MASI-co-DEGMMA-co-OEGMMA300) copolymers was controlled by adjusting the mole fractions of the monomers. The synthesized copolymers were well characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), infrared spectrum (FTIR) and gel permeation chromatography (GPC). Then, pybox ligand with a terminal amino group was introduced into P(MASI-co-DEGMMA-co-OEGMMA300) based on activated ester functionalization, and further coordinate with ZnCl2 to afford a pybox zinc(II) complex-containing thermo-responsive copolymer. The zinc complex-containing polymer displayed excellent catalytic activities for Knoevenagel condensation reaction in water at room temperature, and it can be easily recovered by centrifugation at a higher temperature, above the LCST of the copolymer after reaction. The recovered catalyst can be reused at least five cycles without obvious decrease in catalytic activity.

TBHP/AIBN-Mediated Synthesis of 2-Amino-thioazoles from Active Methylene Ketones and Thiourea under Metal-free Conditions

A new oxidative system of tert-butyl hydroperoxide (TBHP)/azodiisobutyronitrile (AIBN) has been used for the first time for a convenient, metal-free synthesis of substituted 2-aminothioazoles from active methylene ketone derivatives and thiourea. The reaction is postulated to proceed via an oxidative cyclization initiated by a radical process and followed by a condensation reaction.