Azobisisobutyronitrile Concentration Research Articles

Dual-responsive silicone films loaded with silver particles for potential biomedical applications

Silicone is one of the most widely used polymers in biomedicine because of its versatile use in medical products; it can be modified to improve their properties with potential use in biomedicine. In this research, silicone films were modified by a one-step grafting reaction of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) initiated by azobisisobutyronitrile (AIBN) and gamma radiation from a Co-60 source. Variables such as temperature, solvent, reaction time, monomer concentration, dose, and amount of AIBN were studied to determine its influence on the graft. The modified films were characterized by infrared spectroscopy (FTIR-ATR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM-EDS), mechanical tests, and physicochemical studies to determine critical pH and Lower Critical Solution Temperature (LCST). Given the incorporation of the monomers, the synthesis and loading of Ag particles was carried out, through a reaction in water without reducing agents. Finally, the antimicrobial activity of the films synthesized by both methods and loaded with silver was evaluated against S. aureus and E. coli bacteria confirming their in vitro effectiveness.Silicone, acrylic acid, N-isopropylacrylamide, grafting, gamma radiation, silver particles.

"A NOVEL RICE STRAW–BUTYL ACRYLATE GRAFT COPOLYMER: SYNTHESIS AND ADSORPTION STUDY FOR OIL SPILL CLEANUP FROM SEAWATER "

For the first time, a potential material for oil spill cleanup has been successfully synthesized by the graft polymerization of butyl acrylate (BA) onto rice straw (RS) using 2,2'-azobisisobutyronitrile (AIBN) as initiator and divinyl benzene (DVB) as cross-linking agent. The copolymer synthesis was controlled by the concentration of monomer BA and AIBN, reaction time, and temperature. It was found that the optimal conditions for the highest graft yield of 41.50% were as follows: [AIBN] = 0.04 mol/L, [BA] = 1.50 mol/L, 180 min at 75 °C. The graft copolymer RS-g-BA was structurally analyzed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). In the presence of DVB (1.5%), the maximal adsorption capacity of the copolymer was 20.56 g/g. The reusability of the RS-g-BA copolymer was assessed during seven sorption/desorption cycles with 70% recovery. The experimental data were clearly more suitably fitted by the Langmuir monolayer adsorption model rather than by the Freundlich isotherm model. The kinetic study indicated that oil adsorption by RS-g-BA is likely to be a chemisorption process.

Synthesis of cellulose-g-poly(acrylic acid) with high water absorbency using pineapple-leaf extracted cellulose fibers

This study synthesized cellulose-g-poly(acrylic acid) with high water absorbency using the cellulose extracted from pineapple leaves. The synthesis experiment used a novel combination of ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as the cross-linker and the initiator, respectively. Experimental results showed that the concentrations of AIBN and EGDMA had significant effects on the structure and the water absorbency of the cross-linked materials. The cellulose-g-poly(acrylic acid) synthesized with 0.5 wt% AIBN and 0.5 wt% EGDMA had an excellent swelling capacity of 1900 g/g in distilled water, significantly larger than previously reported ones. Compared with poly(acrylic acid), the cross-linked product demonstrated an absorbency improvement of 1.65 times in distilled water and 1.27 times in 8.6 ppm NaCl solution that was the highest salinity level in Ben Tre, Vietnam, in March 2020. Therefore, the obtained product showed high potential for agricultural applications, especially in coastal regions facing a growing thread of saltwater intrusion.

Isosorbide dinitrate template-based molecularly imprinted poly(methacrylic acid) nanoparticles: effect of initiator concentration on morphology and physicochemical properties

In this work, poly(methacrylic acid) (PMAA)-based molecularly imprinted polymer nanoparticles (MIP NPs) using isosorbide dinitrate (ISDN) as a template were prepared via a precipitation polymerization. The morphology and performance of the samples were investigated by varying different concentrations of azobisisobutyronitrile (AIBN) as an initiator. The MIP NP sample characterization as a function of the initiator concentration was evaluated utilizing Fourier transform infrared (FTIR) spectroscopy and field emission-scanning electron microscopy (FE-SEM) analyses. Regarding the washed MIP NP samples, the FTIR spectra results showed two main characteristic peaks located at 3339 and 1734 cm−1 wavenumbers corresponding to hydroxyl (–OH) and carbonyl (–C=O) groups, respectively. The intensity of these main peaks for the washed MIP NPs was higher than that of those for unwashed MIP NPs in which the active sites were appropriately formed between the polymer and template. These observations were occurred at the maximum amount of AIBN concentration (3 mmol). Moreover, the FE-SEM micrograph images exhibited an average diameter of approximately 40 nm for the MIP NP sample prepared with a low concentration of the initiator (0.5% of polymerizable double bonds). Furthermore, another two key factors for the MIP NPs such as binding capacity, and surface area using Barrett–Joyner–Halenda (BJH) method were studied to apply them for drug delivery systems potentially. On the other hand, the release of ISDN from MIP NP was considered through phosphate buffer saline (PBS, pH 7.4) at 37 °C for 5 days. The results showed higher ability of the sample compared with the non-imprinted polymer (NIP) ones to control the drug release, and kinetic trend of the drug absorption within the MIP NPs followed the pseudo-first model. Finally, the obtained outcomes showed that the low amounts of the initiator concentration have an indispensable role on the physicochemical properties of the synthesized MIP NPs.

SYNTHESIS AND CHARACTERIZATION OF LAURYL METHACRYLATE – GRAFT - POLYPROPYLENE FIBER

The graft polymerization of lauryl methacrylate (LMA) onto polypropylene fiber (PP) was investigated by using 2,2’-azobisisobutyronitrile (AIBN) as initiator. The grafting was influenced by AIBN concentration, monomer concentration, the reaction time and reaction temperature. On the basis of a detailed investigation of these factor, the optimal conditions for the grafting of LMA onto PP with the said initiator were as follows: [AIBN] = 0.015 mol/l, [LMA] = 1.25 mol/l, reaction time 240 min, reaction temperature 80 oC, in which the graft yield (%GY) of 15.7 % was obtained. Characterization of the polypropylene fiber-graft-lauryl methacrylate was done by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).

Modeling of Methyl Methacrylate Polymerization Using MATLAB

Abstract This paper presents a modeling of methyl methacrylate (MMA) polymerization with toluene in the presence of azo-bi’s-isobutyronitrile (AIBN) using MATLAB. This work aims to optimize the initial concentration of initiator and the reactor temperature to achieve a maximum monomer conversion in minimum batch time. The optimization of solution polymerization of MMA based on the three-stage polymerization model (TSPM) was performed using ode23t solver. The non-linear polymerization kinetics considered the gel, glass and cage effect to obtain a realistic prediction. The predicted reactor and jacket temperature showed a reasonable agreement with the experimental data, where the error is about 2.7 % and 2.3 %, respectively. The results showed that a maximum monomer conversion of 94 % was achieved at 0.126 kgmol m–3 of the initial concentration of AIBN and 346 K of the initial reactor temperature in 8,951 s (2.5 h).

Radiation-grafting of ethylene glycol dimethacrylate (EGDMA) and glycidyl methacrylate (GMA) onto silicone rubber

Silicone rubber (SR) was modified with a graft of ethylene glycol dimethacrylate (EGDMA) and glycidyl methacrylate (GMA) using either gamma-radiation or azobisisobutyronitrile (AIBN). The graft efficiency was evaluated as a function of monomer concentration, absorbed dose, reaction temperature, and concentration of AIBN. The hydrophilicity of the grafted films was measured by contact angle and their equilibrium swelling time in ethanol. Additional characterization by infrared (FTIR-ATR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is also reported.

Radical Polymerization of TFEMA and Relationship Between Surface Hydrophobicity and Molecular Weight of Poly-TFEMA

Conventional free radical polymerization of 2,2,2-trifluoroethyl methacrylate (TFEMA) with 2,2′-Azobisisobutyronitrile (AIBN) as initiator has been investigated. With isoamyl acetate as solvent, the effects of polymerization conditions, such as reaction temperature and concentrations of AIBN, on both the yield and number average molecular weight (Mn) of polymers were investigated in detail. For bulk polymerization of TFEMA, the molecular weight was as high as 1,471,000 with the monomer conversion up to 90% when the reaction temperature was 60°C and AIBN was 0.5 wt% to monomer. Interestingly, the experiment results showed that the water contact angles of the poly-TFEMA films increased from 98 ± 1° to 118 ± 1° when the Mn of poly-TFEMA increased from 95,000 to 1,471,000. Surface analysis techniques, including contact angle measurement, atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), were used to characterize the surface hydrophilicity, roughness, surface morphology and chemical composition of the polymer films. The results demonstrated that the degree of the roughness of the film surface increased with an increase of polymer molecular weight while the surfaces chemical compositions had almost no significant variation. The changing of the water contact angle with the Mn of the poly-TFEMA is likely due to the roughness of the film surface which depended on the Mn of the poly-TFEMA.

N‐Hydroxyphthalimide‐Mediated Oxidation of Styrene by Molecular Oxygen

In this work, the N‐hydroxyphthalimide (NHPI) is used for the oxidative polymerization of styrene at 25–100 psi oxygen pressure at 35–55 °C to obtain a faster rate of polymerization than in 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerizations. The rates for oxidative polymerization are determined from the oxygen consumption (Δp) against time plots and NHPI shows a reaction rate increased several fold compared with AIBN. The kinetics of the oxidative polymerization reactions are studied at various concentrations of oxygen, NHPI, AIBN, and monomer. The polymerization rate of styrene is almost the same when the NHPI analogue, N‐hydroxysuccinimide (NHSI), is employed. A mechanism of oxidative polymerization in the presence of NHPI is suggested on the basis of the kinetic data and characterization results of poly(styrene peroxide) (PSP). The NHPI is efficient in initiation of the oxidative radical polymerization of styrene. image

Direct Evidence of 2-Cyano-2-Propoxy Radical Activity During AIBN-Based Oxidative Stress Testing in Acetonitrile–Water Solvent Systems

Oxidative susceptibility testing was performed on a drug substance containing a methoxy-naphthalene moiety. 2,2'-azobisisobutyronitrile (AIBN) was employed to initiate peroxy radical oxidation to mimic autoxidation processes. In acetonitrile (ACN)-water solvents, three major degradation products are formed. However, addition of small amounts of methanol to the solvent system completely eliminated the observed degradation products. To understand this effect, the structures of the three degradants have been elucidated using nuclear magnetic resonance, liquid chromatography-tandem mass spectrometry, and accurate mass Fourier transform ion cyclotron resonance mass spectrometry. One degradant structure definitively proves the degradation resulted from alkoxy radicals (2-cyano-2 propoxy radical) arising from the disproportionation of the tertiary AIBN-derived peroxy radicals, rather than from the intended action of the AIBN peroxy radicals themselves. The reaction occurs over a wide range of AIBN and drug substance concentrations. This "protective effect" of several percent methanol by volume is rationalized by known methanol H atom donation rates to similar tert-butoxy and cumyloxy radicals (ca. 10 M(-1) s(-1) ) and the high methanol concentration relative to the dilute substrate being investigated. This work confirms recent proposals for addition of at least about 10% methanol to the standard ACN-water AIBN stress testing diluent to insure that only the desired peroxy radical activity is present during the oxidative stress test.

Synthesis and characterization of pH‐sensitive crosslinked (NIPA‐co‐AAC) nanohydrogels copolymer

AbstractA thermoresponsive polymeric nanohydrogels has been synthesized by inverse microemulsion polymerization of N‐isopropylacrylamide (NIPA) and acrylic acid (AAc) using Aerosol (AOT) as a surfactant, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The effect of concentration of AIBN, EGDMA, and NIPA/AAc weight ratio was investigated. The lower critical solution temperature (LCST) of poly (NIPA‐co‐AAC) can be manipulated to be 40°C and 45°C which was correlated to amount of AAc that was copolymerized with NIPA. FTIR, 1H NMR, TEM, and DSC characterized the nanohydrogels. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Precipitation polymerization in acetonitrile and 1-propanol mixture: synthesis of monodisperse poly(styrene-co -divinylbenzene) microspheres with clean and smooth surface

Precipitation polymerization of styrene (St)–divinylbenzene (DVB) has been carried out using acetonitrile/1-propanol mixture as the reaction media and 2,2′-azobisisobutyronitrile (AIBN) as initiator. Monodisperse micron-sized poly(St-co-DVB) microspheres with clean and smooth surface were synthesized in the absence of any stabilizing agent such as surfactants or steric stabilizers. The effects of various polymerization parameters such as 1-propanol fraction in the reaction media, initiator and total monomer concentration, DVB content, polymerization time and polymerization temperature on the morphology, particle size and size distribution were investigated. It was found that smoothly shaped stable particles were obtained when less than 70 vol% of 1-propanol was used in the media. The particle size increased with the AIBN concentration, whereas the change of uniformity was less obvious. Monodisperse microspheres were obtained when the total monomers loading ranged from 0.5 to 3 vol%. The particle diameter ranged from 2.73 to 1.87 µm with an increasing DVB content and the uniformity was enhanced. In addition, the yield of microspheres increased with the increasing total monomer, initiator, and DVB concentration and polymerization time. Copyright © 2010 John Wiley & Sons, Ltd.

Characterization and modification of commercial acrylic fibers grafted with acrylic acid

AbstractThe graft copolymerization of acrylic acid (AA) onto commercial acrylic fibers (PAN) has been studied using Azobis(isobutyro)nitrile (AIBN) as an initiator. AA grafting initiated by radicals formed from thermal decomposition of AIBN. In this study, the effects of monomer and initiator concentration, time and temperature reaction on the grafting yield have been investigated. The optimum conditions for this grafting reaction were obtained with an AA concentration of 1.67 M, an AIBN concentration of 0.0097 M, a reaction temperature of T=85 °C and with reaction time of 60 minutes.The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water absorption and also in this study has been investigated the mechanical property. The thermal analysis data showed that increasing in grafting yield, decreases the thermal stability of fiber. Grafting also affected slightly the fiber morphology. The experimental data of mechanical properties show clearly that by increasing of grafting yield, max extension will decrease. Grafting of poly AA improved water absorption.

Synthesis of functional polypropylene via solid-phase grafting soft vinyl monomer and its mechanism

Solid-phase grafting of a soft vinyl monomer, butyl methylacrylate (BMA), onto polypropylene (PP) matrixes with 2,2′-azobisisobutyronitrile (AIBN) as initiator was carried out to enhance the polarity of polymer. Soft vinyl monomer was a novel notion in grafting modification of PP. Effects of swell time, BMA concentration, AIBN concentration, grafting reaction time, and temperature on grafting percentage (Gp) and grafting efficiency (Ge) were examined. The optimal conditions of grafting reaction were obtained: swell time of 60 min, BMA concentration of 6 wt %, AIBN concentration of 0.05 wt %, reaction temperature of 85°C, and reaction time of 2 h. The grafting samples were investigated by such characterization techniques as Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscope (SEM) analysis. FTIR results indicated that BMA was actually grafted onto PP backbone. TGA results showed that the decomposition temperature increases with addition of BMA into PP backbone. SEM results indicated that the surfaces of PP-g-BMA had a markedly bumpy texture, whereas the pure PP surface was very smooth. Water contact angle results showed that the polarity and hydrophilicity of PP were improved effectively. Compared with the traditional monomer MAH, Gp, and Ge, melt flow rate and mechanical property results all indicated that the soft vinyl monomer had a many advantages in the modification of PP. In the end, the mechanism of solid grafting was discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of Reaction Parameters on Size Distribution of Emulsion-Polymerized Polystyrene Latex Beads Studied by Gravitational Flow-Flow Fractionation (GrFFF)

A gravitational field-flow fractionation (GrFFF) was employed to study the influence of various reaction parameters in emulsion polymerization on size distribution of polymeric latex beads. Micron-sized polystyrene (PS) latex beads were synthesized by conventional emulsion polymerization. The reaction parameters such as the stirring rate (rpm), reaction time, concentration of azobisisobutyronitrile (AIBN) and polyvinylpyrrolidone (PVP), were systematically varied. Then the PS beads were analyzed by GrFFF for size determination. It was found that the mean diameter and the size distribution of the PS latex beads change as some of the reaction parameters change. No clear trends were observed in the mean diameter and the coefficient of variation (CV) with the stirring rate in the range of 60 to 300 rpm, or with the reaction time in the range of 13 to 24 hrs. A clear trend of increase in the mean diameter with the AIBN concentration was observed, suggesting the particle size can be controlled by varying the AIBN concentration without affecting the size distribution much. It was also found that the mean diameter tends to decrease as the PVP concentration increases while the CV tends to increase. Results obtained from GrFFF were compared with those obtained from photon-correlation spectroscopy (PCS) and optical microscopy (OM).

Synthesis of monodispersed poly(acrylonitrile) microspheres by dispersion polymerization in compressed liquid dimethyl ether

In this study, monodispersed spherical particles of poly(acrylonitrile) were synthesized via dispersion polymerization in compressed liquid dimethyl ether using 2,2′-azobisisobutyronitrile (AIBN) as an initiator and five kinds of surfactants: PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA™), PDMS modified surfactants, SS-5050K™, KF-6017™, poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10- heptadecafluorodecyl acrylate), and poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate). Using Monasil PCA as a surfactant, uniform and spherical polymer particles were generated. The size of the microsphere particles was reduced via an increase in the concentration of Monasil PCA and a reduction in the monomer concentration. Increases in the concentration of AIBN resulted in a broad distribution of microspheres. Reaction temperature and pressure did not exert significant effects on the size and size distribution of the polymer particles.

Characterization and Studies on Grafting of Methyl Methacrylate onto PAN Fibers

The graft copolymerization of methyl methacrylate (MMA) onto commercial acrylic fibers (PAN) has been studied using Azobis(isobutyro)nitrile (AIBN) as an initiator. MMA grafting initiated by radicals formed from thermal decomposition of AIBN. In this study, the effects of monomer and initiator concentration, time and temperature reaction on the grafting yield have been investigated. The optimum conditions for this grafting reaction were obtained with an MMA concentration of 0.7 M, an AIBN concentration of 0.0073 M, a reaction temperature of T=85°C and with a 60 min reaction time. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), calorimetric analysis (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water absorption and the physical and mechanical properties has also been investigated in this study. The thermal analysis data showed that by increasing grafting yield, little changes have occurred in fibers samples up to 13.5% of grafting yield and the thermal transitions of grafted fibers have approximately the same behavior compared with the raw fibers sample. Grafting also slightly affected the fiber morphology. The experimental data of mechanical properties clearly show that by increasing grafting yield, max extension will decrease but this change up to 13.5% grafting yield is barely noticeable. Grafting of poly MMA improved water absorption.

Solvent‐free free‐radical frontal polymerization: A new approach to quickly synthesize poly(N‐vinylpyrrolidone)

AbstractThe first synthesis of poly(N‐vinylpyrrolidone) without solvent by free‐radical frontal polymerization at ambient pressure is reported. The appropriate amounts of two reactants N‐vinyl‐2‐pyrrolidone (NVP) and initiator 2,2′‐azobis‐isobutyronitrile (AIBN) without solvent were mixed together at ambient temperature. Frontal polymerization was initiated by heating the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self‐propagate throughout the reaction vessel. Once initiated, no further energy was required for polymerization to occur. To suppress the fingers of molten monomer, a small amount of nanosilica was added. The dependence of the front velocity and front temperature on the AIBN concentration was thoroughly investigated. The as‐prepared polymers were characterized by gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). Results show that without postpolymerization solvent removal, waste production can be reduced. Solvent‐free FP could be exploited as a means for preparation of PVP with the potential advantage of higher throughput than solvent‐based methods. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2177–2185, 2008

GMA-functionalized reactive stabilizer for polymerization of methyl methacrylate in supercritical CO2: effect of stabilizer, initiator and monomer concentrations

Glycidyl methacrylate linked poly(dimethylsiloxane) (GMA-PDMS) was synthesized and used as a stabilizer for the dispersion polymerization of methyl methacrylate (MMA) in supercritical CO2. This study examined the effect of the concentrations of the stabilizer, 2,2’-azobisisobutyronitrile (AIBN) initiator, and MMA on the yield, molecular weight, and morphology of the poly(methyl methacrylate) (PMMA) product. PMMA was obtained in 94.6% yield using only 0.87 wt% GMA-PDMS. When the AIBN concentration was increased from 0.25 to 1.06 wt%, the molecular weight and particle size of the PMMA decreased from 56,600 to 21,600 and from 4.1 to 2.7 μm, whereas the particle size distribution increased from 1.3 to 1.9. TheMn of the PMMA product ranged from 41,600 and 55,800 under typical polymerization conditions. The PMMA particle diameter ranged from 1.8 to 11.0 μm and the particle size distribution ranged from 1.4 to 1.8.

Otrzymywanie preform metoda miedzyfazowej polimeryzacji zelowej

A method of preparation of poly(methyl methacrylate) (PMMA) preforms, showing gradient distribution of refractive index difference (An), in interfacial gel polymerization of methyl methacrylate (MMA) (Table 2 and 3) was elaborated. The effects of: radical initiator type [2,2'-azobisisobutyronitrile (AIBN) or benzoyl peroxide (NB)], its amount (0.001 or 0.002 mol/dm 3 ), amount of chain transfer agent (dodecyl mercaptan - MD, 0.01-0.03 mol/dm 3 ) as well as amount of bromonaphthalene (BN, 5-24 wt. %, being unreactive additive showing higher refractive index than polymer matrix, on the character of the curves illustrating An courses in the preforms were investigated (Figs. 1-8). It has been found that the preforms showing An courses nearly ideal were obtained when BN concentration was 17 wt. % and AIBN was used as an initiator. Mutual ratio of AIBN and MD concentrations allowing eliminating the bubbles' forming in the preform has been determined. These preforms can be used as precursors for gradient-index polymer optical fibers.