Acrylic emulsifier-free emulsion polymerization containing hydrophilic hydroxyl monomer in the presence or absence of nano-SiO2

The acrylic emulsifier-free emulsion polymerization containing hydrophilic hydroxyl monomer (23 wt.%) in the presence or absence of nano-SiO₂ particles was studied. The effects of reaction temperature, level of nano-SiO₂, variation of core monomer composite on the coagulum, particle size and monomer conversion were investigated. Transmission electron microscopy (TEM) was used to observe the particle morphology in the presence of nano-SiO₂ particles. It showed that the systems produced larger size of particles than that with emulsifier, and the addition of nano-SiO₂ particles increased the particle size but decreased the coagulum. When polymerization temperature rose from 65 °C to 80 °C, the coagulum produced decreased greatly irrelative of the existence of nano-SiO₂, and the particle size decreased with nano-SiO₂ but increased without nano-SiO₂. The increase of level of acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) in core monomer composite all decreased particle sizes; furthermore, the level of AA had more efficiency than the level of HEMA irrespective of the existence of nano-SiO₂ particle.     

SYNTHESIS OF POLY(ACRYLIC ACID-CO-ITACONIC ACID) IN CARBON DIOXIDE–METHANOL MIXTURES

ABSTRACT

High fluidity solvents, such as supercritical fluids, have several advantages over traditional solvents as polymerization media, such as offering a more environmentally-friendly reaction media, providing increased reaction rates, and simplifying the separation and purification of polymers. In this study, a traditional glass-ionomer polymer, poly(acrylic acid-co-itaconic acid) (PAA/IA) was synthesized by using mixtures of CO₂ and methanol as the reaction solvent and was characterized by ¹H-NMR, FT-IR, GPC, and viscometry. The mechanical and working properties of the glass-ionomer cements, prepared by mixing aqueous solutions of the polymers with Fuji II glass powder, were evaluated for compressive strength (CS), diametral tensile strength (DTS) and flexural strength (FS), as well as setting time and working time. The results showed that the polymerization reaction in CO₂/methanol mixtures was faster and had higher conversion than the polymerization reaction in water. The glass-ionomer formulations made from the copolymer prepared under SC conditions showed higher CS, comparable FS and DTS compared with those made from the same polymer prepared in water. Both of the synthesized copolymers had significantly higher CS and FS than Fuji II. The working properties of PAA/IA made in CO₂/methanol met the requirement of ANSI/ADA No. 96.     

Monolayer oxide catalysts from alkoxide precursors, part IV. Vanadia, titania and stibia on SiO2, SnO2, and TiO2 in 2-propanol oxidation

Vanadia monolayer catalysts supported on SnO₂, ZrO₂, TiO₂, and SiO₂, similarly as titania and stibia monolayers deposited on SiO₂, have been synthesized by reacting the corresponding metal alkoxides with hydroxyls on the carrier surfaces. The metal ions loads in monolayer systems were determined. The catalysts activity was tested in 2-propanol transformations. The nature of carrier has a strong influence on the dehydrating to dehydrogenating activity ratio of vanadia monolayer.     

A novel zirconocene/ultradispersed diamond black powder supported catalytic system for ethylene polymerization

A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al₂O₃ was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp₂ZrCl₂/UDDBP, Cp₂ZrCl₂/Al₂O₃, Cp₂ZrCl₂/MAO/UDDBP and Cp₂ZrCl₂/Al₂O₃/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed.     

The Effect of Nano-SiO2 Colloid on Soap-free Emulsion Polymerization of Methyl Methacrylate and Hydroxyethyl Methacrylate

Soap-free emulsion polymerization of methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) was carried out in the presence of colloidal nano-SiO₂ particles. The effect of nano-SiO₂ level on the monomer conversion, polymerization rate (Rp), and emulsion stability was investigated. The viscosity, particle size distribution of the emulsions, surface tension, and ionic conductivity of these systems were determined. Upon the introduction of the nano-SiO₂ particles into this system, the Rp and monomer conversion increased and the average particle size of the P(MMA-HEMA) emulsion decreased in comparison to emulsions formed in the absence of nano-SiO₂. However, the particle size distribution became broader to some degree. Scanning electron microscope observations demonstrated that the shape of these latex particles were uniformly spherical. The surface tension and ionic conductivity of the system increased significantly after polymerization, but the presence of nano-SiO₂ resulted in an increase in surface tension and a decrease in ionic conductivity in comparison to the particle–free system.     

Nanocomposite particles with core-shell morphology II. An investigation into the affecting parameters on preparation of Fe3O4-poly (butyl acrylate-styrene) particles via miniemulsion polymerization

The encapsulation of inorganic particles with polymers is desirable for many applications in order to improve the stability of the encapsulated products and disperse ability in different media. Colloidal particles with magnetic properties have become increasingly important both technologically and for fundamental studies. This is due to their tunable anisotropic. In the absence of an applied magnetic field, the particles have isotropic sphere dispersion, whereas in an external magnetic field the particles form anisotropic structures. Here, latexes containing nanocomposite particles of styrene-butyl acrylate/Fe₃O₄ with core-shell structure were prepared through miniemulsion polymerization technique. Magnetic composite nanospheres with high magnetic content were synthesized through miniemulsion polymerization using a new process based on a three-steps preparation route including two miniemulsion processes: (1) preparing a dispersion of oleic acid coated magnetite particles in water; (2) mixing of modified magnetite particles with styrene/butyl acrylate in the presence of sodium dodecyl sulfate (SDS), sorbitane mono oleate (Span 80), hexadecane (HD) and (3) miniemulsification of the modified Fe₃O₄ into the monomer droplets to reach to complete encapsulation. Subsequent polymerization generated magnetic nanocomposite spheres. Hence, the copolymerization reaction was performed on the surface of such particles in order to obtain core-shell morphology for these nanoparticles, which were characterized by several techniques such as TEM, SEM, DLS, TGA, VSM and FT-IR. The magnetic copolymer particles with diameter of 120-170 nm were obtained. The effect of several parameters such as magnetite, surfactants and hydrophobe amounts on the stability, particle size and magnetization were investigated and also optimized.     

Polymer-Titanium hybrids obtained by radical polymerization and Sol-Gel process

The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl acrylate) (PEtA) with TiO₂ was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl acetate (VAc). The PVAc-TiO₂ hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly affected by TiO₂ presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of TiO₂ inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network.     

Photosensitized Solid-state Polymerization of Diacetylenes in Nanoporous TiO2 Structures

In situ topochemical polymerization of two diacetylene monomers within nanoporous TiO₂ thin films was carried out under visible light irradiation. One of the monomers used contains a carboxylic acid group, which could help to link the monomer onto the TiO₂ surface covalently. UV-Vis absorption and Raman studies showed that both monomers were successfully photopolymerized. These results suggest that the covalent linkage of the diacetylene to the nanoparticle through the carboxylic acid group is not needed. Since photopolymerization of diacetylene is typically induced by excitation of the monomer at λ< 300 nm, the observed red shift of the photopolymerization wavelength is attributed to the photosensitization effect of TiO₂. The morphological study of the polydiacetylene/TiO₂ nanocomposite revealed that the diacetylene monomers were polymerized in the vicinity of the TiO₂ nanoparticles. This is attributed to the fact that the electron-transfer process occurs at the interface of nanocrystalline TiO₂ (nc-TiO₂) and the diacetylene monomer and the polymerization is expected to be initiated near the nc-TiO₂ surface. Photopolymerization of the carboxylated diacetylene monomer with other oxides nanoparticles, such as ZnO and SiO₂ was also investigated.     

Studies on Acrylic Emulsion Polymerization Containing Hydrophilic Hydroxyl Monomer in the Presence of Nano‐SiO2 Particles

Emulsion polymerization with nano‐scale SiO₂ particles as seeds composed of methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA), and acrylic acid (AA) was studied from varying reaction temperatures, level of SiO₂ particle, HEMA, and emulsifier. The morphology of the emulsion particle was examined with a transmission electron microscope (TEM). The results showed that the addition of nano‐SiO₂ particles decreased the coagulum greatly when its level was lower than 7%. The coagulum also decreased with the increasing of temperature from 65°C to 75°C. The level of HEMA and emulsifier had little influence on the coagulum in the presence of nano‐SiO₂. The particle size of the emulsion increased with the increase of level of nano‐SiO₂ and HEMA. Part of the emulsion particles connected together due to the existence of HEMA, and yet some of the nano‐SiO₂ particles were not covered with polymer.     

Dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) using siloxane-based surfactant in supercritical carbon dioxide and in compressed liquid dimethyl ether

The free radical dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) has been carried out in supercritical carbon dioxide (scCO₂) and compressed liquid DME using several surfactants. The polymerization are performed in the presence of fluorine-based poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate) [poly(HDFDA)], poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate) [poly(HDFDMA)], or poly(HDFDMA-co-MMA) and siloxane-based PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA™) or PDMS modified surfactants, SS-5050K™ and KF6017™ as polymerization surfactants. When scCO₂ was used as a polymerization medium, the PHEMA were heavily agglomerated. However, the spherical and relatively uniform poly(2-hydroxyethyl methacrylate) (PHEMA) particles could be produced even at 20 bar, with a narrow particle size distribution in compressed liquid DME. It was observed that fluorine-based surfactants were not a good surfactant as siloxane-based surfactants for the dispersion polymerization of HEMA. The average particle size of PHEMA was shown to be dependent on the type of the surfactant, the amount of the surfactant and initiator added to the system. The effect of two continuous phases, which are scCO₂ and compressed liquid DME, as a polymerization medium, the surfactant types and the concentration, initiator concentration, and monomer concentration on the morphology and size of the polymer particles was also investigated.     

Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

Reactivity and Characterization of the Radical Copolymerization of Itaconic Acid with Some Conventional Monomers

Abstract

Radical copolymerizations of itaconic acid (IA) with acrylamide (Am), N-vinyl pyrrolidone (NVP), ethyl methacrylate (EMA), and methyl methacrylate (MMA) were carried out in dioxane in the presence of azobisisobutyronitrile as the initiator at 65°C. The monomer reactivity ratios (r ₁, r ₂), Q, and e for IA with the four monomers were determined. The reactivity ratios show a tendency toward alternation, while the Q and e of IA indicate that it is an electron-accepting monomer. The polymers obtained were characterized by FT-IR, x-ray diffraction, intrinsic viscosity, and thermal stability measurements.     

Synthesis and Characterization of Hyperbranched Polyesters Based on Isophthalic Acid and Trimethylolpropane

Hydroxyl-terminated hyperbranched polyesters (HBPEs) with aromatic/aliphatic structure were synthesized at three different monomer mole ratios (A₂/B₃=1, 0.9, and 0.6, respectively) by melt polycondensation of isophthalic acid and trimethylolpropane via A₂+ B₃ approach. Fourier transform infrared (FTIR) spectroscopy indicated that the expected HBPEs, which showed excellent solubility in a variety of polar solvents such as N, N-dimethyl formamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and terahydrofuran (THF), were produced without gelation during the polymerization. The weight-average molecular weight of HBPEs ranged from 7014 to 8306 and their inherent viscosities were varied from 0.17 to 0.34 dL/g. The degree of branching of the HBPEs was estimated to be 0.39–0.49 by¹H-NMR and ¹³C-NMR measurement. Their glass transition temperature measured by differential scanning calorimetry (DSC) was between 64 and 86°C. The thermogravimetric analysis (TGA) measurement revealed that HBPEs had ca 8.5% weight-loss at 300°C in N₂.     

Effect of Cu(II)/H2 Salen complex on the non-conventional initiated emulsion polymerization of acrylonitrile

Radical polymerization of acrylonitrile was carried out in an emulsifier-free condition initiated by KHSO₅ catalyzed with Cu(II)/bis-salicylidene ethylene diamine (H₂ Salen) complex. The Cu(II) salt alone, Cu(II)/salicylaldehyde and Cu(II)/ethylene diamine have a retarding effect on the polymerization reaction, while the chelate of Cu(II) with the tetradentate Schiff base ligand, H₂ Salen has a catalytic effect. Prior to this, the catalytic effect of various bivalent transition metal salts and their couple with the Schiff base, H₂ Salen on the polymerization reaction has been examined to be not significant. The in situ developed complex produces the stable emulsion leading to high conversion. In the polymerization, the variables studied were the concentration of monomer, initiator, Cu(II), H₂ Salen and temperature. The overall activation energy was computed to be 13.1 kcal/mol. From the kinetic and spectral analyses, the mechanism of the initiator decomposition and initiation of polymerization by Cu(II)/H₂ Salen complex were suggested. The rate of polymerization (R_p) was found to be dependent on the monomer, initiator, Cu(II) ion, H₂ Salen concentrations to the 1.4, 0.3, 1.6, 1.5 power respectively. The polymers are characterized by IR and molecular weight by viscosity and GPC methods.     

Preparation of ZrO2-TiO2-CeO2 and Its Application in the Selective Catalytic Reduction of NO with NH3

TiO₂,ZrO₂-TiO₂,andZrO₂-TiO₂-CeO₂ were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH₃-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results showed that ZrO₂-TiO₂-CeO₂ exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V₂O₅ and 9% (w)WO₃ for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O₂, and the results of catalytic activity showed that the catalyst used ZrO₂-TiO₂-CeO₂ as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h⁻¹, and it had the best catalytic activity and showed great potential for practical application.     

二硫桥键钴卟啉二聚体的合成与电催化氧还原性能

成功合成了二硫桥键相连的钴卟啉二聚体2Co。通过循环伏安电化学方法测试,在无水二氯甲烷溶剂中,钴卟啉二聚体展示了3个氧化和2个还原峰,表明此钴卟啉二聚体可以稳定多重负/正电荷。详细研究了在酸性条件下的钴卟啉二聚体的电催化氧还原性能。钴卟啉二聚体的电催化氧还原显示了高稳定性和高活性,测得转移电子数为3.5~3.6之间。钴卟啉二聚体的电催化氧还原性能说明通过二硫键对钴卟啉单体二聚化可以提高钴卟啉的电催化氧还原性能。     

Synthesis of nano-sized crystalline oxide ion conducting fluorite-type Y2O3-doped CeO2 using perovskite-like BaCe0.9Y0.1O2.95 (BCY) and study of CO2 capture properties of BCY

Formation of nano-sized Y₂O₃-doped CeO₂ (YCO) was observed in the chemical reaction between proton conducting Y₂O₃-doped BaCeO₃ (BCY) and CO₂ in the temperature range 700-1000 °C, which is generally prepared by wet-chemical methods that include sol-gel, hydrothermal, polymerization, combustion, and precipitation reactions. BCY can capture CO₂ of 0.13 g per ceramic gram at 700 °C, which is comparable to that of the well-known Li₂ZrO₃ (0.15 g per ceramic gram at 600 °C). Powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDX), laser particle size analysis (LPSA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ac impedance spectroscopy were employed to characterize the reaction product obtained from reaction between BCY and CO₂ and subsequent acid washing. PXRD study reveals presence of fluorite-like CeO₂ (a=5.410 (1) Å) structure and BaCO₃ in reaction products. TEM investigation of the acid washed product showed the formation of nano-sized material with particle sizes of about 50 nm. The electrical conductivity of acid washed product (YCO) in air was found to be about an order higher than the undoped CeO₂ reported in the literature.     

Electroreductive polymerization of trans-[RuCl 2(vpy) 4] on Nd-Fe-B magnets: electrochemical impedance spectroscopy interpretation, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy analysis

The electropolymerization of trans-[RuCl₂(vpy)₄] (vpy=4-vinylpyridine) monomer on Nd-Fe-B magnets was studied by electrochemical impedance spectroscopy (EIS). Impedance diagrams obtained during the polymerization process were used to monitor film formation. The EIS results gave insight into the electrochemical phenomena occurring at the magnet surface as the polymerization process progressed. The film structure and morphology were also studied by X-ray photoelectron spectroscopy, scanning electron microscopy and Raman spectroscopy. The Raman spectroscopy results showed that the polymerization takes place at the vinyl groups of the monomer and also that the redox polymer structure is very similar to that of the monomer. The ratio of the intensity of the XPS peaks for fluorine (from the electrolyte PF₆ ^–) and ruthenium present in the film showed that the polymer on Nd-Fe-B contained an equal proportion of Ru²⁺ and Ru³⁺, indicating that part of the film is positively charged, i.e. {[RuCl₂(vpy)₄]⁺} _n .     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.