EMULSION COPOLYMERIZATION OF VINYL ACETATE IN PRESENCE OF ACID COMONOMERS

The interaction of acid comonomers, crotonic acid, maleic monoesters, maleic acid with the surfactant, the sodium salt of sulfosuccinic acid semiester with nonyl phenol etoxylated with 25 moles ethylene oxide (NPEO₂₅SS) depends on the hydrophilicity of comonomers. The rate of initiator splitting reaction (potassium persulfate - KPS) in presence of NPEO₂₅SS and of comonomers decreases with the increasing of acid comonomer concentration. This rule is valid in copolymerization of acid comonomers with vinyl acetate (VAc) below a small comonomer concentration, then the rate increases. The presence of some more hydrophobic comonomers maleic diesters, lowers the decomposition rate of KPS. These results are the effect of the stronger interaction of NPEO₂₅SS with more hydrophobic polymer particles. In their presence the concentration of free NPEO₂₅SS is lower and it can participate in the KPS - surfactant reaction and rise its rate to a lesser extent. Owing to some secondary acid comonomer - KPS reactions the productivity of initiator splitting decreases with acid comonomer concentration The glass transition temperatures of the thin films obtained in presence of acid comonomers, may increase or decrease, depending on the volume of the substituents of these comonomers.     

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.     

Selective synthesis of (E)-triethyl(2-arylethenyl)silane derivatives by reaction of aryl bromides with triethyl vinylsilane catalysed by a palladium-tetraphosphine complex

Cis, cis, cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane / 0.5 [PdCl(C₃H₅)]₂ system catalyses the Heck reaction of vinylsilane derivatives with a range of aryl bromides with high ratio substrate/catalyst in good yields. The formation of mixtures of styrene, (E)-triethyl(2-arylethenyl)silane and triethyl(1-arylethenyl)silane derivatives was observed in some cases. Very high selectivities (up to 100%) in favour of the formation of (E)-triethyl(2-arylethenyl)silane derivatives were obtained in the presence of sodium acetate as base. With other bases such as potassium carbonate, the formation of large amounts of styrene derivatives was observed. The reaction tolerates several functions such as fluoro, trifluoromethyl, methoxy, dimethylamino, acetyl, formyl, benzoyl, carboxylate, nitro or nitrile. Moreover, turnover numbers up to 10,000 can be obtained for this reaction.     

Poly(vinyl acetate‐co‐dibutyl maleate) latex films in the presence of grafted and post‐added poly(vinyl alcohol)

We describe the synthesis and characterization of a series of poly(vinyl acetate‐co‐dibutyl maleate) [P(VAc‐DBM)] latex particles (monomer molar ratio 10.6:1). One set of samples [high‐M and M_250k SDS‐P(VAc‐DBM), gel content 50% and 0%] was prepared in the presence of an anionic surfactant sodium dodecyl sulfate. The other two sets of samples [high‐M and M_250k PVOH–P(VAc‐DBM)] were prepared in the presence of poly(vinyl alcohol) (PVOH). These polymers differ in gel content (50 and 0%) and the extent of PVOH grafting (30 and 15%). Polymer diffusion across cell boundaries in the latex films was monitored by fluorescence resonant energy transfer (ET) experiments. First, we examined M_250k samples in the presence of grafted and post‐added PVOH. The presence of post‐added PVOH (5%) causes a small but detectable retardation on the rate of polymer diffusion, whereas the presence of grafted PVOH (degree of grafting: 15%) significantly promotes the polymer diffusion rate. For the high‐M P(VAc‐DBM), the presence of post‐added PVOH also retards the polymer diffusion. Strikingly, the presence of grafted PVOH (degree of grafting: 30%) in the high‐M PVOH‐P(VAc‐DBM) promotes the polymer diffusion to such an extent that the diffusion was complete in the freshly prepared films. Our data also suggest that under our experimental conditions, the rate of P(VAc‐DBM) diffusion increases with an increase of the degree of PVOH grafting. To confirm these results, we carried out fluorescence microscopy experiments to monitor the fate of PVOH in these latex films and found that in newly formed PVOH–P(VAc‐DBM) films, the PVOH was either uniformly distributed in the P(VAc‐DBM) matrix or the domains were too small to be resolved (i.e., < 0.5 μm). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5005–5020, 2004     

A cyclic selenium‐based reversible addition‐fragmentation chain transfer agent mediated polymerization of vinyl acetate

A cyclic selenium‐based reversible addition‐fragmentation chain transfer (RAFT) agent, 5,5‐dimethyl‐3‐phenyl‐2‐selenoxo‐1,3‐selenazolidin‐4‐one (RAFT‐Se), was synthesized and utilized in the RAFT polymerizations of vinyl acetate (VAc). Its analog, 5,5‐dimethyl‐3‐phenyl‐2‐thioxothiazolidin‐4‐one (RAFT‐S), was also used in RAFT polymerizations for comparison under identical conditions. The RAFT polymerizations of VAc with RAFT‐Se were moderately controlled evidenced by the increase of molecular weights with conversion, despite the slightly high M_w/M_n (less than 1.90), whereas the molecular weights were poorly controlled in the presence of RAFT‐S (2.00 < M_w/M_n < 2.30). Thanks to its unusual cyclic structure of RAFT‐Se, one or more RAFT‐Se species was incorporated into the resultant poly(VAc) as revealed by the results of cleavage of polymer and atomic absorption spectroscopy. Considering the biorelated functions of both poly(VAc) and Se element, this work undoubtedly provided a successful methodology of how to incorporate high content of Se into a molecular weight controlled poly(VAc). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

The effect of different polymer length on water droplets of reverse AOT microemulsion

We study the effect of polyethylene glycol (PEG) on the dynamic and structure of water droplets at the reverse sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) microemulsion. The mixture of water and oil with anionic surfactant AOT can form microemulsion. The dynamic of microemulsion in the presence of PEG is investigated by photon correlation spectroscopy technique. We mainly focus on the variation of the translational diffusion behaviour as a function of the polymer concentration and polymer length scale. By increasing the content of the lowest PEG length scale (M_n = 285), the dynamic of microemulsion slows down. In addition, one relaxation process is distinguished for all polymer concentration. However, for the two higher polymer length scale (M_n = 2200 and 6000), two relaxations are observed and the dynamic of microemulsion speeds up. We used the small angle X-ray scattering technique to monitor the size and the polydispersity of the mixture system (AOT microemulsion/PEG).     

Toxicity identification fractionation of environmental estrogens in waste water and sludge using gas and liquid chromatography coupled to mass spectrometry and recombinant yeast assay

We developed a toxicity identification fractionation (TIF) procedure to determine estrogenic compounds in wastewaters and sludge. The procedure consisted in fractionation of samples through a C₁₈ solid-phase extraction cartridge, in which Fraction I contained nonylphenol (NP) and its mono (NPEO₁) and diethoxylate (NPEO₂) and the markers of faecal exposure, Fraction II contained bisphenol A (BPA) and synthetic and natural hormones, and Fraction III contained the hormone conjugates. These three fractions were analyzed in parallel using gas or liquid chromatography coupled to mass spectrometry and recombinant yeast assay (RYA). Water samples collected daily throughout a whole week contained from 0.45 to 7.22 μg L⁻¹ of NP > NPEO₁ > NPEO₂ and were responsible for the estrogenicity of these samples. Fractions II and III were not estrogenic and that was due to the low ng L⁻¹ level of hormones and hormone conjugates found, respectively. The biological treatment sewage treatment plant (STP) was capable to eliminate from 52 to 100% of the compounds, with bisphenol A being the least removed. Only alkylphenols were accumulated in sludge with concentrations from 8.69 to 26.3 mg kg⁻¹ dw of NPEO₁ > NPEO₂ > NP. The integrated procedure herein proposed can be used as a screening method to evaluate estrogenic compounds in STPs and to survey faecal elimination.     

Identification of photocatalytic degradation products of non-ionic polyethoxylated surfactants in wastewaters by solid-phase extraction followed by liquid chromatography-mass spectrometric detection

The photodegradation of non-ionic surfactants (nonylphenol- and alcohol-polyethoxylates, NPEO_x and C_nEO_x) was investigated in different waters with and without a photoinducter (Fe(III)). Deionized water and industrial effluent spiked at 0.5 mg/L with C₁₀EO₆ and NPEO₉ were irradiated using a xenon arc lamp. Aliquots of the test solutions were taken at different time intervals and were preconcentrated using solid phase extraction (SPE) with C₁₈ cartridges. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) was used to identify the chemical species generated from phototransformation of non-ionic surfactants. 2 ) and nonylphenol ethoxy acetic acid (NPE₂C). Much smaller amounts of degradation products of NPEO₉ having only the alkyl chain carboxylated were also formed in the photocatalysis experiment. The identified C₁₀EO₆ photoproducts included fatty alcohols and acids. Polyethylene glycols (PEGs) were also formed as the consequence of the central scission of C₁₀EO₆ and the deethoxylation of NPEO₉. The photodegradation in wastewater samples was more efficient than in deionized water being the half-life (t_1/2) of C₁₀EO₆, 48 h and 29 h in deionized water and wastewater, respectively, and for NPEO₉, 17 h and 14 h in deionized water and wastewater, respectively. When induced photodegradation was undertaken, the t_1/2 for NPEO₉ was 21 min and 29 min in deionized water and wastewater, respectively. Disappearance of parent compounds was observed after 120 h from the beginning of the photodegradation experiment, or after 210 min of irradiation for the photocatalysis. Received: 27 September 2000 / Revised: 11 January 2001 / Accepted: 14 January 2001     

Synthesis of CdS/SiO2/polymer tri-layer fluorescent nanospheres with functional polymer shells

Tri-layer CdS/SiO₂/polymer hybrid nanospheres were synthesized by distillation precipitation polymerization of either ethyleneglycol dimethacrylate（EGDMA） or EGDMA together with comonomers having different functional groups, such as methacrylic acid,4-vinylpyridine and 2-hydroxyethylmethacrylate,in the presence of 3-（methacryloxy）propyl trimefhoxysilane（MPS）-modified CdS/SiO₂ nanoparticles as seeds in acetonitrile with 2,2’-azobisisobutyronitrile（AIBN） as initiator.In this approach,MPS-modified inorganic seeds were prepared by the modification of CdS/SiO₂ nanoparticles via the self-condensation reaction between the hydroxyl groups of sinaols,in which the CdS/SiO-2 nanoparticles were afforded by a reverse microemulsion technique for the synthesis of CdS core nanoparticles with the subsequent coating of silica layer. The polymer shell-layers encapsulated over the MPS-modified CdS/SiO₂ inorganic seeds via the efficient capture of the monomers and oligomers from the solution with the aid of the vinyl groups incorporated by the MPS modification,in which the polymer shell-thickness and functional groups including carboxyl,pyridyl and hydroxyl,were facilely controlled by the feed of EGDMA as well as the types of comonomers used for the polymerization.These nanospheres were characterized by transmission electron microscopy（TEM）,Fourier-transform infrared spectroscopy（FT-IR）,thermogravimetric analysis （TGA）,fluorescence spectroscopy and zeta potential.     

P(VAc-MMA)为基体的聚合物电解质研究

以醋酸乙烯酯(VAc)和甲基丙烯酸甲酯(MMA)为单体, 采用半连续种子乳液聚合法制备了无规共聚物聚(醋酸乙烯酯-甲基丙烯酸甲酯)[P(VAc-MMA)], 并以此聚合物为基体制备了聚合物电解质. 用红外光谱(FTIR)、核磁共振氢谱(¹H NMR)、扫描电镜(SEM)、差热/热重分析(DSC/TG)、X射线衍射(XRD)、机械性能测试和电化学交流阻抗等方法对聚合物和聚合物电解质的性质进行了研究. 测试结果表明: VAc和MMA聚合生成P(VAc-MMA); 聚合物膜含有大量微孔结构, 利于离子传输; 聚合物电解质膜具有优良的热稳定性和机械强度; 25 ℃下, 最高的离子电导率达到了1.27× 10^－3 S•cm^－1; 离子电导率随着温度的升高而迅速增加, 电导率-温度曲线符合Arrhenius方程.     

Photoionization of Oxidized Coenzyme Q in Microemulsion: Laser Flash Photolysis Study in Biomembrane‐like System

Photoexcitation to generate triplet state has been proved to be the main photoreaction in homogeneous system for many benzoquinone derivatives, including oxidized coenzyme Q (CoQ) and its analogs. In the present study, microemulsion of CoQ, a heterogeneous system, is employed to mimic the distribution of CoQ in biomembrane. The photochemistry of CoQ₁₀ in microemulsion and cyclohexane is investigated and compared using laser flash photolysis and results show that CoQ₁₀ undergoes photoionization via a monophotonic process to generate radical cation of CoQ₁₀ in microemulsion and photoexcitation to generate excited triplet state in cyclohexane. Meanwhile, photoreactions of duroquinone (DQ) and CoQ₀ in microemulsion are also investigated to analyze the influence of molecular structure on the photochemistry of benzoquinone derivatives in microemulsion. Results suggest that photoexcitation, which is followed by excited state‐involved hydrogen‐abstraction reaction, is the main photoreaction for DQ and CoQ₀ in microemulsion. However, photoexcited CoQ₀ also leads to the formation of hydrated electrons. The isoprenoid side chain‐involved high resonance stabilization is proposed to explain the difference in photoreactions of CoQ₀ and CoQ₁₀ in microemulsion. Considering that microemulsion is close to biomembrane system, its photoionization in microemulsion may be helpful to understand the real photochemistry of biological quinones in biomembrane system.     

Determination of arsenic species in solid matrices utilizing supercritical fluid extraction coupled with gas chromatography after derivatization with thioglycolic acid n‐butyl ester

A method using derivatization and supercritical fluid extraction coupled with gas chromatography was developed for the analysis of dimethylarsinate, monomethylarsonate and inorganic arsenic simultaneously in solid matrices. Thioglycolic acid n‐butyl ester was used as a novel derivatizing reagent. A systematic discussion was made to investigate the effects of pressure, temperature, flow rate of the supercritical CO₂, extraction time, concentration of the modifier, and microemulsion on extraction efficiency. The application for real environmental samples was also studied. Results showed that thioglycolic acid n‐butyl ester was an effective derivatizing reagent that could be applied for arsenic speciation. Using methanol as modifier of the supercritical CO₂ can raise the extraction efficiency, which can be further enhanced by adding a microemulsion that contains Triton X‐405. The optimum extraction conditions were: 25 MPa, 90°C, static extraction for 10 min, dynamic extraction for 25 min with a flow rate of 2.0 mL/min of supercritical CO₂ modified by 5% v/v methanol and microemulsion. The detection limits of dimethylarsinate, monomethylarsonate, and inorganic arsenic in solid matrices were 0.12, 0.26, and 1.1 mg/kg, respectively. The optimized method was sensitive, convenient, and reliable for the extraction and analysis of different arsenic species in solid samples.     

Syntheses of Vinyl Sulfoxide/Vinyl Acetate-Type Copolymers

The homopolymerization of a series of alkyl vinyl sulfoxides (CH₂[dbnd]CHSOR; R = CH₃ (MVSO), C₂H₅ (EVSO), t-C₄H₉ (BVSO)) and their copolymerization with vinyl acetate (VAc) with 2,2′-azobisisobutyronitrile (AIBN) as initiator at 60°C was attempted. MVSO was found to homopolymerize radically, but EVSO and BVSO were not. Poly-MVSO is soluble in chloroform, methanol, DMSO, and water, but insoluble in acetone and benzene. MVSO and EVSO were found to copolymerize with VAc, but BVSO was not. The copolymerization parameters obtained for both systems were as follows; r₁(MVSO) = 2.23, r₂ (VAc) = 0.09, and r₁(EVSO) = 3.40, r₂ (VAc) = 0.11, respectively. MVSO/vinyl alcohol (VA) copolymers were obtained through the saponification of MVSO/VAc copolymers by sodium hydroxide in methanol. The solubility of MVSO/VAc and of MVSO/VA copolymers toward various solvents was examined, and it was observed that the sulfoxide comonomer has a tendency to give amphiphilicit to poly(vinyl acetate) and poly(vinyl alcohol). The 24 mol% MVSO containing VAc copolymer is soluble in both benzene and water.     

Kinetic study of the crosslinking reaction of 1,2‐polybutadiene with dicumyl peroxide in the absence and presence of vinyl acetate

The crosslinking reaction of 1,2-polybutadiene (1,2-PB) with dicumyl peroxide (DCPO) in dioxane was kinetically studied by means of Fourier transform near-infrared spectroscopy (FTNIR). The crosslinking reaction was followed in situ by the monitoring of the disappearance of the pendant vinyl group of 1,2-PB with FTNIR. The initial disappearance rate (R₀) of the vinyl group was expressed by R₀ = k[DCPO]^0.8[vinyl group]^−0.2 (120 °C). The overall activation energy of the reaction was estimated to be 38.3 kcal/mol. The unusual rate equation was explained in terms of the polymerization of the pendant vinyl group as an allyl monomer involving degradative chain transfer to the monomer. The reaction mixture involved electron spin resonance (ESR)-observable polymer radicals, of which the concentration rapidly increased with time owing to a progress of crosslinking after an induction period of 200 min. The crosslinking reaction of 1,2-PB with DCPO was also examined in the presence of vinyl acetate (VAc), which was regarded as a copolymerization of the vinyl group with VAc. The vinyl group of 1,2-PB was found to show a reactivity much higher than 1-octene and 3-methyl-1-hexene as model compounds in the copolymerization with VAc. This unexpectedly high reactivity of the vinyl group suggested that an intramolecular polymerization process proceeds between the pendant vinyl groups located on the same polymer chain, possibly leading to the formation of block-like polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4437–4447, 2004     

Synthesis and properties of all solid polymer electrolytes based on poly(vinyl acetate‐co‐acetyl ethylene oxide acrylate)

Poly(acetyl ethylene oxide acrylate‐co‐vinyl acetate) (P(AEOA‐VAc)) was synthesized and used as a host for lithium perchlorate to prepare an all solid polymer electrolyte. Introduction of carbonyl groups into the copolymer increased ionic conductivity. All solid polymer electrolytes based on P(AEOA‐VAc) at 14.3 wt% VAc with 12wt% LiClO₄ showed conductivity as high as 1.2 × 10^?4 S cm^?1 at room temperature. The temperature dependence of the ionic conductivity followed the VTF behavior, indicating that the ion transport was related to segmental movement of the polymer. FTIR was used to investigate the effect of the carbonyl group on ionic conductivity. The interaction between the lithium salt and carbonyl groups accelerated the dissociation of the lithium salt and thus resulted in a maximum ionic conductivity at a salt concentration higher than pure PAEO‐salts system. Copyright © 2010 John Wiley & Sons, Ltd.     

Reactivity of metal-containing monomers 66. Hydrogenation of nitrotoluene derivatives in the presence of polymer-immobilized Pd nanoparticles

A new approach to the synthesis of immobilized catalysts of the mixed type was developed: frontal polymerization of metal-containing monomers in the presence of a highly dispersed inorganic support. The synthesis of the acrylamide complex of Pd^II nitrate on the SiO₂ surface followed by polymerization and reduction results in the formation of a polymer-inorganic composite with inclusions of Pd nanoparticles stabilized by the polymer matrix on the support surface. The study of the catalytic properties in the hydrogenation of nitrotoluene derivatives showed that the polymer-immobilized Pd nanoparticles on the inorganic support are efficient catalysts for the reduction of the nitrocompounds.     

Aspects of Living Radical Polymerization Mediated by Cobalt Porphyrin Complexes

Living radical polymerization (LRP) of methyl acrylate (MA), acrylic acid (AA), and vinyl acetate (VAc) mediated by cobalt(II) porphyrin complexes ((TMP)Co^II·, (TMPS)Co^II·) are reported. The polymeric products with relatively low polydispersity and controlled number average molecular weight (M_n) based on one polymer chain per cobalt complex demonstrate the living characters of the polymerization process. The formation of block copolymers of poly(methyl acrylate)‐b‐poly(vinyl acetate) (PMA‐b‐PVAc) and poly(methyl acrylate)‐b‐poly(vinyl pyrrolidone) (PMA‐b‐PVP) demonstrate another important feature of LRP and extend the application of cobalt porphyrin mediated radical polymerization to a wider array of functionalized monomers. Kinetic studies using ¹H NMR to follow the formation of orGano‐cobalt complexes reveal that two mechanisms, reversible termination (RT) and degenerative transfer (DT), occur during the polymerization process. MA and VAc polymerization mediated by cobalt porphyrin complexes are used to illustrate the properties of these two LRP pathways and evaluate the kinetic and thermodynamic properties for several of the central reactions.     

Oxidation of Alcohols by Hydroperoxides in the Presence of Polymer-Supported Catalysts: Tetrabromooxomolybdate Supported on a Cationic Polymer

The immobilization of Br₄MoO^? in both poly-p-vinyipyridine with a flexible backbone and silica as a rigid polymer support was carried out. The oxidation of alcohols by t-butyl hydroperoxide (t-BuOOH) was then studied in the presence of the polymer-supported complexes obtained. The differences of the reactivity between catalysts supported by organic and inorganic polymers are discussed. The best carrier for Br₄MoO^? as an oxidation catalyst is a silica modified with silane coupling reagent (dimethyloctadecyl-[3-(trimethoxysilyl)propyl] ammonium chloride).     

Production of organometallic polymers by the interfacial technique. V. Partial mechanistic study of the production of poly[alkyl(aryl)oxysilances]

A modified interfacial polymerization system capable of producing poly[alkyl(aryl)oxysilanes] consisting of a dichlorosilane in an organic solvent as octane and a diol in 2,5-hexanedione is presented. It is believed that polymerization occurs near the interface in the dione phase. The products are low to intermediate in molecular weight. As the nature of silane is varied, the rate of polymer formation varies, the silane with the most electron-deficient silicon giving the greatest rate. Molecular weight is constant as diol is changed but varies when the silane is changed so that the silane with the most bulky substitutes will give polymer with the lowest molecular weight. The results are consistant with a S_N2 type reaction mechanism.     

A Novel Low Solvent Method for Grafting Polyaniline to Silylated Silica

Summary: Silica gel, an important inorganic polymer with many applications, was silylated with 3-(phenylaminopropyl)trimethoxysilane (PAPTMOS) by means of a novel “low solvent” method, whereby the silane was dissolved in a small amount of methanol, mixed with silica and reaction carried out in a heated vacuum oven. Polyaniline (PANI) was grafted to the silylated silica by in situ polymerization of aniline, then dedoped with aqueous ammonia. Physically adsorbed PANI was removed from the modified silica by washing with tetrahydrofuran (THF) and N-methyl-2-pyrrolidone (NMP). The silylated, PANI-modified silica had electrical conductivity 1.2 × 10⁻³ S cm⁻¹ after being re-doped with methanesulfonic acid. FTIR, elemental analysis, X-ray photoelectron spectroscopy, solid-state ¹³C and ²⁹Si NMR and morphological studies by SEM confirmed successful formation of the SiO₂-polyaniline hybrid material.