Phase‐equilibrium behavior of vinyl chloride/n‐butane and its application in determination of vinyl chloride heterogeneous polymerization kinetics

Studies of the phase‐equilibrium behavior of vinyl chloride (VCM)/n‐butane mixtures and the kinetics of VCM heterogeneous polymerization, using n‐butane as a reaction medium, were carried out using a 1‐L glass autoclave. The vapor composition was measured by gas chromatography, showing that the vapor pressure of the VCM/n‐butane mixture was located above the line connecting the points for pure VCM and n‐butane. The concentration of VCM in the vapor phase was greater than that in the corresponding liquid phase. It was confirmed that the presence of poly(vinyl chloride) (PVC) resin had no significant influences on the phase equilibrium of VCM/n‐butane mixtures. Thus, the phase‐equilibrium equations were applied to determine the conversion of VCM during heterogeneous polymerization. The conversions calculated from the variations of vapor pressure or composition agreed with those determined by the weighing method. The conversion–time and polymerization rate–time curves obtained for VCM heterogeneous polymerization showed that the polymerization accelerated at low initiator concentration, but the polymerization rate decreased with an increase of conversion at relatively high initiator concentrations. The chain‐transfer reaction to n‐butane was confirmed by a decrease of the molecular weight and broadening of the molecular weight distribution of PVC. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2179–2188, 2001     

Swelling of PVC latex particles by VCM

The uptake of VCM by PVC particles prepared by emulsion polymerization at various temperatures, the solubility of VCM in water and the density of VCM vapour have been studied between 15 and 60°. The swelling of PVC by VCM was almost independent of temperature. The solvent interaction parameter, x, calculated according to the Flory-Huggins equation, was strongly dependent on polymer concentration and showed a maximum value. The maximum uptake of VCM depended on the temperature of polymerization. PVC samples prepared at 11, 50 and 90° showed maximum uptakes of 0.22, 0.29 and 0.37 kg VCM/kg PVC respectively. The influences of particle size and emulsifier concentration have been studied. The results indicate that VCM is solubilized in the surface layer of adsorbed emulsifier.     

Calculation and Applications of VCM Distribution in Vapor/Water/Solid Phases during VCM Polymerization

The distribution of vinyl chloride monomer (VCM) in vapor, water, swollen polymer, and free monomer phases as a function of conversion of VCM can be calculated from the related partition coefficients. It was found that the amount of monomer in the vapor and water phases is particularly significant, being 20% (at 60°C) of that in the polymer phase at the peak exotherm. Neglecting the VCM dissolved in water and that in the head space of the reactor would seriously overestimate the polymerization rate and overdesign the required cooling capacity of the reactor. From the distribution the relation between conversion (x) vs pressure (P) after the pressure starts to drop can be developed and used to determine conversion at termination by pressure measurement. The results of ×vs P from our partition coefficient approach are consistent with those derived from Flory-Huggin's equation. Also the knowledge of VCM distribution at termination of the polymerization will assist VCM accountability and stripper design.     

Emulsion synthesis of nanoparticles containing PEDOT using conducting polymeric surfactant: Synergy for colloid stability and intercalation doping

Poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is a widely used conductive aqueous dispersion synthesized by using emulsion polymerization method. To further enhance its solution processability and conductivity of PEDOT derivatives, we proposed to replace the nonconductive PSS with conductive poly[2‐(3thienyl)‐ethoxy‐4‐butylsulfonate] (PTEB) as surfactant for the emulsion polymerization of PEDOT. The reaction involved colloid stabilization and doping in one step, and yielded PEDOT:PTEB composite nanoparticles with high electrical conductivity. Contrary to its counterpart containing nonconductive surfactant, PEDOT: PTEB showed increasing film conductivity with increasing PTEB concentration. The result demonstrates the formation of efficient electrical conduction network formed by the fully conductive latex nanoparticles. The addition of PTEB for EDOT polymerization significantly reduced the size of composite particles, formed stable spherical particles, enhanced thermal stability, crystallinity, and conductivity of PEDOT:PTEB composite. Evidence from UV–VIS and FTIR measurement showed that strong molecular interaction between PTEB and PEDOT resulted in the doping of PEDOT chains. X‐ray analysis further demonstrated that PTEB chains were intercalated in the layered crystal structure of PEDOT. The emulsion polymerization of EDOT using conducting surfactant, PTEB demonstrated the synergistic effect of PTEB on colloid stability and intercalation doping of PEDOT during polymerization resulting in significant conductivity improvement of PEDOT composite nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2536–2548, 2008     

Novel copolymers via nitroxide mediated controlled free radical polymerization of vinyl chloride

Controlled free radical polymerization (CFRP) of vinyl chloride (VCM) and copolymerization with several comonomers have been studied in aqueous suspension. Therefore di-tert-butylnitroxide and three novel nitroxyl radicals were used as mediating agents. Copolymerization of VCM with styrene, partly combined with acrylonitrile, maleic acid anhydride and maleic acid imide as well as methyl methacrylate, n-butyl methacrylate, butyl acrylate and butadiene have been achieved, demonstrating an efficient route for novel vinyl chloride copolymer architecture.     

Encapsulation of β-cyclodextrin by in situ polymerization with vinyl chloride leading to suppressing the migration of endocrine disrupting phthalate plasticizer

We performed the encapsulation of β-cyclodextrin (β-CD) in PVC by in situ polymerization with vinyl chloride monomer (VCM), and investigated the effect of CD encapsulation on the suppression of dioctyl phthalate (DOP) migration suspected as endocrine disruptor. β-CD was partially modified with 3-(methacryloxy)propyl trimethoxysilane and modified β-CD (MCD) was then encapsulated in PVC through suspension polymerization via radical reaction between double bonds MCD and VCM. Resulting MCD-encapsulated PVC (MCD_x-PVC) exhibited the similar morphology and characteristics to commercial PVC. For MCD_x-PVCs plasticized with DOP, they showed the considerably suppressed DOP migration as well as the similar optical and mechanical properties to conventionally plasticized PVC. In particular, the plasticized MCD_x-PVCs exhibited the superior suppression of DOP migration compared to the plasticized PVC where MCD and DOP were introduced by conventional melt mixing. Therefore, the encapsulation of MCD in PVC is thought to be an effective approach to producing the ecological PVC material.     

Colloidal stability of PVC primary particles in vinyl chloride

The electrostatic contribution to the colloidal stability of PVC primary particles (R=0.15 m) dispersed in vinyl chloride, was calculated using models based on the Coulombic interactions and the DLVO theory. The calculations were based on: a) the particle charge as obtained from literature data on the electrophoretic mobility of PVC primary particles in VCM and b) on estimates of the Debye length as obtained from measurements of the electrical conductivity of VCM and of solutions of Bu₄NBF₄ in VCM.The calculations showed that particle stability would decrease with particle size (experimentally-observed behaviour), only if the particle charge increased with size at a lower rate than in proportion to particle radius.The calculations also suggest that particle growth may be governed by a competitive growth mechanism of electrostatic origin. Particle growth is assumed to occur by absorption of many small, weakly charged basic particles from the monomer phase. According to the calculations, the electrostatic interaction between primary and basic particles may be such that the growth of the smaller primary particles is favoured over that of the larger ones.     

Improved lithium exchange at LiFePO4 cathode particles by coating with composite polypyrrole–polyethylene glycol layers

The polypyrrole–LiFePO₄ composites were synthesized by simple chemical oxidative polymerization of pyrrole (Py) monomer directly on the surface of LiFePO₄ particles. Properties of resulting polypyrrole–LiFePO₄ (PPy-LiFePO₄) samples (especially conductivity) are strongly affected by the preparation technique, polymer additives, and conditions during synthesis. For increasing of PPy-LiFePO₄ conductivity, we used polyethylene glycol (PEG) as additive during polymerization. The electrochemical behavior of the samples was examined by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that PPy/PEG composite polymer decreased the particle to particle contact resistance. Impedance measurements showed that the coating of PPy/PEG significantly decreases the charge transfer resistance of LiFePO₄ electrodes.     

水介质中吡咯的电化学聚合反应

研究了扫描电位上限对循环伏安法制备聚吡咯膜性能的影响，吡咯在水溶液中于玻碳电极表面化学聚合的起始电位为0．58V，在聚吡咯（Ppy）修饰电极表面聚合的起始电位为0．55V，当聚合电位上限在0．80V以上时，Ppy的氧化还原反应可逆性变差，同时，氧化电位过高将导致Ppy膜导电性能下降；研究了聚合介质对循环伏安法制备导电聚吡咯膜的影响，实时观察了吡咯（Py）聚合过程溶液中质子含量的动态变化，发现Py聚合伴随有质掺杂←→释放过程；结合Ppy膜的元素分析、ESR分析和IR光谱分析，总结出了水介质中电化学聚合高导电性聚吡咯膜的条件。     

Calorimetric and dielectric effects during polymerization of an elastomer‐containing mixture and liquid‐liquid phase separation

Calorimetry and dielectric spectroscopy of an elastomer, amine terminated butadiene acrylonitrile (ATBN), dissolved in a stoichiometric mixture of ethylene diamine and diglycidyl ether of bisphenol‐A, were studied in real time during the polymerization and phase separation of the mixture. In the two polymer compositions containing 8 w/w % ATBN and 20 w/w % ATBN, the total enthalpy released per mole of DGEBA's reaction was the same, indicating indetectably small changes in molecular interactions before and after the phase separation. The dielectric relaxation spectra showed no evidence for phase separation, which indicated a gradual phase separation with time and the extent of polymerization, and relatively small differences in the permittivity and conductivity between the ATBN particles and the network matrix at the time of phase separation. The equilibrium permittivity and dc conductivity showed a nonideal mixing of ATBN. The stretched exponential relaxation parameter remained at 0.36, but the characteristic dielectric relaxation time and the dc conductivity increased on addition of ATBN. An increase in the temperature had a greater effect on the relaxation time than the increase in the extent of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1911–1919, 1999     

Monitor of Polymerization of Inverse Microemulsions Containing Methyl Methacrylate and Acrylic Acid

Microemulsions are isotropic, optically transparent and thermodynamically stabledispersion systems consisting of water, oil and suitable surfactants. Polymerization inmicroemulsions has been widely studied since 1980s, which can be divided intooil-in-wate…     

Effect of reaction medium on ionic lactam polymerization

Ring-size and substitution greatly affect the permittivity and donor-acceptor properties of lactams and their derivatives as well as of the corresponding polymers. Permittivity changes occurring during bulk polymerization affect dissociation equilibria and the very high increase in permittivity during polymerization is responsible for the autoacceleration observed in the anionic polymerization of the seven-membered lactam. In diluted solution, pronounced effects of the nature of solvent or additive have been observed in anionic polymerization of substituted four-membered lactams. Whereas the initial rate of polymerization is independent of the monomer concentration, the apparent order in the monomer increases and the rate of polymerization in most solvents decreases during polymerization, except in solvents of very low polarity. Changes of permittivity and conductivity during and after polymerization indicate, that changes in the solvation and rearrangement of the growth center are responsible for its varying activity. These processes increase the reactivity during ageing of the living system. Similarly to other heterocyclic monomers, the cationic polymerization of N-acyllactams is rather insensitive to the permittivity of the reaction medium.     

Electrophysical properties of metal nitrate complexes with polyacrylamide

The electrophysical characteristics of metallopolymers obtained by spontaneous polymerization of complexes of Er, Ca, and UO₂ nitrates with acrylamide were investigated. The conductivity () at direct current was measured (10^–5 to 10^–6 Ohm^–1 cm^–1), and its alterations during the polymerization were observed. The conductivity of the metallopolymers obtained depends essentially on the voltage applied during the polymerization and the component ratio in the original mixture. It is concluded that the conductivity is ionic in character. The conductivity and the electret properties discovered depend on the moisture content of the samples.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 865–867, May, 1994.     

Polypyrrole-coated natural rubber latex by admicellar polymerization

Admicellar polymerization has been used for the preparation of an electrically conductive polypyrrole coating on latex particles. An anionic surfactant, sodium dodecyl sulfate (SDS), was adsorbed onto natural rubber (NR) latex particles to form the surfactant bilayers after adjusting the pH below the point of zero charge of the latex surface. Adsorption of SDS and pyrrole adsolubilization were determined as a function of pyrrole and sodium chloride concentrations. Pyrrole caused a decrease in SDS adsorption at equilibrium. Sodium chloride increased the surfactant adsorption and the pyrrole adsolubilization. Thermogravimetric results showed the presence of polypyrrole. The conductivity of the polypyrrole-coated NR latex film prepared by admicellar polymerization without salt was the lowest; however, with salt addition, the conductivity of the film improved significantly. The oxidative polymerization technique resulted in a relatively higher conductivity than oxidative admicellar polymerization.     

Preparation and reactivity of metal-containing monomers

Homo- and copolymerization of vanadium-containing monomers (VCM) have been studied. Radical homopolymerization of VCM is accompanied by some side reactions, such as monomer disproportionation, copolymerization with ligandin situ, cyclopolymerization, V⁵⁺V⁴⁺ reduction,etc. These reactions complicate the interpretation of the results obtained. The character of radical copolymerization of VCM with styrene or acrylonitrile is preferably radical complex. Catalytic properties of vanadium-containing homo- and copolymers (in combination with organoaluminum compounds as cocatalysts) in Ziegler-Natta ethylene polymerization have been studied. It has been shown that the products inherit the properties of immobilized polymer catalysts.For Part 39, seeIzv. Akad. Nauk, Ser. Khim., 1994, 1047 [Russ. Chem. Bull., 1994, 43, 983 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2139–2144, December, 1994.     

Physical aspects of network polymerization from calorimetry and dielectric spectroscopy of a triepoxide reacting with different monoamines

Calorimetry and dielectric relaxation spectroscopy were used to study the evolution of molecular dynamics during the isothermal polymerization of two stoichiometric mixtures of a molecule with three epoxide groups with (i) aniline and (ii) 3-chloroaniline, whose dipole moments as well as the degrees of steric hindrance to chemical reactions differ. The heat evolved on polymerization was used to calculate the number of covalent bonds formed at any instant during the polymerization reaction. The approach of the DC conductivity towards a singularity as the reaction progressed agrees with the Flory-Stockmayer theory of connectivity at gelation and not the percolation theory. It is demonstrated that a plot of DC conductivity against the extent of reaction does not have the same shape as the plot against the time of reaction. The permittivity and loss spectra obtained for structural states containing a fixed number of covalent bonds could be described by equations analogous, but not equivalent to, or the same as, the equations used for describing the dielectric properties measured for a fixed frequency during the growth of a macromolecule's network structure. For a fixed temperature, the relaxation time of the structure formed increased as the exponential of the extent of reaction (raised to the power > 1) increased. Comparative parameter-fits to the spectra showed that the DC conductivity and interfacial polarization alter the shape of the dielectric spectra such as to make misleadingly alternative parameter fits possible. The decrease of the equilibrium dielectric permittivity on polymerization is attributed to a decrease in the dipolar orientational correlation as well as the net dipole moment on increase in the number of covalent bonds. The configurational entropy decreased with increase in the number of covalent bonds formed in a manner that differs from the decrease on cooling, and a formalism relating the two effects is given. As the network structure grew isothermally, a second, high-frequency relaxation process came into evidence. This relaxation is attributed to the availability and growth of local regions of low density and high density in the network structure of the macromolecule. A number of issues of a fundamental nature that have risen since our earliest report on this subject have been elaborated and analytically clarified. © 1997 John Wiley & Sons, Inc.     

Linezolid and Vancomycin Decrease the Therapeutic Effect of Methylene Blue‐Photodynamic therapy in a Mouse Model of MRSA Bacterial Arthritis

We previously reported that photodynamic therapy (PDT) using intra‐articular methylene blue (MB) could be used to treat arthritis in mice caused by bioluminescent methicillin‐resistant Staphylococcus aureus (MRSA) either in a therapeutic or in a preventative mode. PDT accumulated neutrophils into the mouse knee via activation of chemoattractants such as inflammatory cytokines or chemokines. In this study, we asked whether PDT combined with antibiotics used for MRSA could provide added benefit in controlling the infection. We compared MB‐PDT alone, systemic administration of either linezolid (LZD) alone or vancomycin (VCM) alone or the combination of PDT with either LZD or VCM. Real‐time noninvasive imaging was used to serially follow the progress of the infection. PDT alone was the most effective, whereas LZD alone was ineffective and VCM alone showed some benefit. Surprisingly the addition of LZD or VCM reduced the therapeutic effect of PDT alone (P < 0.05). Considering that PDT in this mouse model stimulates neutrophils to be antibacterial rather than actively killing the bacteria, we propose that LZD and VCM might inhibit the activation of inflammatory cytokines without eradicating the bacteria, and thereby reduce the therapeutic effect of PDT.     

Systematic study on chemical oxidative and solid‐state polymerization of poly(3,4‐ethylenedithiathiophene)

Systematic research on the synthesis, chemical oxidative polymerization of 3,4‐ethylenedithiathiophene (EDTT) in the presence of surfactants or not, and solid‐state polymerization of 2,5‐dibromo‐3,4‐ethylenedithiathiophene (DBEDTT) and 2,5‐diiodo‐3,4‐ethylenedithiathiophene (DIEDTT) under solventless and oxidant‐free conditions has been investigated. Effects of oxidants (Fe³⁺ salts, persulfate salts, peroxides, and Ce⁴⁺ salts), solvents (H₂O, CH₃CN/H₂O, and CH₃CN), surfactants, and so forth on polymerization reactions and properties of poly(3,4‐ethylenedithiathiophene) (PEDTT) were discussed. Characterizations indicated that FeCl₃ was more suitable oxidant for oxidative polymerization of EDTT, while CH₃CN was a better solvent to form PEDTT powders with higher yields and electrical conductivities. Dispersing these powders in aqueous polystyrene sulfonic acid (PSSH) solution showed better stability and film‐forming property than sodium dodecylsulfate and sodium dodecyl benzene sulfonate. Oxidative polymerization of EDTT in aqueous PSSH solutions formed the solution processable PEDTT dispersions with good storing stability and film‐forming performance. Solvent treatment showed indistinctive effect on electrical conductivity of free‐standing PEDTT films. As‐formed PEDTT synthesized from solid‐state polymerization showed similar electrical conductivity, poorer stability, but better thermoelectric property than oxidative polymerization. Contrastingly, PEDTT synthesized from DIEDTT showed higher electrical conductivity (0.18 S cm^?1) than DBEDTT which showed better thermoelectric property with higher power factor value (6.7 × 10^?9 W m^?1 K^?2). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

修饰Langmuir-Blodget膜法制备聚(3,4-亚乙基二氧噻吩)薄膜结构和导电性能的研究

采用修饰Langmuir-Blodget(LB)膜法以二十烷酸(AA)LB膜为模板,通过3,4-亚乙基二氧噻吩(EDOT)单体在LB膜亲水基团间聚合,制备了二十烷酸/聚(3,4-亚乙基二氧噻吩)(AA/PEDOT)复合LB膜.UV-Vis、FTIR和XPS分析表明EDOT在多层膜中有效聚合,生成了PEDOT导电聚合物;X射线衍射(XRD)和二次离子质谱(SIMS)分析表明薄膜具有较好的层状有序结构,进一步研究发现EDOT在AA多层膜中的聚合破坏了原有LB膜的有序性,这可能与聚合过程对层状结构产生的破坏作用有关;采用四探针仪及半导体测试仪研究了薄膜导电性能,发现AA/PEDOT多层膜的电导率随处理时间的变化产生突变,这与多层膜中导电通道的"逾渗"有关,在有效导电网络连通后电导率发生了突变.测试结果还表明AA层和PEDOT层之间具有较为明显的界面,PEDOT显示出较好的定域性,薄膜具有很好的层状有序结构.     

Synthesis and Characterization of Conductive Polypyrrole/Montmorillonite Nanocomposites via One-pot Emulsion Polymerization

A series of electrically conductive polypyrrole/clay nanocomposites were synthesized in this work by using one-pot emulsion oxidative polymerization of pyrrole in the presence of unmodified clay and using DBSNa as the surfactant. The effect of surfactant on the morphological and electrical properties of PPy also were investigated and discussed in some extent. Electrical conductivity of the samples was measured by using samples in which the conductive materials was sandwiched between two Ni electrodes at room temperature. PPy/MMT nanocomposites were characterized by using XRD, TEM, TGA and DSC means of investigation. Intercalated structures were determined for the nanocomposites as confirmed by XRD and TEM studies. Electrical conductivity of the nanocomposites was measured to be dependent to the clay content, and the methods of preparation. Measurement also showed that polymerization of pyrrole monomers pre-intercalated between the clay gallery spaces of the clay led to higher conductivity for the nanocomposite in the same level of clay content. Thermal property measurements showed a lower thermal decomposition rate for the PPy/MMT nanocomposites with respect to the PPy.