Zur Kinetik der stabilisierten Fällungs-polymerisation eines Kationischen Monomeren in wäßrigen Natriumchlorid-Lösungen

The stabilized free-radical precipitation polymerization of the cationic monomer N-(2-methacryloyloxyethyl)-N,N-dimethylbenzylammonium chloride (MADAMBQ) in aqueous solutions of sodium chloride was studied by reaction calorimetry. Poly(ethylene oxide) was used as stabilizer. The rate of polymerization reaches its maximum immediately after initiation and remains nearly constant up to 50 % conversion followed by a decrease that could be described by a first order kinetics. The particles formed are approximately 1 to 30 μm in diameter and are stable over a period of several months. A model based on the theory of homogeneous particle nucleation is suggested to describe the kinetic course of polymerization, taking into account the rate of polymerization in both phases. With the assumption that the concentration of monomer in the phases is determined by a Nernst distribution law, the kinetics of the early stage of polymerization can be modelled reasonably well. The solution polymerization and the unstabilized precipitation polymerization of MADAMBQ was also studied.     

Esterification of hydroxylated polymers with 2-sulfobenzoic acid cyclic anhydride: A facile approach for the synthesis of near-monodisperse strong acid homopolymers and diblock copolymers

A convenient two-step route was developed to prepare a range of low polydispersity strong acid homopolymers and several examples of well-defined diblock copolymers. Atom transfer radical polymerization (ATRP) of either 2-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate or glycerol monomethacrylate afforded the corresponding near-monodisperse hydroxylated homopolymers, while several diblock copolymer precursors were prepared by either (1) the one-pot ATRP of 2-hydroxypropyl methacrylate and 2-(diethylamino)ethyl methacrylate using sequential monomer addition or (2) the ATRP of either 2-hydroxypropyl methacrylate or glycerol monomethacrylate using a poly(ethylene oxide)-based macro-initiator. Excess 2-sulfobenzoic acid cyclic anhydride was used to fully esterify the hydroxy groups of these homopolymers and diblock copolymers under mild conditions. The resulting zwitterionic diblock copolymers undergo micellar self-assembly on adjusting the pH of the solution, while one of the anionic poly(ethylene oxide)-based diblock copolymers formed colloidal polyelectrolyte complexes in aqueous solution when mixed with a cationic poly(ethylene oxide)-based diblock copolymer.     

Influence of molecular dipole on monoacrylate monomer reactivity

Numerous acrylate monomers have been synthesized and evaluated extensively as a means to explore the relationship between molecular polarity and monomer reactivity. Various monomers, characterized by high values of dipole moment, were polymerized in bulk, and no correlation of dipole moment to monomer reactivity was established. Solution polymerization studies were performed on phenyl carbamate ethyl acrylate and several substituted derivatives to observe the effects of changing solvent polarity on the polymerization kinetics. The results of solution polymerization studies indicated that traditional dilution effects, which suppress the polymerization kinetics, dominate the reactions. Changes in solvent polarity had minimal impact on the polymerization kinetics.     

Cure properties of epoxies with varying chain length as studied by DSC

The cure of diglycidyl ether of bisphenol A (DGEBA) and a homologous series of poly(ethylene oxide) diglycidyl ether (PEODE) epoxy resins with 4,4′‐diaminodiphenyl sulfone (DDS) was studied by scanning and isothermal differential scanning calorimetry (DSC). The heat of polymerization was relatively independent of monomer structure and chain length when determined by isothermal DSC. Variations in the heats of polymerization determined by the scanning method were attributed to degradative reactions at higher temperatures during the scan. The activation energies determined by scanning DSC experiments were relatively constant at 61 ± 3 kJ/mol. However, using an isothermal cure method, the activation energies were found to vary with monomer structure and extent of cure. The isothermal kinetics were analyzed in terms of the autocatalytic model on the basis of competing reaction paths involving catalysis by either initial impurities or hydroxyl groups produced in situ. The activation energies of both reaction paths were found to vary with monomer structure and degree of conversion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1479–1488, 1999     

Kinetic study for the decay rate of ethylene polymerization catalyzed over silica supported TiCl4/MgCl2 catalysts

The kinetics for decay rate of ethylene polymerization catalyzed with TiCl₄/MgCI₂/Si0₂ has been investigated in the range of temperatures between 40 and 90°C and in the range of ethylene pressures between 4 and 12.4 atm. The decay of polymerization rale was fitted well by the type of first order decay. The decay rale constant caused by monomer could be expressed by k _d ^/′ = C ·[M]^−1/2. Some plausible speculations have been proposed on the deactivation mechanism caused by monomer. The activation energy for the deactivation reaction is 9.8 kcal/mole.     

Monodisperse micron-sized polystyrene particles by seeded polymerization using reactive macrosurfactants

Monodisperse micron-sized polystyrene particles could be prepared through a two-staged seeded swelling and polymerization method using reactive surfactants. The seed was obtained by emulsifier-free emulsion polymerization. To prepare conventional surfactant-free monomer emulsion droplet in swelling process, a tri-block diol diacrylate (t-BDDA), which is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer containing two chain ends capped with acryloyl chloride, was employed as a reactive surfactant instead of conventional surfactants. Thermodynamic consideration of the effect of monomer droplet size and interfacial tension on the swelling process ensured that two-staged monomer swelling could be effectively performed by using t-BDDA as a surface-active macromonomer. From the surface tension measurement and optical microscope observation, it was found that the t-BDDA had a favorable surface activity when the monomer emulsion was prepared under its cloud point. From the X-ray photoelectron spectroscopy, it was found that most of the t-BDDA resided on the final particle surfaces.     

Ring-opening polymerization of 2,2-dimethyltrimethylene carbonate using imidazol-2-ylidenes

The ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) catalyzed with imidazol-2-ylidenes substituted by benzyl, isopropyl, and methyl was conducted. The influences of substitutional group, monomer, catalyst, and initiator (benzyl alcohol) concentration, as well as polymerization temperature and reaction time were investigated in detail. The kinetics studies indicate that the polymerization rate is first-order with respect to both monomer and catalyst concentrations. The overall activation energy amounts to 51.06 kJ/mol. Mechanistic studies reveal that the 2,2-DTC polymerization proceeds according to a monomer-activated process.     

以聚乙烯醇为保护胶体的乳液与部分官能团的接枝反应研究

主要研究了在以聚乙烯醇为保护胶体的醋酸乙烯乳液聚合中,乳液与环氧丙烯酸酯、聚氨酯、硅烷等官能团的接枝反应.在以过硫酸铵为引发剂、以聚乙烯醇为保护胶体的醋酸乙烯乳液聚合中,乳液与上述各类官能团间发生的接枝反应直接影响乳液的黏度、固体含量、剪切强度等宏观性质.研究发现官能单体脂肪醇聚氧乙烯醚、丙烯酸异辛酯(2-EHA)等单体和丙烯酸(AA)与乙烯基三乙氧基硅烷共同作用时对乳液的宏观性质影响显著.     

二甲氨基链中多官能化溶聚丁苯橡胶的合成

采用负离子溶液聚合法,以仲丁基锂为引发剂、环己烷为溶剂、四氢呋喃为结构调节剂,以及1,1-双（4-二甲基氨基苯基）乙烯为官能化共聚单体与丁二烯和苯乙烯进行活性负离子共聚合,制备了二甲氨基链中多官能化丁二烯-苯乙烯共聚物,考察了聚合温度和结构调节剂用量对聚合动力学和聚合物微观结构的影响。结果表明,共聚物链中二甲氨基官能团数量可通过调整聚合温度和结构调节剂用量进行准确控制,随聚合温度升高和四氢呋喃用量的增加,单体的总反应速率和转化率都逐渐增大;聚合物中1,2-结构的含量随结构调节剂用量的增加而逐渐增大,随聚合温度升高而逐渐减小。求得聚合温度为50 ℃时丁二烯和苯乙烯单体的平均竞聚率为69.67。     

三齿配体过渡金属烯烃聚合催化剂研究新进展

介绍了三齿配体结构、中心金属原子、助催化剂、负载化等对催化剂性能的影响;综述了三齿配体过渡金属烯烃聚合催化剂在乙烯齐聚、乙烯聚合、丙烯聚合以及极性单体聚合方面的应用以及三齿配体过渡金属烯烃聚合催化剂的催化机理方面的研究进展。     

Semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion

The semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion was studied under the condition of no seed particles used in polymerization system. Concentration of emulsifier was set above critical micelle concentration. Effect of monomer feed rate on the chemical kinetics, average particle size and distribution and on the polymer molar mass and distribution was investigated. During monomer addition, polymerization rate was constant and controlled by the monomer feed rate. According to the proposed mechanism for anionic polymerization in emulsion, it was assumed that also the number of active polymerization sites and monomer concentration at the particle surface, where propagation occurs, remain constant. A continuous increase of average particle size and absence of extensive condensation reactions at high conversion suggested that the freshly added monomer diffuses toward hydrophobic polymer particles, where it is consumed in propagation reaction and/or accumulated in the particle core.     

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Cationic polymerization of ethylene oxide with Maghnite‐H as a clay catalyst in the presence of ethylene glycol

The activated‐monomer cationic ring‐opening polymerization of ethylene oxide, initiated with ethylene glycol and using an acid‐exchanged montmorillonite clay called Maghnite‐H⁺ as an effective catalyst, was carried out to obtain the corresponding homopolymers with narrow polydispersity ratios. The molecular weights of the obtained polymers were controlled with the feed ratio of the monomer to the initiator. The effects of the amount of the catalyst and time on the polymerization yield and viscosity of the polymers were studied. The structure was confirmed with proton nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The hydrolytic polymerization of ε-caprolactone by triphenyltin acetate

The polymerization of ε-caprolactone (CL) using triphenyltin acetate has been investigated. Polymers with broad MWD were obtained in almost quantitative yield. After an initial induction period, the polymerization showed zero order kinetics with respect to monomer and nearly first order with respect to catalyst. The mechanism of the propagation reaction is proposed to proceed via an ester alcoholysis, with initiation by traces of water. The zero order kinetics are explained as follows: the tin catalyst is coordinated by the cyclic lactone, monomer addition to the polymer chain in the rate-determining step results in formation of an acyclic ester link, which is no longer a strong donor, and leads to a coordinatively unsaturated tin species.     

多官能度聚乙二醇的合成研究

以D-山梨醇为引发剂,二甲亚砜为溶剂,氢氧化钾为催化剂,环氧乙烷为单体,阴离子开环聚合合成了多官能度聚乙二醇。详细考察了催化剂、引发剂、溶剂、聚合温度等因素对聚合产物的性能影响。初步确定了聚合条件,聚合温度100～110℃,聚合时间6h。通过官能度的理论计算和测试证明合成的聚合物为多官能度聚乙二醇。     

Poly(dimethylsiloxane‐b‐styrene) diblock copolymers prepared by reversible addition‐fragmentation chain transfer polymerization: Kinetic model

Well‐defined polydimethylsiloxane‐block‐polystyrene (PDMS‐b‐PS) diblock copolymers were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a functional PDMS‐macro RAFT agent. The RAFT polymerization kinetics was simulated by a mathematical model for the RAFT polymerization in a batch reactor based on the method of moments. The model described molecular weight, monomer conversion, and polydispersity index as a function of polymerization time. Good agreements in the polymerization kinetics were achieved for fitting the kinetic profiles with the developed model. In addition, the model was used to predict the effects of initiator concentration, chain transfer agent concentration, and monomer concentration on the RAFT polymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetics of phthalic anhydride/ethylene carbonate reactions

The kinetics of the polymerization of phthalic anhydride with ethylene carbonate to give poly(ethylene phthalate) were studied to elucidate the reaction mechanism. Zero-order kinetics were observed to varying degrees of reaction depending upon reaction temperature. Although no clear-cut overall reaction order could be established, previously proposed mechanisms involving decomposition of the carbonate as the first step of the reaction were ruled out. The chain propagation step was on the order of or faster than the initiation step of the reaction. Virtually no ether–glycol species were formed during the polymerization. A new mechanism was proposed for the polymerization.     

Die mit Natriumphenolat katalysierte Addition von Äthylenoxid-Propylenoxid-Gemischen an Monophenylmonoalkylenglykole. II. Die Kinetik der Äthylenoxid-Propylenoxid-Addition an Monophenylmonoäthylenglykol

The dependence of insertion-type addition of ethylene oxide/propylene oxide mixture to monophenyl monoethylene glycol on monomer ratios was investigated. An attempt to determine the reactivity parameters by MAYO and LEWIS method was discarded on account of differing dimensions shown by the rate constants of separate reactions. A rate law to describe the consumption of ethylene oxide has been presented. The dependence of relative reaction rates on the-mole ratios shows preference for addition of ethylene oxide; however, rise in reaction temperature exercises no appreciable effect on the preferred addition.     

Recent Research Progress of Branched and Functional Branched Polyethylene Prepared Using Ni- and Pd–Based Catalysts

In this paper, the recent development of branched and functional branched polyethylene prepared using Ni- and Pd-based catalysts are reviewed. The influence of ligand species, steric effect, electronic effect and polymerization condition on branching density of resultant polymer prepared using Ni- and Pd-based catalysts is discussed. In addition, the review is also focused on functional branched polyethylene produced by copolymerization of ethylene and polar monomer and copolymerization mechanism.     

Adhesion enhancement in waterborne acrylic latex binders synthesized with phosphate methacrylate monomers

The effect of the addition of a phosphoric acid group containing monomer on polymerization kinetics, copolymer microstructure and end-use properties of a latex prepared by seeded emulsion polymerization of MMA/BA/MAA/AAEMA/SIPOMER PAM100 was studied. It was found that despite of the surface activity of the phosphated monomer, the polymerization kinetics was not affected. Gel content increased with the concentration of phosphate monomer due mainly to the presence of divinyl ester phospate impurities. Gel improved the chemical resistance of the latex films. However, the most affected property was adhesion. Increasing amounts of the phosphated monomer led to a strong enhancement of the adhesion due to chemical interactions established with the metal surface. It was also found that the feeding strategy of the phosphated monomer played an important role in the adhesion enhancement. Latexes synthesized using a delayed addition of the phosphate monomer showed better performance than latexes prepared following a conventional addition strategy. The latexes synthesized during the investigation were evaluated as binders in a primer formulation. A primer with good adhesive and corrosion resistance properties was achieved using a 5 wt.% of the phosphated monomer.