电引发丙烯腈聚合

以Pb为阴极，Pt为阳极，在特别设计的电解池阴极区内，电引发硝酸溶液中丙烯腈（AN）后聚合。动力学研究表明，聚合速度与电解电量和硝酸浓度成直线关系，与单体浓度的平方成正比。根据聚合物溶液浓度对光密度关系，认为聚合作用是由AN－HNO3络合物在阴极上俘获电子后产生的硝基丙腈自由基所引发。     

Electroinitiated Cationic Polymerization of Indene

The polymerization of indene by constant potential electrolysis in dichloromethane was achieved at low temperatures. Molecular weights were found to be inversely proportional to polymerization temperature. The oxidation peak potential of indene in the (C₄H₉)₄-NBF₄-CH₃CN electrolyte-solvent system was measured by cyclic voltammetry. Polymers which were produced electrochemically by constant potential electrolysis have the same spectral properties with those obtained by chemical methods.     

Electroinitiated Anionic Polymerization of Vinyl Monomers

Abstract

Polarographic reduction and electrolytically initiated anionic polymerization of various monomers have been investigated with tetra-n-butylammonium perchlorate in dimethoxyethane.     

Electroinitiated Cationic Copolymerization of Styrene and 4-Methoxystyrene

The copolymerization of styrene and 4-methoxystyrene by constant potential electrolysis in 1,2-dichloroethane was achieved at three different potentials. Amounts of the monomers in the resulting copolymers were found to be potential-dependent. The effect of polymerization potential on copolymer composition was also found to be related to anodic peak potentials (E_p,a) of the monomers.

Monomer reactivity ratios were found with the integrated Lewis-Mayo equation.     

Electroinitiated Polymerization of N-Vinylcarbazole by Direct Electron Transfer

Electroinitiated polymerization of N-vinylcarbazole has been accomplished by constant potential electrolysis. It was found that direct electron transfer from the monomer to the anode initiates the polymerization even at a potential as low as +0.95 V versus Ag^?/ Ag⁺. Dichloromethane was used as the solvent, and the electrolyte was tetrabutylammonium fluoroborate. Conversions as high as 86% were reached even when a microelectrode was used. Effects of electrode area, temperature, and electrode potential on polymerization were studied. Percent conversion was followed by cyclic voltammetry.     

Verdazyl-Mediated Polymerization of Styrene

Attempted controlled polymerizations of styrene, conducted in the presence of either 1,3,5-triphenyl-6-oxoverdazyl or 1,5-dimethyl-3-phenyl-6-oxoverdazyl radicals initiated with benzoyl peroxide or 1,1′-azobis(cyclohexanecarbonitrile) were universally unsuccessful regardless of the reaction temperature and the initiator/verdazyl molar ratio. No improvement was observed using a verdazyl-terminated styrene initiator adduct prepared by an exchange reaction between a styrene-TEMPO alkoxyamine and a 1,3,5-triphenyl-6-oxoverdazyl radical. However, controlled polymerizations of styrene were achieved at 125 °C using a styrene-verdazyl adduct containing the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical. Polydispersity indexes remained low throughout the polymerizations and plots of number average molecular weight ( ) versus time were linear. However, the actual values were considerably lower than theoretical, an unexpected result that is under investigation.     

Electroinitiated Polymerization of Acrylamide Using Tartaric Acid as Electrolyte

Abstract

Acrylamide has been polymerized electrochemically in aqueous medium in the presence of tartaric acid, and the effects of such reaction variables as monomer concentration, electrolyte concentration, and current on the rates of polymerization have been studied. The mechanisms of initiation and termination have been discussed in the light of the observed kinetic data. Initiation is believed to occur through the generation of radical ions during electrolysis, and electrolytic termination is found to be negligible during the polymerization process.     

Electroinitiated Polymerization of 3,3-BIS(N-Carbazolylmethyl)Oxetane

Abstract

3,3-Bis(N-carbazolylmethyl)oxetane, a cyclic compound with carbazolyl substituents closely linked to the oxetane ring, was polymerized by electrochemical initiation in aprotic polar solvents using a quaternary ammonium salt as electrolyte. Colored polymers were obtained as thin films deposited on the anode and were characterized by IR, ¹H NMR, and thermogravimetry. The data obtained refute the classical cationic polymerization of oxetanes.     

新型引发剂引发苯乙烯聚合的动力学

采用过氧化2-乙基己基碳酸叔丁酯为引发剂,研究了苯乙烯自由基本体聚合的动力学过程,考察了引发剂浓度、温度、乙苯质量分数对聚合反应速率和聚苯乙烯分子量的影响.结果表明:在117℃下,聚合速率(Rp)对引发剂浓度的反应级数为0.42,对苯乙烯浓度的反应级数为1,聚合反应的表观活化能为54.8 kJ/mol.引发剂浓度、温度、乙苯质量分数的提高导致聚苯乙烯数均分子量分别下降了约30％、20％和15％,其中引发剂浓度的影响最为显著.     

苯乙烯微乳液种子聚合

通过观测苯乙烯微乳液种子聚合前后体系内聚合物粒子大小及其分布的变化发现,无论是γ射线还是KPS引发,聚合过程中都没有新的聚合物粒子生成。尽管聚合前体系中存在单体溶胀的胶束,但在聚合过程中这些胶束主要充当单体仓库,自己成核聚合的几率很低。由于微乳液种子聚合体系内,单体量相对较低,聚合物粒子数目很大,其聚合动力学明显不同于常规乳液种子聚合。     

Radiation-Induced Polymerization of Styrene Oxide

Radiation-induced polymerization of styrene oxide in the liquid and solid states was carried out by initiating with γ-rays from ⁶⁰Co and electrons from a Van de Graaff accelerator.

Effects of dose rate, a radical inhibitor, and temperature on the polymerization were examined. Infrared spectra and viscosities of polymers obtained were measured.

From these experiments, the following results were obtained:

1. Apparent activation energies are 6.2 kcal/mole for the liquid-state polymerization and 0.17 kcal/mole for the solid-state polymerization, respectively.

2. The polymerization in liquid state is inhibited and retarded by p-ben-zoquinone.

3. The rate of polymerization is approximately proportional to the dose rate.

4. The viscosity of polymers obtained increases with irradiation dose.

5. Infrared spectrum of polymers obtained varies with the polymerization temperature.

It is emphasized in this paper that the chain-transfer and isomerization reactions are rapid and play an important role in the polymerization of styrene oxide, and that the polymer-forming process is not so rapid, owing to a step-by-step type of growing.     

Polymerization Processes in Ionic Liquids. Cationic Polymerization of Styrene

There is an increasing interest in using ionic liquids as solvents for polymerization processes. Most published data deals with controlled radical polymerization. It has been shown that ionic liquids offer several advantages for conducting Atom Transfer Radical Polymerization (ATRP), such as good solubility of catalyst and improved k_p/k_t ratio. Ionic liquids are highly polar therefore they seem to be suitable solvents for conducting also ionic polymerization processes. In our preliminary communication we reported on cationic polymerization of styrene initiated by R-Cl/TiCl₄ system in ionic liquid. To clarify the mechanism of this process, racemization of optically active 1-phenylethyl choride (initiator and the model of dormant species) was studied and it was shown that in ionic liquid racemization proceeds even in the absence of coinitiator (TiCl₄). Because racemization proceeds through ionization of C Cl bond, this explains the cationic polymerization of styrene initiated by R-Cl alone (in the absence of coinitiator). Chain transfer, however, cannot be eliminated, therefore polymerization is not controlled.     

Model Development in Thermal Styrene Polymerization

Summary: The thermal polymerization of styrene is usually modeled by relying on a reaction scheme and a set of equations that were developed more than three decades ago by Hui and Hamielec. Many detailed models of styrene polymerization are available in the open literature and they are mostly based on the work of Hui and Hamielec, which nearly makes this the standard to follow in explaining the behavior of polystyrene reactors. The model of Hui and Hamielec does a very nice job of describing monomer conversion data but discrepancies are seen between observed and predicted values of number and weight average molecular weights, M_n and M_w. Discrepancies in number average molecular weight seem to be the result of random noise. Discrepancies in weight average molecular weight grow as the polymerization temperature decreases and some of the trends observed in the residuals over the entire temperature range cannot be attributed to random noise. Hui and Hamielec attributed the observed deficiencies to a standard deviation of ±10% in their GPC measurements. A new data set with an experimental error of 2% for average molecular weights is presented. The set contains measured values of M_n, M_w and M_z, so the polymerization scheme has been extended to include third order moments. The data set also includes the effect of ethylbenzene as a chain transfer agent. We present the results of comparing model predictions to our measurements and the adjustments made in the original set of kinetic parameters published by Hui and Hamielec.     

苯乙烯间规聚合进展

苯乙烯间规聚合在近１０年来得到迅速的发展。本文将综述用于苯乙烯间规聚合的催化剂、助催化剂以及聚合机理。     

Anionic Polymerization of Styrene in Binary Solvents

Experimental findings on the triple ion formation were examined by adopting more elaborate purification method for solvents. For polystyryllithium in dimethoxyethane (DME) and benzene mixtures, the overall rate constant of propagation (k_p) was confirmed to increase with increasing living end concentration under some conditions, in contrast with cases for polystyryllithium in tetrahydrofuran-benzene mixtures and for polystyryl sodium, potassium and cesium in DME-benzene mixtures. The propagation by the inter-molecular triple ions proposed earlier in order to elucidate the kinetic “anomaly” mentioned above was briefly discussed.     

微乳液催化苯乙烯聚合反应

微乳液催化苯乙烯聚合反应１）郝京诚汪汉卿２）（中国科学院兰州化学物理研究所兰州７３００００）石元昌李干佐（山东大学胶体与界面化学研究所济南２５０１００）关键词微乳液催化苯乙烯聚合微乳液［１］是油、水、表面活性剂和助表面活性剂在适当比例下自发形成的热力...     

Parameter Selection and Estimation Techniques in a Styrene Polymerization Model

Styrene polymerization literature is reviewed and a model with dicumyl peroxide and benzoyl peroxide initiators is developed. Nine parameters are selected for estimation using statistical methods that account for the influence of parameters on model predictions, correlated effects of parameters and uncertainties of initial literature values. Updated parameters result in improved fits to conversion and molecular weight data from three research groups, reducing the least‐squares objective function by 73%. Use of industrial data from 19 batch reactor runs increases the number of estimable parameters to 16. Good predictions are obtained for validation runs with temperature ramps using both initiators.

     

Polymerization of Styrene in the Presence of a 1,3-Dipolar Compound

Free-radical polymerization of styrene initiated by α,α¹ -azobisiso-butyronitrile (AIBN) has been studied in the presence of a 1,3-dipolar compound (methylnitrile ylide, MNY) by a dilatometric technique. The MNY retards the reaction by decreasing the rate of propagation and increasing the energy of activation. Polar solvents have very little influence on the rate of polymerization, but non-polar solvents favor retardation. MNY has no influence on the average degree of polymerization, and the system attains a steady state.     

Atom Transfer Radical Polymerization of Styrene Using a Bifunctional Initiator

A bifunctional alkyl halide, namely l, 2-bis(2′-bromobutyryl) ethane (BBrBE), was synthesized and used to initiate the bulk atom transfer radical polymerization (ATRP) of styrene (St) at 110°C in the presence of CuBr/2,2′-bipyridyl. The narrow polydispersity of polystyrene (PSt) with precisely two arms could be synthesized. The initiate ability of the two active bromide functional groups at both sides of BBrBE for St and the propagation ability of the two arms were confirmed to be similar by the characterization of the individual arms obtained upon hydrolysis of the ester link between the core and the branches.     

Styrene Miniemulsion Polymerization: Incorporation of N-Alkanes

Summary: In this work, the incorporation of alkane hydrocarbons in poly(styrene-co-methacrylic acid) particles via miniemulsion polymerization was investigated. The reactions were performed at 80 °C for 4 hours, using benzoyl peroxide as oil-soluble initiator. The effects of different concentrations of a hydrophilic co-monomer (methacrylic acid) and different types and concentrations of alkanes, namely n-hexadecane, n-octane and n-heptane were evaluated. Miniemulsion stability at room temperature and reaction kinetics were monitored, as well as the particles size and morphology. Results show the viability of encapsulation of alkanes in miniemulsion polymerizations, especially of alkanes with intermediate chain lengths (e.g. n-hexadecane). When short chain alkanes are incorporated the miniemulsions become less stable, due to their lower hydrophobicity. Based on monomer droplet size distribution data, it was determined that the best concentration of hydrophilic co-monomer for the studied system was 1.0 wt%.