Organometal-initiated polymerization of vinyl ketones. III. Polymerization of methyl isopropenyl ketone initiated by the triethylaluminum–methyl isopropenyl ketone complex

The kinetics and mechanism of the triethylaluminum–methyl isopropenyl ketone complex-initiated polymerization of methyl isopropenyl ketone (3-methyl-3-butene-2-one) in toluene have been studied over a range of temperature. Equimolar quantities of monomer and triethylaluminum were premixed to form the initiator species prior to the addition of the excess monomer for polymerization. Initial and overall reaction rates indicate a first-order dependence on monomer and initiator concentrations. The overall activation energy for the polymerization is 52 ± 3 kJ/mole. Molecular weight distributions were bimodal, with peaks corresponding to the trimer and high molecular weight material. The kinetic data are consistent with a coordinate polymerization mechanism.     

Free-radical polymerizations initiated by triethylaluminum–cuprous chloride mixtures

Methyl methacrylate was polymerized by triethylaluminum—cuprous chloride catalyst. A study of the polymerization kinetics indicated that the overall rate was represented by the equation, R_p = K[AlEt₃] [CuCl]^½ [M]². The overall activation energy was 16.5 kcal/mole. From ESR measurement and the results of copolymerization of methyl methacrylate with styrene, it was suggested that the catalytic system has the character of a radical initiator. A polymerization scheme was also proposed.     

Vinyl polymerization initiated by peroxydiphosphate. VII. Polymerization of acrylonitrile initiated by peroxydiphosphate–ascorbic acid redox system

The polymerization of acrylonitrile was studied with a peroxydiphosphate–ascorbic acid redox system as the initiator. The rate of polymerization increased with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. It also increased with increasing monomer concentration and the monomer exponent was computed to be unity. The reaction was carried out at three different temperatures and the overall activation energy was computed to be 4.6 kcal/mol. The effect of certain surfactants on the rate of polymerization was investigated and a suitable kinetic scheme is described.     

芳氧基钇在DMF中引发丙烯腈聚合的动力学研究

用单组分三(2,6-二叔丁基4甲基苯氧基)钇配合物[Y(OAr)3]引发丙烯腈聚合,发现介质对聚合反应的影响很大,在介电常数较大的极性溶剂N,N-二甲基甲酰胺(DMF)中,AN聚合反应的活性较高,在50℃下聚合3h,丙烯腈聚合反应转化率达到94%,所得聚丙烯腈(PAN)含52%间规结构.在DMF中聚合反应速率与单体、引发剂的浓度分别呈一级关系,丙烯腈聚合反应的表观活化能为22.1kJ·mol-1.     

Polymerization Mechanism of Vinyl Chloride with Trialkylaluminum-Lewis Base Catalyst and Thermal Stability of Poly(vinyl Chloride)

The mechanism of vinyl chloride polymerization by the tri-ethylaluminum-Lewis base-carbon tetrachloride catalyst system and the thermal stability of the resulting polymer were investigated. When the Lewis base is multidentate, the resultant complex with triethylaluminum shows significantly high catalytic activity for radical polymerization of vinyl chloride in the presence of carbon tetrachloride to give a white powder with high molecular weight. Carbon tetrachloride accelerates the rate of polymerization and participates in an initiating process rather than in a propagating step. The thermal stability of the polymer prepared with this catalyst system is much superior to that of commercial polyvinyl chloride), although the numbers of the double bonds in a chain end and of the head-to-head linkage are similar in both samples, suggesting that the thermally unstable structures of the former react with triethylaluminum to give the thermally stable structure on the polymerization process.     

Polymerization of vinyl monomers initiated by KO2–charge transfer agent systems. II

Vinyl monomers having electron acceptor groups such as nitroethylene, acrylonitrile, and acrolein were polymerized by KO₂–charge transfer agent initiator systems in dimethylsulfoxide (DMSO) at 25°C. The new initiator systems were found to be stable for almost 1 month under nitrogen atmosphere. The initial rate of polymerization was so fast that both conversion and molecular weight of the polymers obtained were high. Especially their molecular weight distribution was observed to be very narrow by means of gel permeation chromatography (GPC). The anion radicals generated by one electron transfer from potassium superoxide (KO₂) to charge transfer agents such as naphthalene, benzoquinone, azobenzene, etc., were suitable as initiator for the anionic polymerization of electron acceptor monomers. Study on block copolymerization of nitroethylene with acrylonitrile or acrolein was also attempted.     

Tetramethylguanidino‐tris(2‐aminoethyl)amine: A novel ligand for copper‐based atom transfer radical polymerization

With CuBr/tetramethylguanidino‐tris(2‐aminoethyl)amine (TMG₃‐TREN) as the catalyst, the atom transfer radical polymerization (ATRP) of methyl methacrylate, n‐butyl acrylate, styrene, and acrylonitrile was conducted. The catalyst concentration of 0.5 equiv with respect to the initiator was enough to prepare well‐defined poly(methyl methacrylate) in bulk from methyl methacrylate monomer. For ATRP of n‐butyl acrylate, the catalyst behaved in a manner similar to that reported for CuBr/tris[2‐(dimethylamino)ethyl]amine. A minimum of 0.05 equiv of the catalyst with respect to the initiator was required to synthesize the homopolymer of the desired molecular weight and low polydispersity at the ambient temperature. In the case of styrene, ATRP with this catalyst occurred only when a 1:1 catalyst/initiator ratio was used in the presence of Cu(0) in ethylene carbonate. The polymerization of acrylonitrile with CuBr/TMG₃‐TREN was conducted successfully with a catalyst concentration of 50% with respect to the initiator in ethylene carbonate. End‐group analysis for the determination of the high degree of functionality of the homopolymers synthesized by the new catalyst was determined by NMR spectroscopy. The isotactic parameter calculated for each system indicated that the homopolymers were predominantly syndiotactic, signifying that the tacticity remained the same, as already reported for ATRP. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5906–5922, 2005     

Poly(alkylene oxide) ionomers. VII. Use of triethylaluminum/water/acetylacetone (1.0:0.5:1.0) for the polymerization of oxiranes

Polymerization studies of oxiranes were conducted using a modified aluminumalkyl initiator, derived from the low-temperature reaction by chelating agents (5°C) and hydrolysis products of triethylaluminum. The stoichiometric reaction product of acetylacetone and triethylaluminum, after partial hydrolysis with water, gave a homogeneous initiator that polymerized the oxides of ethylene, propylene, 1-butene, 1-hexene, 3-chloro-1-propene, and 4,4,4-trichloro-1-butene to the corresponding high molecular weight poly(alkylene oxides). The initiator, similar in nominal composition to the classical trialkylaluminum/water/acetylacetone (1.0/0.5/1.0) initiator developed by Vandenberg, retained a high level of activity, when properly stored, for nearly 4 weeks. The composition was inactive when the sequence of chelation and hydrolysis was reversed. Inclusion of a proton-trapping agent in polymerization experiments of propylene oxide provided evidence that protons do not play a role in the initiation of oxirane polymerizations with modified organoaluminum oxides. Characterization of the various alkylene oxide polymers was carried out by spectroscopic, solution, and thermal techniques.     

Polymerization of acrylonitrile with VCl4–Al(C2H5)3 catalyst system in presence of acetonitrile

The polymerization of acrylonitrile with the homogeneous catalyst system of VCl₄–AlEt₃ in acetonitrile at 40°C has been investigated. The rate of polymerization is found to be first-order with respect to monomer and inversely proportional to the catalyst concentration. The overall activation energy for this catalyst system is 10.97 kcal/mole. The inverse proportionality of rate of polymerization with the catalyst concentration is attributed to the permanent complex formation between the catalyst complex and acrylonitrile, and a reaction scheme is proposed.     

Copper‐mediated initiators for continuous activator regeneration atom transfer radical polymerization of acrylonitrile

Initiators for continuous activator regeneration atom transfer radical polymerization technique was first accessed to acrylonitrile by using CuBr₂/2,2′‐bipyridine as the catalyst, ethyl 2‐bromoisobutyrate as the halogen initiator, and azobis(isobutyronitrile) as the free radical initiator. The key to success is ascribed to the facile achievement of the rapid equilibrium between active species and dormant species. Effects of ligand, catalyst concentration, free radical initiator concentration, and reaction temperature on the polymerization reaction and molecular weight (MW) as well as polydispersity index (PDI) were investigated in detail. The polymerization proceeded in a controlled/living fashion even though the concentration of copper catalyst decreased to 50 ppm, which is evident in pseudo first‐order kinetics of polymerization, linear increase of molecular weight, low PDI, and high chain‐end functionality of the generated polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Atom transfer radical polymerization of 2-methoxy ethyl acrylate and its block copolymerization with acrylonitrile

2-Methoxy ethyl acrylate (MEA), a functional monomer was homopolymerized using atom transfer radical polymerization (ATRP) technique with methyl 2-bromopropionate (MBP) as initiator and CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst system; polymerization was conducted in bulk at 60 °C and livingness was established by chain extension reaction. The kinetics as well as molecular weight distribution data indicated towards the controlled nature of polymerization. The initiator efficiency and the effect of initiator concentration on the rate of polymerization were investigated. The polymerization remained well-controlled even at low catalyst concentration of 10% relative to initiator. The influence of different solvents, viz. ethylene carbonate and toluene on the polymerization was investigated. End-group analysis for the determination of high degree of functionality of PMEA was determined with the help of ¹³C{¹H} NMR spectra. Chain extension experiment was conducted with PMEA macroinitiator for ATRP of acrylonitrile (AN) in ethylene carbonate at 70 °C using CuCl/bpy as catalyst system. The composition of individual blocks in PMEA-b-PAN copolymers was determined using ¹H NMR spectra.     

芳香族重氮盐氧化还原引发体系的研究——Ⅳ.利用4,4′-联苯双重氮硼氟酸盐进行嵌段共聚

提供了一种利用芳族双重氮盐进行嵌段共聚的新方法。研究了利用4,4′-联苯双重氮硼氟酸盐与亚铁盐引发丙烯腈低温沉淀聚合,使聚合物末端带上重氮基与包藏自由基,然后与甲基丙烯酸或丙烯酰胺进行嵌段共聚,所得嵌段共聚物为BAB型。研究了4,4′-联苯双重氮硼氟酸盐与亚铁盐引发丙烯酰胺水溶液聚合,使聚合物末端带有重氮基,再与丙烯腈或丙烯酸甲酯嵌段共聚。     

Polymerization of styrene with chromium acetylacetonate and triethylaluminum and diethylaluminum bromide

Kinetics of the polymerization of styrene in the presence of benzene at 30°C., with chromium acetylacetonate in combination with triethylaluminum and also in combination with diethylaluminum bromide as catalyst, have been studied. Chromium acetylacetonate forms a homogeneous system with triethylaluminum, and chromium acetylacetonate with diethylaluminum bromide behaves as a heterogeneous system. This homogeneous catalyst system, though reported inactive in the polymerization of α-olefins, has been found effective with styrene. Depending on the homogeneity and heterogeneity of the system, the rate of polymerization is proportional to half order and first order of catalyst concentration. A probable reason for the effect of homogeneity on the order of reaction has been discussed. A study of the effect of diethylzinc as a chain-transfer agent has helped to confirm the mechanism of polymerization.     

Anionic heterogeneous polymerization of methacrylonitrile by n-butyllithium

The anionic heterogeneous polymerization of methacrylonitrile by butyllithium in petroleum ether was investigated. The polymerization was of the “living” type, as seen from the linear dependence of the molecular weights on [MAN]/[BuLi]. This behavior was further supported by block polymerization experiments in which the monomer was added in two portions and the molecular weights obtained were directly proportional to the total monomer concentration. The initiator efficiency was low, and initiator consumption was only about 2%. This fact, together with the results of the block polymerizations showed that there was preferential addition of monomer to the growing chain ends rather than to the initiator. The molecular weights were independent of the rate of monomer addition. This as well as the “living” behavior of the polymerization of methacrylonitrile on a wide range of monomer and catalyst concentrations and the absence of chain transfer to monomer was essentially different from that of the similar heterogeneous polymerization of acrylonitrile by butyllithium previously investigated. This is due to the absence of an α-acidic hydrogen in methacrylonitrile.     

基团转移聚合法合成A-B型嵌段共聚物

用基团转移聚合法(GTP)合成嵌段共聚物是近年来国际上高分子研究的热门之一.在室温下制备嵌段共聚物是GTP的一大特点.本文利用三类不同GTP单体的活性差别^[1,2],控制适当的加料顺序及聚合条件,首次用GTP法合成含丙烯腈嵌段的A-B型共聚物并进行表征.     

Vinyl Polymerization. 274. Polymerization of Acrylonitrile Initiated by the System Tetramethyl Tetrazene and Co(II) Chloride

Abstract

The binary system of tetramethyl tetrazene (TMT) and Co(II) chloride was used as initiator of acrylonitrile (AN) in dimethylformamide. The initial rate of polymerization (Rp) was found to be expressed by Rp = k[TMT]^0.62[Co(II) chloride]^0.57 [AN]^2.00

The polymerization was confirmed to proceed via a radical mechanism. The over-all activation energy for the polymerization was estimated as 15.1 kcal/mole. On the basis of these results and the product analysis of the reaction between the catalyst components in the absence of monomer, the initiation mechanism of the polymerization is discussed.     

Kinetics of copolymerization—I. Kinetic investigation of the polymerization of acrylonitrile in homogeneous phase

A detailed study was made of the kinetics of initiated homopolymerization of acrylonitrile in dimethylformamide and dimethylsulphoxide at 40–60°. The rate of polymerization was found to be proportional to the (initiator concentration)^1/2. The rate of initiation of polymerization was determined by the inhibition method, using three stable free radicals. Trends in the average rate of polymerization were also studied for various initial monomer and solvent concentrations. The overall rate constant (K) was strongly dependent on monomer concentration decreasing with decrease of monomer concentration. It has been shown that the hot radical theory describes accurately, without physical contradiction, the solvent dependence of rate constants of polymerization systems.     

Acidic peroxo salts. A new class of initiators for vinyl polymerization. I. Kinetics of polymerization of acrylonitrile initiated by potassium monopersulfate catalyzed by Ag(I)

The kinetics of polymerization of acrylonitrile initiated by KHSO₅ and catalyzed by Ag(I) have been investigated in an aqueous medium over the temperature range of 35–50°C. The rates of polymerization R_p have been calculated and studied with respect to monomer and initiator. The catalytic activity of various metal ions on the initiator has been determined from a comparison of R_p values. The effects of monomer, catalyst, neutral salts, various amines, and inhibitor (hydroquinone) on the initial rate as well as maximum conversion have been studied. From the kinetics results a suitable reaction scheme has been proposed.     

Vinyl polymerization initiated by peroxydiphosphate. V. Polymerization of acrylonitrile initiated by peroxydiphosphate-cyclohexanol redox system in the presence of silver ion

The polymerization of acrylonitrile was carried out using peroxydiphosphate-cyclohexanol redox system in the presence of silver ion. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The plot of R_p vs [Ag⁺]^1/2 was linear, indicating 0.5 order with respect to [Ag⁺]. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 7.60 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been pictured.     

Crown Ether As The Phase-Transfer Catalyst for Free Radical Polymerization of Hydrophobic Vinyl Monomers

Various crown ethers were used as phase-transfer catalysts for free radical polymerizations of some water-insoluble vinyl monomers such as acrylonitrile, methylmethacrylate and styrene with persulfate as initiator. The catalytic abilities of these crown ethers for free radical polymerization of acrylonitrile with S₂O₈^2?ion as an initiator were in the order: 18-crown-6 > 15-crown-4 > 12-crown-4 > benzo-15-crown-5 > dibenzo-18-crown-6. Among various persulfates such as Na₂S₂O₈ K₂S₂O₈ and (NH₄)₂S₂O₈, ammonium persulfate was the optimum initiator for the polymerization of acrylonitrile catalyzed by 18-crown-6 or 15-crown-5. Among the organic solvents used, chloroform seems to be the best solvent for the catalytic polymerization of acrylonitrile. An apparent activation energy of 72.9 kJ mol^?1 was observed for the polymerization of acrylonitrile. The catalytic reaction rates of free radical polymerization for these hydrophobic vinyl monomers were in the order: acrylonitrile > methylmethacrylate > styrene > isoprene. Effects of concentrations of crown ether, initiator, and nitrogen on the polymerization of these vinyl monomers were investigated.