Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. VIII. Polymerization of styrene and methyl methacrylate adsorbed on aerosil

Aerosil is silica having a purity which is very high compared with that of silica gel and having, unlike silica gel, no micropores. To investigate the effects of impurities and micropores on the radiation-induced polymerization of styrene and methyl methacrylate adsorbed on silica gel, the radiation-induced polymerization of styrene and methyl methacrylate adsorbed on Aerosil was carried out. The results of both the styrene–Aerosil 300 system and the methyl methacrylate–Aerosil 300 system were similar to those of the styrene–silica gel and methyl methacrylate–silica gel systems, respectively. This suggests that in the radiation-induced polymerization of both styrene–silica gel and methyl methacrylate–silica gel systems the impurity and the presence of micropores have almost no effects on the reaction mechanism. The effect of aluminum as an impurity was investigated on the styrene–Aerosil MOX 170 system. It was found that aluminum accelerated the cationic polymerization.     

Modeling of elementary reactions and kinetics of radical‐initiated methyl methacrylate polymerization in the presence of ferrocene

On the basis of quantum chemical modeling, a kinetic scheme of methyl methacrylate polymerization initiated by benzoyl peroxide in the presence of ferrocene was proposed. The process runs by mechanism, which includes the reactions of free radical polymerization, and the reactions leading to formation and operability of two type coordination active sites that are capable of converting into each other. On the basis of the proposed scheme, a kinetic model was developed. This model quantitatively described the following: the experimentally determined time dependences of the methyl methacrylate conversion, the conversion dependencies of the number‐average and weight‐average molar masses of poly(methyl methacrylate), the stereoregularity values of poly(methyl methacrylate), and the time dependencies of the methyl methacrylate conversion upon its polymerization on poly(methyl methacrylate) macroinitiators obtained in radical‐initiated polymerization in the presence of ferrocene. As a result of solving the inverse kinetic problem, the parameters of temperature dependences of the reaction rate coefficients of the proposed kinetic scheme were found.     

Features of the physicomechanical behavior of poly(methyl methacrylate) synthesized by frontal polymerization

The physicomechanical properties of poly(methyl methacrylate) obtained by frontal polymerization were studied. The possibility of synthesizing materials with a higher glass-transition temperature by passing from bulk polymerization to frontal polymerization was shown. Deformation mode spectra of poly(methyl methacrylate) synthesized by frontal polymerization were plotted for the first time.     

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

A kinetic investigation of the alternating copolymerization of butadiene and methyl methacrylate with the use of a system of ethylaluminum dichloride and vanadyl chloride as a catalyst was undertaken. The relation between the polymer yield and the molar fraction of methyl methacrylate in the feed was examined by continuous variation of butadiene and methyl methacrylate, the concentrations of total monomer, ethylaluminum dichloride, and vanadyl chloride being kept constant. This continuous variation method revealed that the polymer yield attains its maximum value with a monomer feed containing less than the 0.5 molar fraction of methyl methacrylate. This value of the molar fraction of methyl methacrylate affording the maximum polymer yield decreased on increasing the total monomer concentration but was not changed on varying the concentration of ethylaluminum dichloride. The number of active species estimated from the relation between yield and molecular weight of the polymer was almost constant, regardless of the molar fraction of methyl methacrylate in the feed. Consequently, it can be said that the maximum polymer yield depends mainly on the propagation reaction, not on the initiation reaction or the termination reaction. Three types of the mechanism have been discussed for this alternating copolymerization: polymerization via alternating addition of butadiene and methyl methacrylate complexed with ethylaluminum dichloride by the Lewis-Mayo scheme; polymerization via the ternary intermediate of butadiene, methyl methacrylate, and ethylaluminum dichloride; polymerization via the complex formation of butadiene and methyl methacrylate complexed with ethylaluminum dichloride occurring only at the growing polymer radical. From the kinetic results obtained, it was shown that the first and third schemes are excluded, and polymerization by way of the ternary intermediate is compatible with the data.     

Some Studies on the Plasma-Initiated Polymerization of Methyl Methacrylate in the Liquid State

Previous results obtained for the free radical polymerization of methyl methacrylate were used to predict the mechanism of plasmainitiated polymerization of this monomer in the liquid state. The data obtained by use of high resolution NMR spectra strongly predict a free radical mechanism for the plasma-initiated polymerization of methyl methacrylate.     

<Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide-initiated radical polymerization of vinyl monomers

The initiating ability of N-hydroxyphthalimide in polymerization of methyl methacrylate and acrylonitrile was examined. For the polymerization of methyl methacrylate, the initial polymerization rates and activation energies were determined, and the dependences of the polymerization rates on the initiator and monomer concentrations were evaluated. An initiation mechanism was suggested.     

离子液体对甲基丙烯醛氧化酯化反应的影响

异丁烯氧化制备甲基丙烯酸甲酯(MMA)是一条极具优势、清洁高效的工艺技术路线.但甲基丙烯酸甲酯极易聚合^[1],故异丁烯三步法及传统的丙酮氰醇法均在酯化过程中加入对苯二酚、对羟基苯甲醚、2,4-甲基-6-叔丁基苯酚等有机物作为阻聚剂^[2].而甲基丙烯醛直接氧化酯化为MMA时,碱性和加热的反应条件使MMA更易聚合^[3].因而防止MMA在反应过程中的聚合成为工艺技术的关键问题.本文在甲基丙烯醛一步氧化酯化生成MMA的反应体系中添加离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bm im]PF₆),结果表明,该离子液体既能提高MMA的选择性还有效防止MMA的聚合.     

Synthesis of graft copolyimides via controlled radical polymerization of methacrylates with a polyimide macroinitiator

The atom-transfer radical polymerization of methyl methacrylate and tert-butyl methacrylate with a polyimide multicenter macroinitiator in the presence of a CuCl-2,2′-bipyridine catalytic system is investigated. The kinetic features of the process, the molecular-weight characteristics of the formed side chains, and the post-polymerization of methyl methacrylate with graft polyimides containing polymethacrylate side chains are studied. The conditions of controlled polymerization yielding graft copolyimides with narrowly dispersed living poly(methyl methacrylate) or poly(tert-butyl methacrylate) side chains of variable lengths are determined.     

Branched poly(methyl methacrylates) modified by C60 fullerenes

The poly(methyl methacrylates) of branched structure with a covalently bonded fullerene were synthesized by three-dimensional radical polymerization of methyl methacrylate with triethylene glycol dimethacrylate or allyl methacrylate in toluene containing C₆₀. The kinetics of copolymerization of methyl methacrylate with multifunctional co-monomers in the absence of fullerene is compared with that in its presence. The physicochemical characteristics and thermal stability of the obtained copolymers are also compared. The electron spin resonance (ESR) method was applied to study the kinetics of accumulation of the fullerene radicals in the course of the (co)polymerization of methyl methacrylate.     

Effects of chlorophosphines on the radical polymerization of methyl methacrylate

The effect of chlorophosphines (phosphorus trichloride, dichlorophenylphosphine, chlorodiphenylphosphine) on the radical polymerization of methyl methacrylate was investigated in benzene solution. The polymerization was carried out at 50°C by the standard solution method, α,α′-azobisisobutyronitrile being used as an initiator. These chlorophosphines accelerated the polymerization of methyl methacrylate but did not affect the rate of decomposition of α,α′-azobisisobutyronitrile. Ultraviolet and infrared spectral data suggested that the acceleration effect was due to the complex formation of methyl methacrylate with each chlorophosphine. From the result of a copolymerization with styrene, it was found that the reactivity of methyl methacrylate monomer increased in the presence of dichlorophenylphosphine.     

聚羧酸铜/亚硫酸钠体系引发甲基丙烯酸甲酯聚合的研究

以杨梅型(聚丙烯接枝)聚羧酸铜/亚硫酸钠体系引发甲基丙烯酸甲酯水溶液聚合,测得表现聚合速率 R_p=1.2×10~(14)e~(-21,400/RT)[MMA]~(1.3)[Na_2SO_3]~(0.5)[P-Cu]~0 聚合按自由基机理进行。聚羧酸铜/亚硫酸钠/甲基丙烯酸甲酯之间通过“络合-氢转移”过程产生初级自由基。     

Polymerization of vinyl monomers in the water–1,4-dioxane system containing peroxide and water-soluble polymer

Water-solube polymer (PST) containing triethylenetetramine side chain was prepared by the amination of chloromethylated polystyrene with triethylenetetramine in 1,4-dioxane. The polymerization of vinyl monomers was carried out in the water–organic solvent system containing PST and a very small amount of peroxide. The polymerization of methyl methacrylate proceeded smoothly in the presence of both peroxide and PST. It was found that the polymerization was initiated with the radicals generated by the interaction between hydroperoxide and amino groups of PST. 1,4-Dioxane hydroperoxide showed a high activity for the polymerization of methyl methacrylate. The maximum rate of the polymerization was observed at 60°C and in an approximately neutral solution. The addition of suitable amount of Cu(II) accelerated the polymerization of methyl methacrylate. The selective polymerization of vinyl monomers was observed in this system.     

消除甲基丙烯酸酯类单体阴离子聚合副反应的几种主要方法

本文论述了甲基丙烯酸酯类单体阴离子聚合过程中主要副反应的机理，重点讨论了三类主要的化合物（金属烷氧基化合物，金属卤化物和冠醚类化合物）对于甲基丙烯酸酯类单体阴离子活性中心的稳定作用。     

Controlled radical polymerization of methacrylates of various structures in the presence of the AIBN-FeCl3-N,N-dimethylformamide catalytic system

The controlled radical polymerization of methyl methacrylate, 2-ethoxyethyl methacrylate, and tert-butyl methacrylate conducted via atom-transfer radical polymerization in the presence of the AIBN-FeCl₃· 6H₂O-N,N-dimethylformamide catalytic system is studied. For all the systems under study, the rate of reaction is first order with respect to the monomer concentration. The number-average molecular mass of the polymers linearly increases with conversion, and their polydispersity indexes are below 1.6. The rate of polymerization decreases in the following sequence: 2-ethoxyethyl methacrylate > methyl methacrylate > tert-butyl methacrylate. The presence of ω-terminal chlorine atoms in polymer macromolecules is confirmed by ¹H NMR spectroscopy and through the block copolymerization of methyl methacrylate with a poly(ethoxyethyl methacrylate)-based macroinitiator.     

Synthesis of Comblike Poly（methyl methacrylate） by Atom Transfer Radical Polymerization with Poly（ethyl 2-bromoacrylate） as Macroinitiator

Comblike poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical polymerization of ethyl 2-bromoacrylate. The obtained comblike polymers were characterized by GPC and ^1H NMR.     

Polymerization of methyl methacrylate with ceric ion-methanol redox system

The polymerization of methyl methacrylate initiated by Ce⁴⁺ methanol redox system was studied in aqueous solution of nitric acid at 15°C. The polymerization was initiated by primary radicals formed from Ce⁴⁺/alcohol complex. Poly(methyl methacrylate) chains containing the alcohol residue were obtained. Variations in the temperatuare and concentration of the components of the redox system allowed the control of the rate of polymerization and molecular weight of the polymer. The concentration of the hydroxyl end groups in the poly(methyl methacrylate) of low molecular weight was determined by titration and by spectrometric method.     

Radical polymerization of vinyl monomers initiated by a mono-captodatively substituted ethane

Homopolymerization of styrene and methyl methacrylate was carried out at 60–130°C in the presence of a mono-captodatively (cd) substituted ethane bearing nitrile and ethylsulfenyl substituents on the same carbon atom. It was found that the cd-ethane accelerated both styrene and methyl methacrylate polymerizations with no induction period, but the polymerization mode of methyl methacrylate was different from that of styrene. The polymerization rate of styrene was proportional to the 0.46th power of the cd-ethane concentration. However, the cd-ethane produced a reversible radical termination in the case of methyl methacrylate. The mechanism of both polymerizations is discussed in terms of the kinetic and ESR data. © 1996 John Wiley & Sons, Inc.     

Polymerization of methyl methacrylate by the binary system of the copper–amine complex type resin and carbon tetrachloride

The polymerization of vinyl monomers initiated by binary initiator systems composed of a copper–amine complex type resin and organic halides has been studied. These binary systems initiated the polymerization of various vinyl monomers. A kinetic study of the polymerization of methyl methacrylate initiated by the copper–amine complex resin–CCl₄ system was carried out, and it was found that the polymerization proceeds by way of a radical mechanism. This fact was also supported by the copolymerization of methyl methacrylate with styrene. The overall activation energy of the polymerization of methyl methacrylate was estimated as 8.4 kcal/mole. The activity of the initiator systems was greatly dependent upon the dissociation energy of carbon–halogen bonds in the organic halides. A possible initiation mechanism with the binary systems is proposed and discussed.     

N-乙烯基咔唑与卤代烃引发甲基丙烯酸甲酯聚合的研究

<正> N-乙烯基咔唑(NVC)具有大的共轭结构和中间有一个杂原子氮,而容易与其它试剂反应,形成自由基、阳离子和电荷转移络合物,故是一种活性较高的单体,1970年有人发现NVC与N-C_4H_9NCl_2一起可以引发甲基丙烯酸甲酯(MMA)聚合,此外,文献报道了电子给体如胺与CCl_4体系在二甲亚砜(DMSO)中引发MMA聚合,本文研究了NVC与几种卤代烃所组成的双组分体系对MMA的引发聚合反应;该体系的引发活性和组成与分子量及分子量分布的关系;并探讨了反应机理。     

Polymerization of Vinyl Monomers Using Oxidase Catalysts

Polymerization of vinyl monomers using oxidase as catalyst has been performed under argon in the presence of acetylacetone as a mediator and without the use of hydrogen peroxide. The polymerization of acrylamide was catalyzed by a laccase or sarcosine oxidase catalyst in distilled water and efficiently produced the polymer with high molecular weight. In the polymerization using the laccase catalyst, the effects of temperature, time, and amounts of enzyme and mediator have been systematically investigated. On the other hand, various other oxidases such as bilirubin, choline, and xanthine oxidases showed no or little activity for the vinyl polymerization. The laccase/acetylacetone catalyst induced the polymerization of methyl methacrylate and styrene in a mixture of water and tetrahydrofuran. Laccase alone also acted as a catalyst for the vinyl polymerization of acrylamide and methyl methacrylate without acetylacetone. In the polymerization of methyl methacrylate using lipoxidase as the catalyst in the presence of acetylacetone, the reaction occurred in air.