Metal-containing initiator systems. VI. Polymerization of butadiene with metal–organic halide systems

The polymerization of butadiene with binary initiator systems consisting of some activated metals and organic halides was investigated at 60°C. From the results obtained, it was found that systems of reduced nickel and methyltrichlorosilane or dimethyldichlorosilane were most effective for the polymerization, and those of reduced nickel and carbon tetrachloride, benzyl chloride, benzyl bromide and benzoyl chloride, showed moderate activity. The polybutadienes obtained with these systems were observed to contain product of more than 80% cis-1,4 microstructure. From detailed studies on the reduced nickel–methyltrichlorosilane system, these polymerization mechanisms were explained by the hypothesis that the initiation occurred through the reaction of the dissociated transition state complex with the monomer or with a trace amount of water, and then the propagation proceeded via a coordinated cationic mechanism. These systems did not show a good activity for the cis-1,4 polymerization of isoprene.     

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.     

The initiation of vinyl polymerization by tetrakis (trialkyl-phosphite) nickel (o) derivatives

The study of the polymerization of vinyl monomers initiated by zero-valent nickel phosphite derivatives in the presence of organic halides has been extended to tetrakis (triethylphosphite) nickel (o) and tetrakis (tri 2-chloroethylphosphite) nickel (o). A kinetic study with methyl methacrylate and carbon tetrachloride shows that the polymerization proceeds by a free radical process and that the mechanism of initiation resembles that previously reported for the corresponding triphenylphosphite and carbonyl derivatives. The primary process which becomes rate determining at sufficiently high carbon tetrachloride concentration is the nonreversible S_N1 scission of an alkylphosphite ligand. These alkylphosphite initiators are considerably more active than the corresponding carbonyl derivatives, but are less active than the corresponding triphenyl-phosphite derivative. The difference in activities between the aryl and alkylphosphite derivatives has been accounted for by differences in steric over-crowding of these molecules.     

Polymerization of vinyl monomer with carbon disulfide–alkali metal complex

The reaction of carbon disulfide with one or two equivalents of alkali metal (potassium- or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono- and dialkali metal with carbon disulfide induced the polymerization of N-phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was ?1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units.     

Kinetic studies of nonaqueous polymerization of methyl methacrylate initiated by ferric laurate–n-hexyl amine system

The polymerization of methyl methacrylate was studied in carbon tetrachloride medium with ferric laurate, a metal soap, in combination with n-hexyl amine as the initiator system at 60°C. The rate of polymerization was found to be linear with the monomer concentration and proportional to the square root of both ferric ion and amine concentration. A reaction scheme involving initial complex formation between ferric ion and amine and subsequent reaction of the complex with the solvent molecule to produce free radicals responsible for initiation of polymerization has been postulated to account for the observed results.     

Vinyl Polymerization. 254.∗ Polymerization of Methyl Methacrylate by the System Cellulose-Water-Carbon Tetrachloride

Radical polymerization of methyl methacrylate initiated by the system cellulose-water-carbon tetrachloride was kinetically studied. Results obtained are: 1) The amounts of water, carbon tetrachloride, and cellulose affected the conversion. Michaelis-Menten's equation was applied to the relationship between the rate of polymerization and the amount of MMA. 2) Other methacrylates and acrylates were also polymerized by this system. 3) When methanol or ethanol was used instead of water, some weak polymerization activity was observed. 4) Initiating ability depended on the kind of cellulose used. 5) The activity of cellulose was not changed by washing with boiling water or by solvent extraction. 6) Polymerization was inhibited by the presence of air. 7) Heating in the presence of water and carbon tetrachloride markedly decreased the activity of the cellulose.     

Polymerization initiated by an electron donor–acceptor complex. Part IV. Kinetic study of polymerization of methyl methacrylate initiated by the charge-transfer complex consisting of poly-2-vinylpyridine and liquid sulfur dioxide

A kinetic study has been made of the polymerization of methyl methacrylate (MMA) initiated by a charge-transfer complex of poly-2-vinylpyridine (electron donor) and liquid sulfur dioxide (acceptor) in the presence of carbon tetrachloride. It is concluded that the polymerization proceeds through free-radical intermediates, as with the pyridine-liquid sulfur dioxide complex system. The association constants K of acceptor and polymer electron donors which range widely in their molecular weight were determined spectrophotometrically, and it has been found that both K and overall rate of polymerization R_p of MMA decrease with increasing molecular weight of polymer donor; contrary to this, molecular weight of PMMA formed increases with increasing molecular weight of the polymer donor. Other kinetic behaviors was essentially the same as in the pyridine–liquid sulfur dioxide system, i.e., R_p is proportional to the square root of the concentration of the complex and to the 3/2-order of the monomer concentration; R_p is clearly sensitive to the carbon tetrachloride concentration at low concentration of carbon tetrachloride, but for a higher concentration it is practically independent of the carbon tetrachloride concentration. It has been deduced from a kinetic mechanism for the initiation that a primary radical may be produced from the reduction of carbon tetrachloride by an associated complex consisting of liquid sulfur dioxide–polymer donor and the monomer.     

Polymerization of coordinated monomers. I. Stereoregulation in the free-radical polymerization of methyl methacrylate-zinc chloride or methyl methacrylate–stannic chloride complexes

Stereoregulation in free-radical polymerization was studied for the polymerization of the 2:1 or 1:1 complex of methyl methacrylate with ZnCl₂ or SnCl₄. The complexes were polymerized with the use of a free-radical initiator or γ-ray irradiation either in the liquid or solid state at various temperatures ranging from ?196 to 110°C, and the tacticities of the resulting polymers were determined by NMR spectroscopy. The polymers had different and characteristic values of tacticities depending upon the complex species, i.e., the kind of metal chloride and the stoichiometry. The tacticities were found to be independent of the polymerization temperature in both the liquid and solid states, in contrast with the fact that tacticities of the polymer from pure monomer changed markedly with the temperature. A temperature dependence appeared in the polymerization system, which contained more monomer than that corresponding to the 2:1 complex. The effect of the viscosity or the solid phase on the stereoregulation was examined in comparison with the polymerization of a mixture of methyl methacrylate and liquid paraffin. Two possible explanations regarding the stereoregulation mechanism are offered in relation to the structures of the complexes.     

Polymerization of methyl methacrylate initiated by tri-n-butylborane–organic halide systems

The polymerization of methyl methacrylate (MMA) initiated by tri-n-butylborane (TBB) was studied in the presence of various organic halides (R′X). It was found that R′X accelerated the polymerization of MMA. Aliphatic halides were more effective than aromatic halides. Cocatalytic effects of butyl halides decreased in the order: n -BuI > n -BuBr > n -BuCl; n -BuBr ? sec-BuBr > i-BuBr > tert-BuBr. In the polymerization of MMA by TBB- n -BuI, the initial rate of polymerization was found to be proportional to the concentration of MMA and to the square root of the concentration of TBB-n-BuI. The apparent activation energy was 5.3 kcal/mole. From this and other results, it was assumed that the polymerization of MMA by this initiator system proceeds by a radical mechanism via a weak complex between TBB and R′X; alkyl radicals are formed by the interaction of R′X with TBB. The TBB–R′X system can initiate the polymerization of MMA and AN, but is ineffective in the polymerization of styrene.     

Effect of Stabilizer Concentration,Pressure and Temperature on Polymerization Rate and Molecular Weight Development in RAFT Polymerization of MMA in scCO2

Summary: An experimental study on the effect of stabilizer concentration, pressure (100 to 500 bar), and temperature (65 to 85 °C) on polymerization rate and molecular weight development in the reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) in supercritical carbon dioxide (scCO₂) is presented. AIBN was used as initiator, S-Thiobenzoyl thioglycolic acid as RAFT agent, and Krytox® 257 FSL as stabilizer. It was observed that the polymerization proceeded in a controlled manner. High conversions can be reached in reasonable times. Fairly low polydispersities (around 1.2) are possible if either pressure or temperature are increased, but better results are obtained if the polymerization proceeds at the upper temperature value of 85 °C.     

Effect of initiators on grafting in the initial stage of the emulsion polymerization of methyl methacrylate using poly(vinyl alcohol) as a protective colloid

 To make clear the reason of unsuitability of poly(vinyl alcohol) (PVA) protective colloid for the emulsion polymerization of conjugated monomers, a model experiment of emulsion polymerization of methyl methacrylate (MMA) was carried out with ammonium persulfate (APS) or azobis(isobutyronitrile) (AIBN) initiators, where a small amount of MMA (1/100th of the concentration compared with ordinary emulsion polymerization) was employed. This corresponds to the initial stage of the emulsion polymerization. Grafting of MMA onto PVA took place remarkably irrespective of the kind of the initiators. Formation of homo-poly(MMA) was observed to a small extent. The formation of new emulsion particles smaller than 100 nm continued to increase to almost the end of the polymerization. PVA molecules in the grafted polymer are supposed to act as stabilizers of newly formed particles. From kinetic treatment using the experimental data, the important issues were derived as follows. Firstly, the sulfate anion radical from APS is much more reactive than the isobutyronitrile radical from AIBN in terms of hydrogen abstraction from PVA. Secondly, high grafting ability of the latter initiator system, notwithstanding the much lower reactivity in the hydrogen abstraction compared with the APS system, is attributed to the relative reactivity of the primary radicals, i.e., hydrogen abstraction reaction from PVA to initiation reaction with MMA. The much slower rate of addition of the isobutyronitrile radical to the monomer compared with that of hydrogen abstraction from PVA facilitates the grafting, although the rate constant of hydrogen abstraction is far smaller than that with the sulfate anion radical by 10⁻⁴ times. Received: 26 April 2001 Accepted: 6 September 2001     

Atom transfer radical addition (ATRA) catalyzed by copper complexes with tris[2-(dimethylamino)ethyl]amine (Me6TREN) ligand in the presence of free-radical diazo initiator AIBN

In this article, we focus on the evaluation of tris[2-(dimethylamino)ethyl]amine (Me(6)TREN) ligand in copper catalyzed ATRA in the presence of free-radical diazo initiator AIBN (2,2'-azobis(2-methylpropionitrile)). The addition of carbon tetrachloride to 1-hexene, 1-octene and cis-cyclooctene proceeded efficiently to yield 89, 85 and 85% of monoadduct, respectively, using the catalyst to alkene ratio of 1 : 2500. For alkenes that readily undergo free radical polymerization, such as methyl acrylate, catalyst loadings as high as 0.4 mol-% were required. Furthermore, modest yields of the monoadduct were obtained with less active alkyl halides (chloroform and bromoform) using 250 : 1 and 500 : 1 ratios of alkene to copper(II). Interestingly, the addition of carbon tetrachloride to cis-cyclooctene produced only 1-chloro-4-(trichloromethyl)-cyclooctene, while carbon tetrabromide yielded 1,2 and 1,4-regioisomers in 75 : 25 ratio. The activity of [Cu(II)(Me(6)TREN)X][X] (X = Br(-) and Cl(-)) complexes in ATRA in the presence of AIBN was additionally probed by adding excess free ligand, source of halide anions and triphenylphosphine. The results indicated that disproportionation is a likely cause for lower activity of Me(6)TREN as compared to TPMA (tris(2-pyridylmethyl)amine).     

Metal-Containing Initiator Systems. XXIX. Selective Initiation of Vinyl Polymerizations with Cobaltocene

The polymerizations of acrylonitrile (AN), acrolein (AL), butadiene (BD), and isobutyl vinyl ether (EBVE) with cobaltocene were investigated. It was found that both AN and AL could polymerize in dimethyl sulfoxide through a coordination mechanism, but AN and BD polymerized by a radical mechanism in the presence of some organic halides, such as carbon tetrachloride, benzyl bromide, and allyl bromide. The initiator system of cobaltocene and organic halide also induced cationic polymerization of IBVE. On the basis of the results obtained, a mechanism for the selective initiation of polymerization is proposed and discussed.     

Free-radical polymerization of methyl methacrylate in the presence of a ferrocenyl-containing iron(II) clathrochelate complex and initiators of various natures

Benzoyl peroxide-, lauryl peroxide-, and AIBN-initiated free-radical polymerization of methyl methacrylate has been studied in bulk and solution in the presence of macrobicyclic iron(II) bis(ferrocenyl borate) tris(nioximate). It has been found that the ferrocenyl-containing iron(II) clathrochelate forms efficient initiating systems with peroxides, whereas, in the case of AIBN, its presence has no effect on the kinetic parameters of the process and the properties of the resulting polymer. The use of clathrochelate complex-peroxide initiator systems accelerates the polymerization of methyl methacrylate and decreases the molecular mass of the polymer. The kinetic parameters of the process have been determined.     

Polymerization of methyl methacrylate with cupric laurate-N,N-dimethyl formamide as initiator system

The polymerization of methyl methacrylate with cupric laurate in combination with N,N-dimethyl formamide as initiator was studied in carbon tetrachloride medium at 60°C. The rate of polymerization was found to be proportional to the 3/2th power of the monomer concentrations and to the square root of both cupric laurate and DMF concentrations. Spectroscopic investigations indicated a ternary complex formation involving cupric ion, methyl methacrylate, and DMF. A reaction scheme is suggested on the basis of these results and various kinetic constants have been evaluated.     

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。     

STUDY ON THE POLYMERIZATION KINETICS AND STABILITY OF P(UA)/MMA MICROEMULSION*

 Urethane acrylate anionomer (APUA) as a kind of new type polymerizable emulsifier was synthesized using 2,4-toluene diisocyanate (TDI), polypropylene glycol (PPG), 2-hydroxyethyl methacrylate (HEMA) and dimethylolpropionic acid (DMPA). The critical micelle concentration (CMC) of APUA was measured by the methods of conductance and surface tension. The comparative studies between polymerizable emulsifier AUPA and conventional emulsifier sodium dodecyl sulfate (SDS) were carried out in the emulsion polymerization of methyl methacrylate (MMA). Polymerization kinetics,stability, size and morphology of the latex particles were investigated. It was found that in APUA both water soluble initiator potassium persulfate (KPS) and oil soluble initiator 2,2'-azobisisobutyronitrile (AIBN) can start the reaction of MMA, and the polymerization rate and yield were very high. On using AIBN as an initiator, the conversion-time behavior of MMA with APUA as emulsifier was different to that of SDS as emulsifier, signifying a different nucleation mechanism of the polymer latex particle. The average size of the two kinds of particles is about 50 nm. The particle size decreases with increasing emulsifier concentration. On using KPS as the initiator, APUA as emulsifier, cross-linking hydrogel of PMMA would be formed, but SDS was used as emulsifier and the hydrogel of PMMA was not present.     

Functional polymers for colloidal applications. V. Novel behavior of polymeric emulsifiers in emulsion polymerization

The polymeric emulsifier poly(dodecyl acrylate-co-acrylic acid) [i.e., the sodium salt (PDA)] and monomeric emulsifier sodium dodecyl glutarate (SDG) have been synthesized. PDA and SDG are used as emulsifiers in the emulsion polymerization of styrene with both the water-soluble initiator potassium persulfate (K₂S₂O₈) and the oil-soluble initiator 2,2′-azobisisobutyronitrile (AIBN). The PDA/K₂S₂O₈ system showed a bimodel distribution of particle sizes (2 and 0.05 μm). A bimodel particle distribution was also found for the PDA/AIBN system, but the distribution for the large particles was wide (0.1–10 and 0.07 μm). The SDG/K₂S₂O₈ system displayed only one kind of particle size (0.05 μm), but the SDG/AIBN system also showed a bimodel distribution of particle sizes (0.05 and 5 μm). These bimodel distribution results for the PDA/K₂S₂O₈, PDA/AIBN, and SDG/AIBN systems indicate that the polymerization sites are both in oil droplets and in micelles (polymer aggregates). This mechanism is interpreted in terms of the formation of polymer aggregates, which is supported by the results of pyrene solubilization, pyrene fluorescence, surface tension, and pyrene excimer experiments. © 1993 John Wiley & Sons, Inc.     

Vinyl Polymerization. 287. Polymerization of Methyl Methacrylate Initiated by the Polyacrylonitrile-Water-Cupric Ion System

Abstract

Methyl methacrylate was found to be polymerized by the system polyacrylonitrile-water-cupric ion without any added initiator. Addition of carbon tetrachloride to this system greatly increased the polymerization rate. Acrylonitrile and styrene did not polymerize in this system. The kinetic behavior of polymerization was the same as the system consisting'of cellulose or nylon instead of polyacrylonitrile. When the flaky polyacrylo-nitrile was swelled or dissolved by the solvent DMF, the conversion and the degree of polymerization of the poly-methyl methacrylate formed decreased markedly. Commercial acrylic fiber also initiated polymerization but the activity was lower than with flaky polyacrylonitrile, even after steam treatment, because of the poor permeability of monomer into the fiber.     

Effect of triphenyl phosphite on the radical polymerization of styrene and methyl methacrylate

The effects of triphenyl phosphite (TPP) on the radical polymerization of styrene (St) and methyl methacrylate (MMA) initiated with α,α,-azobisisobutyronitrile (AIBN) was investigated at 50°C. The rate of polymerization of St and MMA at a constant concentration of TPP was found to be proportional to the monomer concentration and the square root of the initiator concentration. The rate of polymerization and the degree of polymerization of both St and MMA increased with increasing TPP concentration. The accelerating effect was shown to be due to the decrease of the termination rate constant k_t with an increase in the viscosity of the polymerization systems. The chain transfer constant C_tr of TPP in St and MMA systems was determined from the degree of polymerization system. The C_tr of TPP was almost zero in the St system and 6.5 × 10^?5 in the MMA system.