超临界二氧化碳中的高分子合成

近年来,超临界二氧化碳（sc-CO2）在聚合反应中的应用受到了越来越多的关注。本文主要综述了以sc-CO2为反应介质的自由基聚合、阳离子聚合、过渡金属催化聚合、热致开环聚合、溶胶-凝胶聚合以及氧化耦合聚合的研究概况。一系列研究结果表明sc-CO2是非常有前途的反应溶剂,在高分子合成领域将会有更加广阔的应用前景。     

超临界CO2中的高分子合成研究进展

本文介绍以超临界CO₂流体为介质的高分子合成的研究进展。说明可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯和苯乙烯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应。这显示出超临界CO₂是一种对环境无污染且价廉的替代溶剂。     

Cationic ring-opening transfer polymerization of spiro ortho esters initiated by carbon black

The ring-opening transfer polymerization of spiro ortho esters (SOE) initiated by carbon black was investigated. In the absence of carbon black, no polymerization occurred at all. In the presence of channel black containing carboxyl group, the ring-opening transfer polymerization of SOE was initiated at 50-70°C. to give polyether ester, namely alternating copolymer of epoxide and lactone. The rate of polymerization of 1,4,6-trioxaspiro[4.4]nonane and 1,4,6-trioxaspiro[4.5]decane was considerably small compared with that of 1,4,6-trioxaspiro[4.6]undecane. The activation energy of the polymerization of 2-chloromethyl-1,4,6-trioxaspiro[4.6]undecane was estimated to be 6.0 kcal/mol. The initiating activity of carbon black increased with an increase in carboxyl group content of carbon black. Furnace black that contained no carboxyl group was unable to initiate the polymerization. Furthermore, the carbon black lost the initiating ability of the polymerization upon the blocking of carboxyl group on the surface by the treatment with potassium hydroxide or diazomethane. Based on these results, it was concluded that carboxyl group on carbon black plays an important role in the initiation. During the polymerization, a part of the polymer formed was grafted onto carbon black: the grafting ratio was 10–30%. The mechanisms of initiation and grafting were discussed.     

超临界CO2在高分子合成与制备中的应用

介绍超临界二氧化碳流体作为介质在高分子合成与制备中的研究进展。文中表明，可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应，可用超临界二氧化碳溶胀聚合法制备梯度共混物。此外，超临界二氧化碳还可用于聚合物分级和聚合物微孔、微纤与微球材料的制备等，显示出超临界二氧化碳是一种对环境无污染且价廉的     

Kinetics of γ-ray polymerization of formaldehyde in the presence of carbon dioxide

A kinetic study of the γ-ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to ?17°C. Two modes of the polymerization, spontaneous and γ-ray polymerization, occur in this system. The γ-ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ-ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ-ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ-radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ-ray polymerization were also investigated.     

Cationic ring-opening isomerization polymerization of spiro orthocarbonates initiated by carbon black

The ring-opening isomerization polymerization of spiro orthocarbonates (SOC), such as 2,8-dimethyl-1,5,7,11-tetraoxaspiro[5.5]undecane ( I ), 8,10,19,20-tetraoxaspiro[5.2.2.5.2.2]-heneicosane-2,4-diene ( II ), and 8,10,19,20-tetraoxaspiro[5.2.2.5.2.2]heneicosane ( III ), initiated by carbon black was investigated. No polymerization of SOC was initiated in the absence of carbon black. But in the presence of channel black having a carboxyl group, the polymerization of SOCs was initiated at 90–150°C to give the corresponding polyether carbonates. The initiating ability of carbon black increased with an increase in its carboxyl group content. Furnace black having no carboxyl group failed to initiate the polymerization. Based on these results, it was concluded that the carboxyl group on carbon black is capable of initiating the polymerization of SOC. During the polymerization, a part of the polymers formed was grafted onto carbon black surface via the termination of growing polymer chains. The percentage of grafting increased with an increase in conversion and reached about 55%. Furthermore, polyether carbonate-grafted carbon black was found to produce a stable colloidal dispersion in chloroform. The mechanism of initiation and grafting were discussed.     

Liquid carbon dioxide as a solvent for the radiation polymerization of ethylene

The usefulness of liquid carbon dioxide as a solvent for polymerization of ethylene was studied. The effect of liquid carbon dioxide on the polymerization was investigated under conditions of the pressure of 400 kg./cm.² over the temperature range 20–45°C. by using γ-radiation and AIBN as initiators. The infrared spectrum of the polymers showed that carbon dioxide had little effect on the polymer structure. The polymers contained no combined carbon dioxide and only small amounts of vinylidene unsaturation. The methyl content of the polymers was 0.5–4.0 CH₃/1000C. The polymer yield and molecular weight were found to be decreased by the addition of carbon dioxide in both polymerization by γ-radiation and AIBN. The number of polymer molecules formed per unit time increased with the content of carbon dioxide in the γ-ray polymerization, and was constant in the case of AIBN. The advantages of the use of liquid carbon dioxide as a solvent in this polymerization were also considered from the viewpoints of the continuous process, the separation of polymer, the stability of carbon dioxide to radiation, and commercial applications.     

超临界二氧化碳中含氟聚合物的合成*

超临界二氧化碳是廉价、低毒、不易燃、易回收、环境友好的惰性聚合介质,是传统有机溶剂的替代品。尤其是有望成为含氟单体的聚合溶剂,以替代目前使用的氟氯烃。本文详细地介绍了近年来以超临界二氧化碳为介质的氟烷基丙烯酸酯类单体和氟烯烃类单体的聚合反应研究,其中涉及氟烷基丙烯酸酯类单体的均聚和共聚,可熔融加工的四氟乙烯聚合物,离子交换树脂,偏氟乙烯的均聚和共聚合等。研究表明在超临界二氧化碳中的含氟单体的聚合反应有其它溶剂体系无法比拟的优点。     

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.     

Cationic Grafting of Vinyl Polymers onto a Carbon Whisker,Initiated by Acylium Perchlorate Groups Introduced onto the Surface

Abstract

The cationic graft polymerization of vinyl monomers onto a carbon whisker, vapor-grown carbon fiber, initiated by acylium perchlorate groups introduced onto the surface, was investigated. The introduction of acylium perchlorate groups onto a carbon whisker was achieved by the treatment of a carbon whisker having acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride, with silver perchlorate in nitrobenzene. It was found that the cationic polymerization of vinyl monomers, such as styrene, indene, N-vinyl-2-pyrrolidone, and n-butyl vinyl ether, is initiated by acylium perchlorate groups on a carbon whisker. In the polymerization, the corresponding vinyl polymers were grafted onto a carbon-whisker surface based on the propagation of polymer from the surface: the percentage of grafting of polystyrene and polyindene reached 42.5 and 100.3%, respectively. The percentage of polystyrene grafting decreased with increasing polymerization temperature because of preferential chain transfer reactions at higher temperatures. Polymer-grafted carbon whisker gave a stable colloidal dispersion in a good solvent for grafted polymer.     

The Effect of Carbon Dioxide on the Alkali-Metal Initiation of Polyisoprene

The structures of polymers formed when alkali metals are placed in the vapor phase above isoprene monomer, both in the presence and absence of carbon dioxide, were investigated. In the absence of carbon dioxide, the polymers were all gel-like and soluble. In the presence of carbon dioxide, however, insoluble popcorn polymers were formed. The structures of the soluble polymers varied from primarily cis in the case of lithium to trans for sodium and potassium initiation. In the presence of carbon dioxide the three alkali metals produced polymers having similar structures, predominantly trans. In the absence of carbon dioxide most of the polymerization proceeds anionically with the majority of the free radical sites of the initially formed radical anion being removed by a transfer reaction or by dianion formation. The presence of carbon dioxide, however, leads to the formation of car boxy late ions that prevent anionic polymerization. Then, due to the structural orientation of the radical anion on the surface, free-radical polymerization occurs, leading to microgelation and popcorn polymerization. This results from cross-linking caused by mechanical rupture of the growing chains.     

“LIVING-LIKE” CATIONIC POLYMERIZATION OF ISOBUTYL VINYL ETHER INITIATED BY CARBOXYL GROUPS ON CARBON BLACK SURFACE/ETHYLALUMINUM DICHLORIDE SYSTEM IN THE PRESENCE OF 1,4-DIOXANE

The effect of 1,4-dioxane as an added base on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on carbon black surface/ethylaluminum dichloride (EtAlCl₂) system was investigated. Although the cationic polymerization of IBVE by carbon black/EtAlCl₂ system the absence of 1,4-dioxane instaneously proceeded and the monomer conversion achieved 100% within a minute. The molecular weight distribution (MWD) of polyIBVE obtained was very broad. On the contrary, the MWD of polyIBVE obtained was very narrow and narrower than that obtained from the carbon black/ZnCl₂ initiating system by the addition of 1,4-dioxane. The number-average molecular weight (Mn) of polyIBVE obtained was directly proportional to monomer conversion in the cationic polymerization. However, the Mn of polyIBVE obtained from the polymerization by the initiating system in the the presence of 1,4-dioxane was smaller than that of the calculated value, assuming that polyl(IBVE) chain forms per unit carboxyl group on carbon black surface. It was concluded that carbon black/EtAlCl₂ initiating systems in the presence of 1,4-dioxane has an ability to initiate “living-like” cationic polymerization of IBVE based on the above results. PolyIBVE was grafted onto a carbon black surface after quenching the above “living-like” cationic polymerization systems with methanol.     

Radical Graft Polymerization of Vinyl Monomers Initiated by A20 Groups Introduced Onto a Carbon Black Surface: Effect of azo Groups on Graft Polymerization

The radical graft polymerization of vinyl monomers from carbon black initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto carbon black surface was achieved by three methods: the reaction of 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP) with (1) epoxide groups, which were introduced by the reaction of carbon black with chlorometh-yloxirane; (2) acyl chloride groups, which were introduced by the reaction of carboxyl groups on the surface with thionyl chloride; and (3) 3-chloroformyl-1-cyano-1-methylpropyl groups, which were introduced by the reaction of carbon black with 4,4′-azobis(4-cyanovaleric acid) and then thionyl chloride. The amount of azo groups introduced onto the surface by the above methods was determined to be 0.07-0.19 mmol/g. The graft polymerization of methyl methacrylate was found to be initiated by azo groups introduced onto the carbon black surface. During the polymerization, poly(methyl methacrylate) was effectively grafted onto carbon black through propagation of the polymer from the radical produced on the surface by the decomposition of the azo groups. The percentage of grafting using carbon black having azo groups introduced by method 1 increased to 40%. It was also found that the graft polymerization of several vinyl monomers such as styrene, acrylonitrile, and acrylic acid was initiated by the azo groups introduced onto the surface and the corresponding polymer was effectively grafted onto the surface. Furthermore, the effect of the amount of carbon black having azo groups on the graft polymerization was investigated.     

Studies of the polymerization of diallyl compounds. XXII. Polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures

The polymerization of diallyl oxalate was conducted in the presence of radical initiators at a high temperature range of 80–180°C; a large decrease in degree of polymerization, an increase in residual unsaturation of the resulting polymer, and the evolution of carbon dioxide were observed with the elevation of temperature. These findings were reasonably interpreted by considering the dismutation of the uncyclized growing radical to yield the allyl radical, carbon dioxide, and polymer carrying a terminal double bond. The kinetics of the polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures were also discussed in detail.     

Metal-containing initiator systems. IV. Polymerization of methyl methacrylate by systems of some activated metals and organic halides

A study of the polymerization of methyl methacrylate initiated by the binary systems of some activated metals and organic halides has been made. It was found that the initiator activities of these systems were greatly dependent on the kind and the preparation or activation method of the metals (i.e., oxidation potential, surface area, and purity), and also on the kind of organic halides (i.e., bond-dissociation energy of their carbon–halogen bonds). From the kinetic studies of the polymerization at 60°C with the system reduced nickel–carbon tetrachloride, the rate of polymerization was found to be proportional to the monomer concentration and to the square root of concentration of both nickel and carbon tetrachloride at the lower concentration range of carbon tetrachloride, indicating that the system induced the radical polymerization. A similar conclusion was also obtained from the copolymerization with styrene with this system at 60°C, i.e., the resulting copolymer composition curve was in agreement with that obtained with azobisisobutyronitrile (AIBN). The apparent overall activation energy for the methyl methacrylate polymerization with this system was estimated to be 7.5 kcal/mole, which was considerably lower than that with AIBN. On the basis of the results obtained, an initiation mechanism for the polymerization with these initiator systems is presented and discussed.     

丙烯酸在炭黑表面接枝聚合研究

丙烯酸在炭黑表面接枝聚合研究吴壁耀，刘安华，邵兰英，蒋子铎（武汉化工学院精细化工系，武汉，４３００７３）关键词接技聚合，炭黑，Ｚｅｔａ电位，表面改性炭黑是由大量的原生粒子聚集而成的．该聚集体表面积大、表面又含有丰富的极性基因，故在炭黑／涂料树脂体系中...     

Graft Polymerization of Vinyl Monomers Onto Carbon Black by Use of the Redox System Consisting of Ceric Ions and Carbon Black Carrying Alcoholic Hydroxyl Groups

The radical graft polymerization of vinyl monomers onto carbon black initiated by a redox system consisting of ceric ion and carbon black having alcoholic hydroxyl groups was investigated. The introduction of alcoholic hydroxyl groups onto the carbon black surface was achieved by the reaction of carbon black with alcoholic hydroxyl radicals, formed by the reaction of alcohol with benzoyl peroxide. The rate of the polymerization of acrylamide (AAm) initiated by the redox system was found to increase in the following order of hydroxyl groups: 1-hydroxyoctyl < 1-hydroxypropyl < 1-hydroxyethyl < hydroxymethyl < 1-hydroxy-1-methylethyl. In the redox polymerization, poly-AAm was effectively grafted onto carbon black by propagation of the polymer from the radical formed by the reaction of ceric ions with the alcoholic hydroxy groups. The percentage of grafting increased with increasing conversion. By use of this redox system, poly(acrylic acid), polyacrylonitrile, and poly(N-vinyl-2-pyrrolidone) could be grafted onto carbon black, but poly(methyl methacrylate) and polystyrene could not be so grafted. The graft polymerization of AAm by use of a redox system consisting of ceric ion and PVA-grafted carbon black was also investigated.     

Facile synthesis of polymers bearing cyclic carbonate structure through radical solution and precipitation polymerizations accompanied by concurrent carbon dioxide fixation

The radical polymerization of glycidyl methacrylate (GMA) was conducted under a carbon dioxide atmosphere (1 atm) in the presence of catalysts for the reaction of carbon dioxide and the oxirane group to afford the five‐membered cyclic carbonate group. The degrees of the carbon dioxide fixation depended on catalysts, concentration, and solvents. In solution reaction, the slower polymerizations resulted in faster carbon dioxide fixation, due to the faster carbon dioxide fixation to GMA than to oxirane moieties in polymers. When the polymerization was conducted in 1,4‐dioxane, which is a good solvent for polyGMA but a poor solvent for the analogous polymer bearing cyclic carbonate moieties, the resulting polymers were precipitated out as the progress of the polymerization and the carbon dioxide fixation. As a result, polymers could be isolated by simple filtration and rinsing with methanol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3170–3176, 2009     

Cationic polymerization of formaldehyde in liquid carbon dioxide. Part I

A cationic polymerization of formaldehyde which gave a high molecular weight polymer was studied in liquid carbon dioxide at 20–50°C. In the polymerization without any catalyst both the rate of polymerization and the molecular weight of the resulting polymer increased rapidly with a decrease in the loading density of the monomer solution to the reaction vessel, and also increased with an increase in the initial monomer concentration. From these results it was concluded that the initiating species could be ascribed to an impurity contained in the monomer solution. Both the rate of polymerization and the degree of polymerization of the polymer also increased with rising temperature. The carboxylic acid added acted as a catalyst in the polymerization because of increase in the polymer yield, the molecular weight of polymer formed, and the number of moles of polymer chain with increasing dissociation constant of acid used. It was concluded that the polymerization in liquid carbon dioxide proceeded by a cationic mechanism. Methyl formate had no influence on the polymerization, but methanol and water acted as a chain-transfer agent.     

Living cationic polymerization of isobutyl vinyl ether by the carboxyl group of the carbon black/zinc chloride initiating system

The effect of zinc chloride (ZnCl₂) on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on a carbon black surface was investigated. Although the polymerization of IBVE was initiated by carboxyl groups on the surface, the rate of polymerization was small and the molecular weight distribution (MWD) of poly IBVE was very broad. The rate of the polymerization was found to be drastically increased, and 100% monomer conversion was achieved in a short time by the addition of ZnCl₂. The number-average molecular weights (M_n) of the polyIBVE were directly proportional to monomer conversion in the polymerization initiated by the carbon black/ZnCl₂ system. By addition of the monomer at the end of the first-stage polymerization, the added monomer was smoothly polymerized at the same rate as in the first stage. The M_n of the polymer was in excellent agreement with the calculated value, assuming the polyIBVE chain forms per unit carboxyl group on the surface and MWD was narrow (M_w/M_n = 1.2 ～ 1.3). Based on the results, it is concluded that carbon black/ZnCl₂ system has an ability to initiate the living cationic polymerization of IBVE. Furthermore, it was found that polyIBVE was grafted onto the carbon black surface after the quenching of the living polymer with methanol. © 1995 John Wiley & Sons, Inc.