Comparisons of styrene ionomers prepared by sulfonating polystyrene and copolymerizing styrene with styrene sulfonate

As part of a continuing study of ion-containing polymers, a comparison has been made on styrene-based sulfonate ionomers obtained by two different processes. Copolymers of styrene with sodium styrene sulfonate (SSS) have been compared with corresponding polymers obtained by the sulfonation/neutralization of preformed polystyrene (S–PS). The former system covered a range of sulfonate level from 1 to 30 mol %, while the latter ranged from about 1 to 7 mol %. The characterization of these materials has been conducted using solubility behavior, dilute solution viscometry, thermal mechanical analysis, density measurements, and water adsorption studies. At low (ca. 1%) levels the solubility behavior of the SSS copolymers and the sulfonated polystyrenes were similar. However, at higher sulfonate levels the solubility behavior in different solvents and the dilute solution viscometry were significantly different for the two systems. Similarly, thermal analysis studies (DSC) showed that the glass transition of the sulfonated polystyrene increased linearly with sulfonate level, while the T_g for the SSS copolymer increased modestly, up to about 7 mol % sulfonate content, and then remained constant. Significant differences in the softening behavior and water absorption characteristics were also observed for these two classes of ionomers. Although molecular weights and molecular weight distributions are not now available for these ionomers, the differences in their behavior does not appear to be due simply to differences in molecular weight. It is postulated that the differences in the copolymer and the S–PS ionomers may originate with differences in sulfonate distribution. It is suggested that the SSS monomer units are incorporated as blocks in the copolymer as opposed to a more random distribution in the S–PS ionomer. Indirect evidence in support of his argument is found, for example, in the case of the copolymer in the solubility behavior, the relative independence of T_g on sulfonate concentration and the apparent existence of a second, high temperature transition tentatively attributable to an ion-rich phase. Additional studies are required to confirm this hypothesis.     

The emulsion copolymerization of styrene and sodium styrene sulfonate

The emulsion copolymerization of styrene and sodium styrene sulfonate has been shown to be a feasible preparative route to ionomeric sulfonated polystyrene. The properties of these copolymers are reported elsewhere. The copolymerization rate was found to be dramatically enhanced when compared to that for the emulsion copolymerization of styrene under identical conditions. This copolymerization was studied in detail and two mechanisms were proposed to account for these rate differences. An increase in the number of polymerizing particles in the copolymerization with consequent rate enhancement was substantiated by electron microscopy. However, the data indicate that the rate differences cannot be fully accounted for by this effect. In addition, a gel effect is proposed as a second contributor to the enhanced rate. This gel effect is believed to result from the intermolecular association of the incorporated metal sulfonate units in the growing polymer particles. When a third monomer that plasticizes the ionic interactions is used the polymerization rate decreases. This supports the gel effect hypothesis.     

Emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate

The kinetics of the emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate have been examined over a range of comonomer compositions. The rate of polymerization was found to increase dramatically in the presence of small amounts of sodium styrene sulfonate. This increase is attributed to the increased number of particles formed when sodium styrene sulfonate was present and to a gel effect enhanced by ion association. At low concentrations of functional comonomer, where a monodisperse product was obtained, a homogeneous nucleation mechanism of particle generation is proposed. At higher concentrations, broader and then bimodal size distributions were obtained, and this is ascribed to significant aqueous phase polymerization of sodium styrene sulfonate. The water-soluble homopolymer is supposed to act as a locus of polymerization. The occurrence of this aqueous phase side reaction and the generation of secondary particles makes impossible the preparation of highly sulfonated polystyrene latexes by batch or seeded batch emulsion copolymerization.     

Effect of styrene oligomers on syndiospecific polymerization of styrene

Styrene oligomers, preferentially consisting of styrene dimers and trimers, are formed by a free radical mechanism at the thermal polymerization of stabilizer-free styrene during storage and at higher polymerization temperatures. The identity of several dimer and trimer fractions formed in such a free radical polymerization, their influence on a coordinative polymerization reaction, the syndiospecific polymerization of styrene, as well as their effect on the properties of the resulting polymers has been investigated.Styrene dimers and styrene trimers reduce the polymerization activity of the transition metal catalyst significantly, especially at low amounts of oligomers added to the styrene. This behavior is discussed with respect to a proposed mechanism involving complexation of the active transition metal species with the specific oligomer instead of the styrene monomer, resulting in increased steric hindrance towards insertion of a styrene molecule to the active site.Both oligomers reduce the molecular weight of the syndiotactic polystyrene, by acting as chain-transfer agents. The constancy of the polydispersity over the whole concentration range of added dimer or trimer indicates that the uniformity of the active sites of the coordinative polymerization is not significantly influenced by the presence of the oligomers.The thermal properties of the polymers demonstrate that the oligomers do not affect the high syndiospecificity of the active catalytic sites, whereas the increase in crystallization temperature with increasing amounts of styrene dimer or trimer is comparable to effects observed by the addition of crystallization nucleators to semicrystalline polymers.     

Gold-promoted styrene polymerization

Styrene can be polymerized at room temperature in the presence of equimolar mixtures of the gold(III) complexes (NHC)AuBr3 (NHC = N-heterocyclic carbene ligand) and NaBAr'4, in the first example of a gold-induced olefin polymerization reaction.     

气相色谱法同时测定苯乙烯催化氧化反应液中的苯乙烯、环氧苯乙烷和苯甲醛

建立了同时测定苯乙烯催化氧化反应液中的苯乙烯、环氧苯乙烷和苯甲醛的气相色谱分析方法。该法以正庚烷为内标物,在DB-1毛细管色谱柱上进行分离,氢火焰离子化检测器。方法的回收率98%~101.5%,相对标准偏差小于2.0%。     

Micellization of styrene/butadiene/styrene block copolymers in mixed solvents

Dilute solutions of three block copolymers, styrene/butadiene/styrene in the mixed selective solvents dioxane/different alcohols is studied at different temperatures. The molecular weight, second virial coefficient and radius of gyration in all selective solvents are also determined. From these measurements it is concluded that a maximum in the dissymmetry of the system for all the selective solvents used is observed. This maximum is observed at higher temperatures for concentrated solutions. Similarly, this maximum is also shifted to lower temperature by using strong precipitants in selective solvents. The milky opalescence is observed for all the selective solvents either by lowering the temperature of the system or by increasing the ratio of the precipitant in the selective solvent.     

Microemulsion polymerization of styrene

Initiation of polymerization in styrene oil-in-water microemulsions by water-soluble potassium persulfate of oil-soluble 2,2′-azobis-(2-methyl butyronitrile) at 70°C gave stable latexes which were bluish and less translucent than the original microemulsions. The effects of initiator concentration, polymerization temperature, and monomer concentration on the kinetics, particle size distributions, and molecular weight distributions were investigated. The kinetics of polymerization were measured by dilatometry. In all cases, the polymerization rate shows only two intervals, which increased to a maximum and then decreased. There was no apparent constant rate period and no gel effect. A longer nucleation period was found for polymerizations initiated by potassium persulfate as compared to 2,2′-azobis-(2-methyl butyronitrile). The small latex particle size (20–30 nm) and high polymer molecular weight (1–2 × 10⁶) implies that each latex particle consists of two or three polystyrene molecules. The maximum polymerization rate and number of particles varied with the 0.47 and 0.40 powers of potassium persulfate concentration, and the 0.39 and 0.38 powers of 2,2′-azobis-(2-methyl butyronitrile) concentration, respectively. This is consistent with the 0.4 power predicted by Smith–Ewart Case 2 kinetics. Microemulsion polymerizations of styrene–toluene mixtures at the same oil-water phase ratio gave lower polymerization rates and lower molecular weights, but the same latex particle size as with styrene alone. A mechanism is proposed, which comprised initiation and polymerization in the microemulsion droplets, by comparing the kinetics of microemulsion polymerization with conventional emulsion and miniemulsion polymerization systems.     

Ruthenium-catalyzed methoxycarbonylation of styrene

Methoxycarbonylation of styrene in the presence of homogeneous Ru catalysts is reported for the first time. Available Ru₃(CO)₁₂ together with halide source such as [bmim]Br, NaBr or LiCl represents active and easy to handle methoxycarbonylation catalyst. The key advantage of the new catalytic systems over traditional Pd catalysts is their high activity at CO pressure as low as 5 bar.     

Polymerization of styrene miniemulsions

Polymerization of styrene miniemulsions, prepared using a mixed emulsifier system comprising sodium lauryl sulfate and cetyl alcohol, was carried out using both water-soluble (potassium persulfate) and oil-soluble [2,2′-azobis-(2-methyl butyronitrile)] initiators. The effects of variation of initiator concentration, polymerization temperature, and added inhibitor on the kinetics and particle-size distributions were investigated to obtain more quantitative evidence concerning the locus of polymerization in miniemulsion systems. Experimental results for the kinetics and particle-size distributions clearly showed that monomer droplets became the main source of polymer particle formation. This was attributed to the fact that stable emulsions with droplet diameters in the range of 0.05 to 0.15 μm were produced using this mixed-emulsifier system. In this size range, droplet initiation could effectively compete with other mechanisms due to their large surface area. Their size was indeed similar to the corresponding latex particle size obtained after polymerization.     

Dispersion photopolymerization of styrene

Photopolymerization of styrene was carried out in a dispersed system to obtain 10 μm particles, using d-t-butylperoxide as initiator and poly(vinyl alcohol) as protective colloid. It was shown that particles typical for latex polymerization are also formed and interfere with the dispersion polymerization when excess protective colloid is used.     

Syndiospecific polymerization of styrene

The current development of the metallocene-based catalysts for syndiotactic polystyrene (SPS) has been reviewed. SPS is a new semi crystalline engineering thermoplastic with a crystalline melting point of 270°C. Because of its crystalline nature, SPS has high heat resistance, excellent chemical resistance and water/steam resistance. In this review, some mechanistic models for polymerization and stereoregulation, as well as the factors which affect the activity and stereospecificity of the catalysts, are discussed.     

Sulfonated polystyrene ionomers prepared by emulsion copolymerization of styrene and sodium styrene sulfonate

Sulfonated polystyrene (S–PS), which is of considerable scientific and technological interest, has been traditionally prepared by the sulfonation of preformed polystyrene. This report describes the preparation and properties of S–PS prepared by emulsion copolymerization of styrene and sodium styrene sulfonate. S–PS prepared by copolymerization gave solubility, solution behavior and thermal characteristics that are consistent with an ionomeric structure. The solubility characteristics indicated some chain-to-chain sulfonate heterogeneity. Thermal analysis studies indicated that the glass transition does not increase with increasing sulfonate content. This is contrary to what has been observed for S–PS prepared by sulfonation and suggests that the S–PS prepared by copolymerization is fundamentally different in structure than S–PS prepared by sulfonation of polystyrene.     

Coiodination of styrene with commercial clays: a convenient preparation of styrene oxide

Abstract  Styrene oxide is easily prepared in 82–91% yield by the reaction of styrene with iodine/water in the presence of commercial clays, followed by in situ addition of KOH in n-hexane/water. Graphical abstract        

Coiodination of styrene with commercial clays: a convenient preparation of styrene oxide

Abstract  

Styrene oxide is easily prepared in 82–91% yield by the reaction of styrene with iodine/water in the presence of commercial clays, followed by in situ addition of KOH in n-hexane/water.     

高表面电荷密度单分散苯乙烯磺酸钠纳米微球的制备

利用无皂乳液聚合 ,在苯乙烯 (St)的反应体系中引入适量的苯乙烯磺酸钠 (NaSS)参加共聚合 ,在聚合过程中分两阶段加料 ,第一阶段中NaSS浓度是决定乳胶粒粒径及单分散性的关键因素。当反应达到较高转化率 ( >90 % )时加入第二阶段单体混合物 ,此阶段中NaSS与St的比例决定了最终胶粒的表面电荷密度。利用上述两阶段无皂乳液聚合法成功地制备了粒径小于 10 0nm、单分散性指数小于 1.0 5以及表面电荷密度大于 3 0 μC·cm-2 的一系列乳胶粒     

Studies on styrene phosphonic acid

Some properties of styrene phosphonic acid (SPA) were studied. The crystals were triclinic, witha=0.6434 nm,b=0.5842 nm,c=2.0338 nm, =96.17°, =97.33°, =79.65° andZ=4. SPA underwent a change in crystal structure at 78.8°C, the hydrocarbon network became disordered (liquid-like) at 138.5°C. Crystals melted at 148.6°C giving a cubic mesophase, then changed to an isotropic liquid at 155.6°C and at 162.13°C SPA underwent decomposition. Values for pK₁=2.15 and pK₂=7.66 were obtained at 25°C. The water solubility of SPA at several temperatures, and its interaction with surfactant micelles were determined.     

Dioxygen-coupled oxidative amination of styrene

Dioxygen-coupled oxidative amination of olefins is an attractive, but challenging, catalytic transformation. The present work describes the first general method for intermolecular oxidative amination of aryl olefins with molecular oxygen as the stoichiometric oxidant. This palladium-catalyzed reactivity is compatible with several different nitrogen nucleophiles, including oxazolidinone, phthalimide, pyrrolidinone, and p-toluenesulfonamide. The presence of a catalytic quantity of a Br?nsted base in the reaction increases the catalytic activity and switches the reaction regioselectivity.