无皂乳液聚合法合成单分散性阴离子聚苯乙烯微球

采用无皂乳液聚合法制备了粒径大小可控且均一的聚苯乙烯微球,研究了反应过程中SDS加入量、反应温度、引发剂加入量及反应介质对聚苯乙烯微球粒径大小及分布的影响。利用傅立叶变换红外光谱仪对微球结构进行了表征。     

Rate of emulsion polymerization of styrene

In emulsion polymerization, the Smith and Ewart theory gives about two or three times the number of polymer particles obtained by experiment. In this paper, a reaction model is proposed which, from the standpoint of reactor design, can give an adequate explanation of the whole course of an emulsion polymerization of monomer highly insoluble in water. Among other things, the generating process of polymer particles is examined in detail. It is demonstrated experimentally that a new parameter proposed here, which represents the degree of difficulty of monomer initiation in micelles, is indispensable in explaining that process. Also confirmed is that monomer initiation takes place more easily in polymer particles than in micelles. According to the new model, the progress of polymerization, i.e., monomer conversion, the number of the polymer particles, and properties of polymer thus produced can be estimated with satisfactory accuracy. Furthermore, approximate equations are derived for easier estimation.     

Diffusion-controlled semibatch emulsion polymerization of styrene

Semibatch emulsion polymerization of styrene under the monomer-starved condition is strongly affected by the gel effect. A mechanistic model based on diffusion-controlled reaction mechanisms is developed to predict the kinetics of semibatch emulsion polymerization. Experimental data available in the literature are employed to assess the proposed model. Reasonable agreement between the model predictions and experimental data is observed. The simulation results suggest that the reaction system approaches Smith–Ewart case II kinetics (n? = 0.5) when the concentration of monomer in the particles is close to the saturation value, whereas the reaction system under the monomer-starved condition is characterized by diffusion-limited reaction mechanisms (n?≥0.5). © 1995 John Wiley & Sons, Inc.     

Anomalous particle through soap-free emulsion polymerization of styrene using oil-soluble initiator

One of oil-soluble initiators, VF-096, might work as cross-linker. This initiator would enable to synthesize the particle with cross-linking, which was involved with the particle morphology. Soap-free emulsion polymerization of styrene using this initiator was carried out to develop the method to control the particle morphology in one batch system. As a result, it was found that anomalous particle was generated without stirring and the particle morphology changed to be spherical by increasing shear stress through the stirring. One of the origins of the anomalous particle was the phase separation of the water in the particle and release of it from inside of the particle to the bulk.     

溴化苯乙烯/苯乙烯/丙烯腈乳液聚合试验条件探索

以过硫酸钾为引发剂,十二烷基硫酸钠为乳化剂,叔十二烷基硫醇为链转移剂,通过乳液法对溴化苯乙烯、苯乙烯、丙烯腈进行共聚得到溴化苯乙烯-丙烯腈共聚物.考察了引发剂、乳化剂、链转移剂的添加量,反应温度,反应时间,水和单体比例等对聚合反应收率的影响.研究表明：较适宜的反应条件为反应温度80℃,反应时间6h,水与单体质量比4∶1,引发剂质量为单体总质量的0.4％,乳化剂质量为单体总质量的4％,叔十二烷基硫醇为单体总物质的量的2％;上述条件下的产物收率高,相对分子质量4万左右,热分解温度高于350℃.     

Radiation-induced emulsion polymerization of vinyl acetate and styrene

Studies have been made of the γ-induced emulsion polymerization of styrene and comparisons made with chemically initiated emulsion polymerization. The polymerization proceeded smoothly to high conversions at 0 and 60°C, the reaction showing a high G (monomer) value. Complete conversions were obtained with total doses of less than 0.05 Mrad. In accordance with the behavior expected of systems having a constant rate of initiation, the molecular weight was found to decrease with decreasing temperature. The molecular weight and particle size distributions were narrower than those obtained in chemically initiated emulsion polymerizations at the same temperature. The radiation-induced emulsion polymerization of vinyl acetate proceeded smoothly at temperatures in the range 0–50°C to give polymers of much higher molecular weight than these obtained from chemically initiated polymerizations at the same temperature. Complete conversion was attained after a dose of 0.02 Mrad for latices approaching 50% solids. The elimination of ionic endgroups in the poly(vinyl acetate) radicals tends to drive the polymerization from the aqueous phase, resulting in faster rates and higher molecular weights than are obtained from chemically initiated systems. Rates of polymerization were found to be independent of temperature and the molecular weight of the polymer to be independent of dose rate. Latices of poly(vinyl acetate) of high solids content were evaluated for latex and film properties and found to have improvements over commercially available samples in both areas, especially in clarity of film and scrub resistance. A number of acrylate and maleate esters were copolymerized with vinyl acetate in a radiation-initiated emulsion system. High molecular weight copolymers were produced after low dose.     

Emulsifier‐free emulsion polymerization of styrene

Polystyrene latex particles in an emulsifier‐free emulsion were prepared by purified styrene (St) as monomer and 2,2′‐azobis (2‐amidino propane) dihydrochloride (ABA, 2HCl) as initiator. The optimized condition of polymerization of styrene was obtained by using the various parameters such as different amounts of monomer (0.009, 0.051, and 0.071 mol styrene/mol Water), different amounts of initiator (6.02, 4.62, 2.41, and 1.00 weight percent of initiator relative to styrene), and pH (range 1–7). Quantitative and qualitative analyses of prepared polymer were performed by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), and ¹H‐NMR and FT‐IR spectroscopy, that were used, respectively, to show the morphology of particles, the glass transition temperature (T_g), the average molecular weight, and the structure of the prepared polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1898–1904, 2004     

Continuous flow operation in emulsion polymerization of styrene

The kinetics of continuous emulsion polymerization of styrene were studied theoretically on the basis of the authors' batch reaction model, and a new reaction model was proposed for continuous operation. The validity of the model was tested by experiments conducted with stirred tank reactors in series. The characteristics of the first reactor used to generate polymer particles were studied in particular detail. It was found that there was an optimum residence time for the first reactor, the value of which was quantitatively predictable from the operating variables. The most suitable combinations of several types of reactors for continuous emulsion polymerization are also discussed.     

The stabilization effect of mixed-surfactants in the emulsion polymerization of styrene

Summary The emulsion polymerization of styrene was performed at 50°C with a mixture of anionic and nonionic surfactants using different surfactant concentrations. In the single-surfactant systems, a proportional relationship was observed between the total particle surface area per cm³ of aqueous solution at 90% conversion (TS) and the amount of surfactant used for each polymerization. For mixed-surfactant systems an additivity was established between the TS value and surfactant composition. The study of the particle size data from low to high conversion showed that the particle number changed with conversion.     

Kinetics of emulsion polymerization of styrene using the reactive surfactant HITENOL BC20

The effect of the reactive surfactant HITENOL BC20 (polyoxyethylene alkylphenyl ether ammonium sulfate; 20 U of ethylene oxide (EO)) on the emulsion polymerization of styrene was studied via reaction calorimetry (Mettler RC1; 70°C). For polymerizations carried out above the cmc of BC20, the reaction kinetics and evolution of the number of particles (N_p) resembled those reported using the conventional surfactant sodium lauryl sulfate, indicating that nucleation proceeded by a combination of micellar and homogenous nucleation (Interval I and Stage 2). The reaction rate (R_p) not only increased with increasing initiator (K₂S₂O₈) and surfactant concentrations, as expected, but the increase in rate in Stage 2 was dependent on the initiator concentration and independent of the surfactant concentration. This is consistent with the proposed nucleation mechanisms. The molecular weight increased with increasing surfactant concentration and decreasing initiator concentration as would also be expected for a conventional surfactant. The dependencies of R_p and N_p on the BC20 and initiator concentrations, however, were lower than the classical Smith‐Ewart values (R_p ∝ [E]^0.47–0.52; R_p ∝ [I]^0.21–0.25) although R_p was found to be directly proportional to N_p. Chain transfer to the reactive surfactant is considered a likely source of divergence. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effects of electrolyte concentration in the emulsion polymerization of styrene

Using concentrations below that required to coagulate the latex, the effects of the addition of potassium chloride on the emulsion polymerization of styrene have been investigated. When potassium decanoate (an emulsifier with a high critical micelle concentration (c.m.c.)) is used the increase in the concentration of micellar emulsifier and the decrease in the area occupied by an emulsifier molecule at the polymer/water interface are significant. When this is taken into account Gardon's equation for latex particle size reproduces the trend of the experimental results at the lower electrolyte concentrations. The agreement can be made quantitative by choosing alternative values for the propagation rate constant of styrene and the rate of radical formation from persulphate. With potassium octadecanoate (which has a low c.m.c.) and with potassium decanoate at the higher electrolyte concentrations these factors cannot account for the results observed.     

种子乳液聚合在PUA合成中的应用

系统地概述了种子乳液聚合合成聚氨酯－聚丙烯酸酯（PUA）复合乳液研究的各个方面，包括研究开发背景、基本原理，制备方法和工艺，产物和涂膜的结构和性能等。     

Soap-free emulsion polymerization of styrene using poly(methacrylic acid) macro-RAFT agent

A well-defined poly(methacrylic acid) (PMAA) macro-RAFT agent has been synthesized by the bulk polymerization using 4-toluic acid dithiobenzoate as a RAFT agent and successfully employed as a reactive emulsifier in the soap-free emulsion polymerization of styrene, leading to a formation of stable latex. The amphiphilic block copolymer, prepared from the in situ micelle formation, contains a hydrophilic PMAA block and a hydrophobic PS block, via styrene monomer transfer reaction to the dithioester function in PMAA macro-RAFT agent during the nucleation step. The chemical structure of the synthesized PS with the PMAA macro-RAFT agent was confirmed using FTIR and NMR. In addition, it was confirmed that the macro-RAFT agent is present on the particle surface via the ESCA measurement. The reaction mechanism was proposed that the stable spherical particles enlarged by the aggregation of small particles, which were also produced by the chemical or physical bonding between the tiny small particles. The results indicate that the PMAA macro-RAFT agent is used as emulsifier for the formation of PS particles and block copolymer [P(S-b-MAA)] in situ.     

Effect of stirring on the emulsion polymerization of styrene

The purpose of this paper is to clarify the effect of stirring on the course of emulsion polymerization of, for example, styrene. It establishes the existence of an optimum range of stirring speed and three important factors which must be considered in carrying out emulsion polymerization. (1) Stirring significantly affects the course of reaction in the presence of an imperfectly purified nitrogen atmosphere. Consequently, the number of polymer particles produced and the polymerization rate per particle will be affected. (2) At higher stirring speeds, polymer particles coagulate and coalesce. At lower stirring speeds, the reaction rate is controlled by the monomer transport rate from monomer droplets to the aqueous phase. (3) Stirring contributes to the reduction of the number of micelles because emulsifier molecules are adsorbed onto the surfaces of monomer droplets finely dispersed by the stirring. At low emulsifier concentrations near the critical micelle concentration, this effect cannot be neglected.     

A study of the soap-free emulsion polymerization of styrene

A study on the soap-free emulsion polymerization of styrene has been accomplished in this work. The polymerization reaction was carried out in a batch reactor under isothermal condition. Potassium persulfate was used as an initiator. In our experiments, the effects of agitation speed, monomer concentration, and initiator concentration on the number and size of polymer particles, on the conversion of monomer and molecular weight of polymers were investigated. In addition, the systems in the presence of emulsifier or CaSO₃ were investigated and discussed in comparison with a system free of them.     

Comparison of chemical and enzymatic emulsion polymerization of styrene

For the reasonable comparison of chemical and enzymatic polymerization, manganese(III) acetate and manganese peroxidase (MnP)‐catalyzed synthesis of polystyrenes were chosen and studied with respect to the yield and the polydispersity of polymer particles. MnP allowed the production of polystyrene in a higher yield and higher polydispersity (82.34% and 2.61) than manganese(III) acetate (77.90% and 1.75). This is believed to be due to a gradual supply of initiator radicals via a catalytic cycle in MnP‐catalyzed polymerization, whereas radicals are generated all at once in Mn(III)‐mediated polymerization. NMR spectroscopy revealed that atactic polystyrene was produced by emulsion polymerization using Mn(III) or MnP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

α-甲基苯乙烯和苯乙烯共聚物乳液的合成及性能研究

在不通N2的条件下,采用半连续法,在85℃、乳化剂用量为总量的7.53%时合成出了不同单体配比的α-甲基苯乙烯-苯乙烯共聚物[P(AMS-St)]乳液,其中AMS单体含量最高可达70%以上。用红外、核磁对共聚物结构进行了表征,讨论了加料方式、反应温度、乳化剂用量、单体配比对乳液转化率及稳定性的影响和单体组成与乳液流变性、乳胶粒径大小之间的关系。结果表明随单体中AMS含量的增加,乳液黏度逐渐变大,乳胶粒径逐渐变小,乳胶粒具有均一的尺寸。     

Surfactant-enhanced free radical polymerization of styrene in emulsion gels

The presence of a surfactant (such as hexadecyltrimethylammonium bromide, CTAB) enhanced the rate of polymerization of styrene in emulsion gels with and without silica. The emulsion gels consisted of styrene, azobisisobutyronitrile (AIBN), surfactant, water, and, in some cases, fumed silica. Polymerization of the emulsions was carried out at room temperature in one or several days depending on the composition of the emulsion. The conversion of monomer to polymer could exceed 90% in a couple of days. In contrast, very little polymerization occurred in the absence of surfactant. A simple model, incorporating a surfactant-initiator complex and standard free radical polymerization, successfully fits the experimental kinetics data. This analysis suggests that the initiator is complexed with approximately three surfactant molecules.     

Effect of 1-pentanol on the styrene emulsion polymerization

The influence of 1-pentanol (C₅OH) on the ST emulsion polymerization mechanisms and kinetics is investigated. The CMC of the ST emulsions first decreases rapidly and then levels off when the C₅OH concentration ([C₅OH]) increases from 0 to 72 mM. The effect of C₅OH increases to a maximum and then decreases when the SDS concentration ([SDS]) increases from 2 to 18 mM. At [SDS]=2 mM, homogeneous nucleation controls the polymerization kinetics regardless of [C₅OH]. At [SDS]=4 mM, the effect of [C₅OH] appears due to the transition from homogeneous nucleation to a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) occurs when [C₅OH] increases from 0 to 72 mM. The effect of [C₅OH] is the strongest at [SDS]=6 mM since the particle nucleation mechanisms span homogeneous nucleation (low [C₅OH]), a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) (medium [C₅OH]) and micellar nucleation (high [C₅OH]). At [SDS] >6 mM, in which micellar nucleation controls the polymerization kinetics, the effect of [C₅OH] decreases rapidly with increasing [SDS].