Kinetics of dispersion polymerization of dimethyl diallyl ammonium chloride and acrylamide

Dispersion copolymerization of dimethyl diallyl ammonium chloride with acrylamide has been investigated by the dilatometer technique using the mixture of poly(vinylpyrrolidone) and poly(dimethyl diallyl ammonium chloride) as the composite stabilizer and 2,2′-azobis(2-methylpropionconidine)dihydro chloride as the initiator. Monomer reactivity ratios of AM and DMDAAC were determined by the application of Fineman-Ross methods. The analysis of reactivity ratios revealed that DMDAAC is less reactive than AM, and copolymers formed are statistically in nature. The influences of the molar ratio of AM to DMDAAC, concentrations of monomers, stabilizer and initiator, etc. on polymerization rate and intrinsic viscosity of polymer have been examined. The rate of polymerization (R_p) can be represented by R_p μ [M]^1.44,R_p μ [S]^0.39,R_p μ [I]^0.60 {R_{\rm{p}}} \propto {[M]^{1.44}},{R_{\rm{p}}} \propto {[S]^{0.39}},{R_{\rm{p}}} \propto {[I]^{0.60}} . The overall activation energy for the rate of polymerization is 37.38 kJ/mol over the temperature range 35–55°C.Based on the experimental results, the polymerization mechanisms were discussed.     

丙烯酰胺与甲基丙烯酰氧乙基三甲基氯化铵反相乳液聚合动力学

以丙烯酰胺（AM）和甲基丙烯酰氧乙基三甲基氯化铵（DMC）为单体,失水山梨糖醇脂肪酸酯（Span 80）和失水山梨醇单油酸酯聚氧乙烯醚（Tween 80）为乳化剂,液体石蜡为油相,2,2'-偶氮二异丙基咪唑啉二盐酸盐（VA-044）为引发剂,研究AM与DMC反相乳液聚合动力学,反相乳液聚合速率方程为R_p=k[M]^2.12[I]^0.55[E]^0.65,AM与DMC反相乳液聚合表观活化能为80.65 kJ·mol^-1。通过反相乳液聚合速率随时间的变化关系得出其成核机理倾向于单体液滴成核。用Fireman-Ross法研究了共聚单体竞聚率,分别为r_AM=0.23、r_DMC=1.93,AM与DMC在聚合物链上发生无规共聚反应。单体量增大、引发剂量减少、乳化剂量增大、聚合温度降低均使共聚产物的特性黏数增大。     

Self-condensing vinyl polymerization of acrylamide

Summary A novel approach to branched polyacrylamide was described. The branched structure resulted from the amidyl radicals which were formed by the reaction of amide groups with Cu(III) of potassium diperiodatocuprate, K₅[Cu(HIO₆)₂], in alkaline medium and capable of initiating the vinyl polymerization of acrylamide monomer. The obtained polymer was characterized by ¹H NMR, FT-IR and intrinsic viscosity measurements. Received: 8 January 1999/Revised version: 26 May 1999/Accepted: 25 June 1999     

RAFT polymerization of hydrophobic acrylamide derivatives

Several hydrophobic acrylamide derivatives: the N-tert-butylacrylamide (TBAm), the N-octadecylacrylamide (ODAm) and the N-diphenylmethylacrylamide (DPMAm) have been polymerized by reversible addition-fragmentation chain transfer (RAFT) process in the presence of azobis(isobutyronitrile) (AIBN) and tert-butyl dithiobenzoate (tBDB) as initiator and reversible chain transfer agent (CTA), respectively. Homopolymerizations were compared as regards to kinetics and molecular weight (MW) control, and the results were discussed according to the monomer structure and to the influence of several experimental parameters, such as the [CTA]/[AIBN] ratio and the [Monomer]/[CTA] ratio. TBAm and ODAm monomers exhibited a well controlled polymerization (polydispersity index (PDI) below 1.3 for number average molecular weight (M_n) until 30,000 g mol⁻¹) over a wide range of conversion (until 70%), whereas DPMAm conversion remained below 20% partly due to steric hindrance. The molecular weights of several poly(TBAm) samples determined by four independent analytical techniques, size exclusion chromatography/on-line light scattering detector (SEC/LSD), ¹H NMR, ¹³C NMR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), were in agreement, close to the theoretical ones. Moreover, the MALDI-TOF MS analyses suggested the presence of parasite chains resulting from irreversible termination onto RAFT intermediate radicals.     

Electrochemically induced redox polymerization of acrylamide

Polymerization of acrylamide (AA) has been studied in aqueous solution in the presence of a Ce(IV) salt–oxalic acid initiator system in an electrochemical cell with and without separation of anolyte and catholyte. For reactions that required the cathode and anode sections to be analyzed individually, a cell whose compartments were divided by a sintered glass disk of the medium porosity was employed. Polymerization was initiated by a free radical that is formed by the fast reaction of oxalic acid and Ce(IV). The electrolysis of the reaction solution results in regeneration of Ce(IV), which can oxidize oxalic acid to produce radicals. The effect of sulfuric acid and cerium (IV) salt concentration and temperature on the yield of electroinitiated polymerization in different cell designs and structural identification of products were performed. Reaction was also followed by cyclic voltametric measurements, and a mechanism was proposed. Results indicated that the electrolysis method with a divided cell (85% conversion) shows advantages, compared with nonelectrolytic (5% conversion) and with undivided electrochemical cell (25% conversion) methods where a high concentration of initiator was used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 861–869, 1999     

丙烯酰胺微乳液聚合条件的研究

采用微乳液聚合方法合成了相对分子质量大于1000万的速溶聚丙烯酰胺(PAM).研究了聚合条件对产物分子质量的影响,诸如单体浓度、引发剂、温度、pH值、氨、脲及乳化剂的用量对PAM分子质量的影响,并用傅里叶变换红外光谱和扫描电镜对聚合物进行了表征,分析了产品速溶原因.     

Aqueous dispersion polymerization of acrylamide with quaternary ammonium cationic comonomer

Using aqueous solution of ammonium sulfate as medium, acrylamide (AM) and dimethylaminoethyl methacrylate methyl chloride (DMC) as main raw materials, poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and 2,2′‐azobis (2‐amidinopropane) dihydrochloride (V‐50) as initiator, the cationic polyelectrolyte of P(DMC‐AM) was synthesized by aqueous dispersion polymerization. The effects of the major reaction variables on synthesis conditions, product characteristics (particle size and molecular weight), and polymerization rate were investigated. The polymerization was retarded by the presence of the ammonium sulfate. The optimum reaction conditions for obtaining a stable aqueous dispersion were concentrations of 1.8 × 10^?4–7.0 × 10^?4 mol L^?1 for V‐50, 1.5–3.5% for stabilizer, and 23.2–30.0% for salt. The molecular weight of PDMC formed was 1.5 × 10⁵ to 7.0 × 10⁵. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Graft polymerization of acrylamide onto UV-irradiated films

Graft polymerization of acrylamide was attempted onto the surface of films preirradiated with UV radiation. The films employed are nylon 6, polypropylene, and ethylene–vinyl acetate copolymers. Following UV irradiation in air on films without photosensitizer, they were placed in monomer solution, degassed, and then heated to 50°C to effect the graft polymerization. After rigorous removal of homopolymers, polyacrylamide chains were found to be grafted in the surface region of the films to amounts up to several hundred micrograms per square centimeter of films. An ESCA study revealed the UV-irradiated but not yet grafted surfaces to be oxidized, and formation of peroxides was strongly suggested by the reaction of irradiated films with 1,1-diphenyl-2-picrylhydrazyl. It is likely that the initiator responsible for the graft polymerization is peroxides generated at and near the film surfaces upon UV irradiation. The grafted films became very slippery when contacted with water, in contrast with the films UV-irradiated but not yet grafted.     

丙烯酰胺水溶液聚合反应的研究

探讨了聚乙二醇作为分散剂时丙烯酰胺水溶液聚合体系中单体含量、还原剂用量对聚合物分子量的影响，并探讨了聚合时间与转化率、单体含量与聚合体系粘度之间的关系。结果表明，在保持聚合体系能够流动的前提下，单体含量可提高到２０％，聚合物的分子量可达３００万以上。     

Solution polymerization of acrylamide to high conversion

The solution polymerization of acrylamide initiated by 4,4′-azobis-4-cyanovaleric acid (ACV) at high monomer concentrations in the temperature range 25–50°C has been studied. Molecular weight distributions were measured by gel permeation chromatography and by electron microscopy. Molecular weight measurements show that transfer to monomer plays a dominant role in controlling the molecular weight averages.     

Kinetics of radical polymerization

Summary The effect of N-nitroso compounds on free radical polymerization has been studied in the temperature range of 30–70 °C. The comparison with the effect of C-nitroso compounds shows that not only the inhibitor effectivity but the inhibition mechanism are different in the case of N-nitroso compounds. The detailed kinetic investigations proved that the thermal dissociation product of N-nitroso compounds can act as scavengers of macroradicals.     

辛烷/Span80-Tween60/丙烯酰胺/水反相微乳液聚合动力学

对辛烷／Ｓｐａｎ８０－Ｔｗｅｅｎ６０／丙烯酰胺／水反相微乳液聚合的研究表明,其反应速度快,不到３０ｍｉｎ单体转化率即可达９０％以上。聚合过程中基本不存在恒速期,聚合速率在转化率接近２０％时达到峰值后随即迅速下降。通过进一步考察单体浓度（［Ｍ］）、引发剂浓度（［Ｉ］）、乳化剂浓度（［Ｅ］）、乙酸钠浓度以及反应温度对转化率为５％时的聚合速率（Ｒｐ,５％）和最大聚合速率（Ｒｐ,ｍａｘ）以及聚合物平均相对分子质量（Ｍｖ）的影响,得到如下动力学关系式：Ｒｐ,５％∝［Ｍ］１．０２［Ｉ］０．４５［Ｅ］－０．３…     

Effect of ultrasound on electrochemically initiated acrylamide polymerization

Acrylamide was polymerized under different voltages with ammonium persulfate as the initiator at room temperature. The polymerization reactions were performed in two different ways. In one case, the reaction was performed in a classical, three‐electrode electrochemistry cell, and in the other, the cell was placed in an ultrasonic bath, and ultrasound was applied during the reaction. Both reactions were performed at room temperature. The conversion was rapid; even in the normal electrochemical case, the composite rate constant was comparable to the case with free‐radical polymerization of acrylamide at 50–70°C. When ultrasound was applied, the conversion values increased more. The heterogeneity index and molecular weights of the polymers produced with and without ultrasound were measured with size exclusion chromatography. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 83–89, 2002; DOI 10.1002/app.10233     

Oxidation of petroleum sulphides with nitrogen dioxide

• 1.1. Petroleum sulphides (obtained as concentrates from appropriate distillates) were oxidized with a mixture of air and nitrogen dioxide to sulphoxides, with yields of 75 to 80% for sulphoxide sulphur, but the process was complicated by secondary processes: the formation of up to 30% of nitrosulphoxides of variable structure; sulphones and carbonyl compounds were present as traces. The target product was separated from most impurities by an alkaline wash, followed by chromatography.
• 2.2. Oxidation of individual sulphides under the conditions adopted gave sulphoxides, which contained only traces of compounds with a nitro-group, easily removed by recrystallization or elution chromatography.

     

不对称醚存在下丁二烯负离子聚合动力学

研究了以丁基锂为引发剂，4种新型不对称醚为调节剂，环己烷为溶剂的丁二烯负离子均聚。结果表明，4种新型不对称醚（GBSE，GBIE，GBCE，GBPE）均未发现有失活现象存在，且它们对丁二烯聚合速率的影响由大到小依次为：GBIE，GBSE，GBCE，GBPE。     

紫外激发丙酮-乙二醇引发丙烯酰胺聚合

探讨以丙酮-乙二醇（Acetone-EG）复配作为新型光引发剂,紫外引发水溶性单体丙烯酰胺（AM）进行自由基聚合。测定引发体系水溶液的紫外吸收光谱,分析了聚合过程的影响因素,得出丙酮与EG复合后紫外波长在240～295 nm范围内有较强吸收,光聚合最佳条件为：引发体系中丙酮与EG的质量比1∶1,引发剂总量为2 mL/L,单体水溶液质量分数为30%～35%,EDTA用量为0.04%,紫外辐射时间为60～80 min。聚合过程单体转化率为95%～97%,PAM黏均分子量可达(5.5～7.5)×106。     

Kinetics of catalyzed and non‐catalyzed soot oxidation with nitrogen dioxide under regeneration particle trap conditions

BACKGROUND: For compliance with the regulations on diesel particulate matter, car manufacturers have developed diesel particulate filters (DPF). These technologies require a regeneration method which oxidizes soot deposits in the filter. In diesel exhaust emissions there are two suitable oxidizing gases: oxygen and nitrogen dioxide. Nitrogen dioxide is much more active than O₂ and can directly attack the carbon surface. This work describes the kinetics of the oxidation of soot by NO₂ over a wide range of conditions relevant for DPF. RESULTS: The catalyzed and the non‐catalyzed oxidation of soot have been performed in a fixed‐bed reactor. The experimental results show that the overall oxidation process can be described by two additive parallel reactions: a direct C ? NO₂ reaction catalyzed by H₂O and a cooperative C ? NO₂ ? O₂ reaction catalyzed by the Pt/Al₂O₃ catalyst. The results obtained allow to propose the following kinetic law for the specific rates of the catalyzed and the non‐catalyzed oxidation of soot in the regeneration filter conditions: CONCLUSION: The kinetic parameters describing the oxidation rate of soot by NO₂ over a range of temperature and gas composition have been obtained. The extracted kinetics data are relevant for modeling the removal of trapping soot in automotive gas exhaust technology. Copyright © 2009 Society of Chemical Industry