PAE与丙烯酰胺接枝共聚改性的研究

利用溶液聚合的方法，使丙烯酰胺单体与不饱和聚酰胺多胺环氧氯丙烷树脂接枝共聚。在实验过程中，运用单体因素分析的方法，讨论了反应时间、引发剂用量、聚合单体丙烯酰胺的用量等主要因素对接枝共聚反应的影响。接枝后的聚丙烯酰胺树脂除了具有良好的湿拉伸强度性能外，还可以大幅度地提高纸张的干拉伸强度。     

APS-RH引发氯化二甲基二烯丙基铵与丙烯酰胺溶液共聚合反应

利用过硫酸铵-亚硫酸氧钠(APS-RH)引发体系,研究了聚合反应的温度、丙烯酰胺(AM)对氯化二甲基二烯丙基铵(DMDAAC)的物质的量比等因素以及几种不同的氧化-还原体系对DMDAAC-AM共聚反应规律的影响.在w(DMDAAC+AM)=30%;w(APS)=0.01%时,适宜的反应条件为:n(AM):n(DMDAA...     

The copolymerization of vinyl chloride with 1-olefins. I. A new method of investigation of the kinetics of homopolymerization and copolymerization of vinyl chloride

The indirect volumetric method following the amount of monomers in the heterogeneous liquid reaction mixture in a constant volume of samples periodically withdrawn by means of gas chromatography. This new method utilizes periodic sampling of the heterogeneous reaction mixture from the reactor during the reaction and gas chromatographic determination of the unreacted monomers contained in the sample. Its suitability and reliability were verified for the suspension homopolymerization of vinyl chloride. The reproducibility of sampling and the accuracy of determination of the degree of conversion and of the initial reaction rate were investigated. The conversion curves obtained by this method are compared with those obtained by the classical gravimetric method.     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution

The radiation-induced copolymerization of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water-insoluble copolymer. A water-soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation-polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.     

Mechanochemical block copolymerization in heterogeneous systems of the solid polyethylene with acrylamide aqueous solutions by ultrasonic irradiation

Summary Mechanochemical block copolymerization in heterogeneous systems of the solid polyethylene-acrylamide-sodium dodecyl sulfate aqueous solutions has been studied by ultrasonic irradiation at 30 °C. An additional effect of the solid polyethylene and the effects of acrylamide, and sodium dodecyl sulfate concentrations on mechanochemical block copolymerization were investigated. The block copolymerization of acrylamide was initiated by free radical produced from the polyethylene particles by ultrasonic waves. The rate of copolymerization R _p increased with increasing additional amount of polyethylene and that value was of the order of 10^-3 mol/l s. In addition, the R _p was given by R _p [Acrylamide] [Sodium dodecyl sulfate].     

木薯淀粉接枝丙烯酸-丙烯酰胺吸水剂合成研究初探

用过硫酸钾做引发剂,通过水溶液聚合法制得了木薯淀粉接枝丙烯酸和丙烯酰胺高吸水性树脂.研究了丙烯酸与丙烯酰胺用量比、反应温度及引发剂用量等对吸液性能的影响,分析了木薯淀粉在接枝前和接枝后的结构和性能.最佳反应条件为:丙烯酸/丙烯酰胺质量比1∶3,引发剂过硫酸钾用量是单体质量的0.125%,交联剂N,N'-亚甲基双丙烯酰胺的用量为单体质量的0.167%.反应温度为70℃,反应时间为4 h.     

丙烯酰胺与2-甲基丙烯酰氧乙基三甲基氯化铵共聚合竞聚率及Q-e值的研究

采用双官能度过氧化物-NaHSO3氧化还原引发剂,进行丙烯酰胺(AM:M2)与2-甲基丙烯酰氧乙基三甲基氯化铵(DMC:M1)的水溶液共聚合,制得了阳离子型聚丙烯酰胺P(AM-DMC),通过红外光谱对共聚物结构进行了表征;对聚合物进行元素分析得到氮的总含量并利用莫尔法对阳离子度进行了测定,运用不同的方法计算了单体的竞聚率,并对其值进行了比较,得到单体竞聚率的平均值r1=1.8641,r2=0.2637;运用Alfrey-Price方程计算得到了DMC的Q-e值.     

A kinetic study on copolymerization of styrene with methyl methacrylate in the presence of zinc chloride

The kinetics of copolymerization of styrene with methyl methacrylate in the presence of zinc chloride as a complexing agent at 50, 60 and 70°C and azobis-isobutyronitrile (AIBN) as an initiator was investigated by use of a dilatometer, modified to carry out reaction in an inert atmosphere. A ‘master graph’ has been prepared by which any volume contraction data could be converted into percentage conversion and the results used to calculate the rate of copolymerization (Rp). It has been observed that Rp is directly proportional to the concentration of initiator and methyl methacrylate but is inversely affected by the styrene concentration. Zinc chloride does not initiate the copolymerization reaction but increases Rp by increased the rate of propagation (Rp'). It does not affect either the rate of initiation (Ri) or the rate of termination (Rt) since the system attains a steady state. The rate constants and activation energy have also been calculated.     

Studies on the kinetics and mechanism of the copolymerization of acrylonitrile with styrene in the presence of zinc chloride

Radical copolymerization of acrylonitrile (AN) with styrene (Sty), using x,x′-azobisisobutyronitrile as initiator, was carried out in the presence of zinc chloride (ZnCl₂) dilatometrically at 65/pm 0.1 C for 120min. The rate of polymerization was a direct function of the concentrations of ZnCl₂, AN and Sty, and polymerization temperature. The viscosity-average molecular weight of the copolymer increased with ZnCl₂ concentration. The energy of activation in the presence and absence of the complex was evaluated as 82.5 kJ mol^?1 and 115.5 kJ mol^?1, respectively. The copolymerization of AN with Sty proceeded via the radical-complex mechanism.     

The copolymerization of vinyl chloride with 1-olefins. II. An investigation of the copolymerization reaction of vinyl chloride and propene

The conversion curve of the copolymerization of vinyl chloride with propene and the conversion curves of both monomers were determined, their initial reaction rates compared, and the copolymerization parameters determined by a method which utilizes periodical sampling of a heterogeneous reaction mixture from the reactor during the reaction and gas-chromatographic determination of unreacted monomers contained in the sample. The agreement between the final conversion values determined chromatographically and gravimetrically was evaluated by using results of a series of copolymerizations of vinyl chloride containing various amounts of propene in the initial monomeric mixture (5–30 wt %) carried out under the same conditions.     

丙烯酰胺与丙烯酸钠的辐射聚合及性能研究

以丙烯酰胺和丙烯酸钠为原料进行辐射聚合,并对聚合反应的剂量率、温度、辐照时间、单体用量对聚合反应的影响进行了研究,使用此聚合物对酒糟废液进行絮凝处理,处理后的糟水中悬浮物含量小于0.5g/L。聚合物的类型、加量、pH值、温度对处理效果都有很大影响。     

A study of sequence distribution of chloroprene and methyl methacrylate copolymers by 1H-NMR

The ¹H-NMR spectra of poly(chloroprene-methyl methacrylate) which was copolymerized with ethylaluminum dichloride (EtAlCl₂) and vanadyl trichloride (VOCl₃) were measured with the radical copolymers. The split signals of the OCH₃ and α-CH₃ protons in the spectra were assigned to triads and pentads with methyl methacrylate as a center, respectively, and the fomer concentrations were in reasonable agreement with the latter concentrations in triads. Moreover, it was found that the α-CH₃ signal was split into peaks of different tacticity when the mole fractional ratio of methyl methacrylate (MMA) to chloroprene (CP) in the copolymer was approximately 3.0 or greater.     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution. II. Copolymerization at higher monomer concentration

The radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide was studied to prepare a polymer flocculant that can be handled as a solid. The product obtained in the presence of 5–20% water was a solid and could be ground to a powder without drying. In order to obtain a water-soluble polymer at a higher concentration, the effect of various additives on the copolymerization was investigated and found that alcohols bearing a hydrogen atom attached to the tertiary carbon atom effectively inhibit intermolecular crosslinking to give water-soluble polymer. It is suggested that the formation of water-insoluble polymer is predominantly attributable to the crosslinking of polymer chains rather than to the imidation of amide groups. Copolymerization in the presence of isopropyl alcohol as inhibitor of the crosslinking was also studied and compared with that reported previously, which was carried out at a lower monomer concentration without additives.     

Effect of chain rigidity on block copolymer micelle formation and dissolution as observed by 1H-NMR spectroscopy

Amphiphilic copolymers poly(methyl methacrylate-b-acrylic acid), poly(methyl methacrylate-b-methacrylic acid), poly(methyl acrylate-b-acrylic acid) and poly(methyl acrylate-b-methacrylic acid) were prepared by reversible addition fragmentation chain-transfer (RAFT) polymerization. The hydrophilic polyacid blocks were either synthesized directly or formed by the hydrolysis of poly(tert-butyl acrylate) or poly(tert-butyl methacrylate) blocks. The hydrophobic blocks consisted of either the more rigid, high glass transition temperature (T _g ) poly(methyl methacrylate) or more flexible, low T _g poly(methyl acrylate) material. The hydrophilic blocks were either poly(methacrylic acid) (rigid, high T _g ) or poly(acrylic acid) (flexible, low T _g ). The micellization behavior of the polymers was studied by proton nuclear magnetic resonance (¹H-NMR) spectroscopy in mixtures of 1,4-dioxane-d₈ and D₂O. All four polymers were soluble in neat dioxane. In solutions of higher water content, the polymers with the more rigid hydrophobic blocks formed into micelles as was evidenced by broadening of the resonances resulting from the protons in those blocks. At moderate water concentration (25–50%), dissolution of the micelles was observed upon heating the solution. No micellization was observed in polymers containing the less rigid poly(methyl acrylate) hydrophobic block regardless of the identity of the hydrophilic block. As further evidence of micellization formation and dissolution, the spin-lattice (T ₁) and spin-spin (T ₂) relaxation times of protons in the hydrophobic and hydrophilic blocks were measured. Significant differences in the relaxation times as functions of temperature and solvent concentration were observed between the hydrophilic and hydrophobic blocks of the micelle-forming polymers.     

Solution conformation of endothelin determined by means of 1H-NMR spectroscopy and distance geometry calculations

The structure of endothelin-1 (ET-1), an endothelial cell-derivedpeptide with vasoconstricting activity, was determined in anaqueous solution by means of a combination of NMR and distancegeometry calculations. The resulting structure is characterizedby an -helical conformation in the sequence region, Lys9-Cys15.Furthermore, an extended structure and a turn structure existin the Cys1-Ser4 and Ser5-Asp8 regions respectively, and nopreferred conformation was found for the C-terminal part ofthe peptide which was not uniquely constrained by the NMR data.These structural elements, the -helical structure in the sequenceportion, Cys-X-X-X-Cys, and the extended structure in Cys-X-Cys,are homologous to those found commonly in several neurotoxicpeptides.     

AlCl_3-正丙醇催化1-十二碳烯烃与环己烯共聚反应的研究

采用三氯化铝作催化剂,对环己烯与1-十二烯烃的共聚反应进行了研究。考察了催化剂AlCl3的用量、异丙醇/AlCl3摩尔比、反应温度和反应时间对产品收率的影响。结果表明,最佳工艺条件为:催化剂三氯化铝的摩尔分数为4%,异丙醇/AlCl3摩尔比为0.5,反应温度为50～60℃,反应时间为6 h,环己烯∶1-十二烯烃=1∶4(摩尔比)。在最佳工艺条件下,可以合成100℃粘度为13.58 mm2/s,粘度指数为150,凝点为-35℃的聚烯烃合成油,收率为80%。具有粘度低、凝点低、粘度指数高的显著特点,是高质量的聚烯烃合成油。     

Polymerization of ionic monomers in polar solvents: kinetics and mechanism of the free radical copolymerization of acrylamide/acrylic acid

A precise data set describing the kinetics of the free radical copolymerization of acrylamide/acrylic acid (AM/AA) in the range of low total monomer concentration as a function of the pH, total monomer concentration, initiator concentration, and comonomer ratio is presented. Strong impact on the reactivity ratios has been identified for the pH and total monomer concentration. Specifically, at constant total monomer concentration of 0.4 mol/l and T=313 K the reactivity ratio of AM increases from 0.54 at pH 1.8 to 3.04 at pH 12. Contrarily, the reactivity ratio of AA decreases from 1.48 to 0.32. The crossover occurs at pH≈4.2. Electrostatic effects due to the variation of the degree of ionization of AA are primarily suggested to influence the kinetics. When the total monomer concentration increases from 0.2 to 0.6 mol/l at constant pH=12, the reactivity ratios of AM and AA decrease from 4.01 to 2.13 and increase from 0.25 to 0.47, respectively. Reduction of electrostatic repulsion between the ionized monomer AA and partially charged growing polymer chain ends due to higher ionic strength at higher total monomer concentration serves as explanation of the effect. The precise data set is the prerequisite for a novel approach to calculate copolymer compositions in case of variable monomer reactivity.     

A facile method of determination for distribution of the substituent in O-methylcelluloses using 1H-NMR spectroscopy

Summary A facile method to determine the distribution of methyl groups in regioselectively methylated celluloses on anhydroglucose unit was developed using solution ¹H-NMR analysis. The determination was deduced from the assignment of the signals of each proton, which directly attached to the glucopyranose ring carbon for partially methylated 2,3-di-O-methylcellulose samples observed in D₂O. These data for the distribution of the methyl groups corresponded to those based on the gas-chromatographic analysis. This method using the ¹H-NMR spectroscopy can facilitate the measurements of the distribution of methyl groups for randomly substituted and commercially available O-methylcelluloses. Received: 24 August 2000/ Revised version: 10 July 2001/ Accepted: 23 December 2001     

A study on the reaction kinetics of dendrimerization by FT-IR spectroscopy: Propagation of PAMAM dendrimer on silica gel

Solid-phase PAMAM dendrimer was synthesized by the repetitive addition of a branching unit to silica gel. All synthesis steps were monitored by infrared spectroscopy to investigate the reaction rate. Based on the measurements of infrared spectra, which showed the ester group varied as a function of reaction time, a reaction kinetics model was proposed and simulated. FT-IR and TGA measurements suggested that a ‘cross-linking’ reaction occurred in amidation process and generated structural defects, which decreased the grafted amount of dendrimer on silica gel. In addition, the analysis of reaction rate constants indicated that due to the formation of an intermediate, Michael addition of methyl acrylate to diamine was probably hindered by steric crowding. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.