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前文曾报导,以聚丙烯酰胺为母体,通过甲醛为桥梁引入二氰二胺可合成一种新型阳离子聚电解质,简称PAm·MG,它是一种弱聚碱的盐酸盐,结构式如下(S 为取代度):PAm·MG 对含活性艳红染料的废水有明显的絮凝脱色作用,其絮凝效果受聚合物的取代度、介质的pH 以及外加盐浓度的影响,而这些影响因素又直接与聚碱的离解行为或胺基离子化度(指已离子化的胺基占全部胺基的分数)密切相关.为此,本文对影响PAm·MG 离解行为和离子化度的一些因素作进一步探讨,并通过粘度测定考察离解行为对聚合物在水中形态的影响,为PAm·MG 的实际应用提供理论根据. 相似文献
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疏水相互作用对阳离子聚电解质与染料键合的影响 总被引:5,自引:0,他引:5
用平衡渗析法研究了阳离子聚电解质PAm·MG 和P(St-Am·MG)与甲基橙(MO)及P(St-Am·MG)与MO的同系物乙基橙(EO)、橙武Ⅳ(O-Ⅳ)在25、35、45和55 ℃下相互作用的热力学. 由K1otz方程, 求得键合常数K_1和热力学参数ΔG、ΔH及ΔS. 含疏水基的P(St-Am·MG)与MO的键合能力比不含疏水基的PAm·MG 强. P(St-Am·MG)与不同染料作用时, 键合程度为O-Ⅳ>EO>MO, 即染料的疏水性越强, 与高聚物的作用程度越大.键合体系加入脲或甲醇, 疏水相互作用受到破坏, 导致高聚物与染料之间的键合受到削弱. 相似文献
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以P(St-Am·MG)对染料活性艳红(X-3B)溶液进行絮凝试验,考察了高聚物剂量及外加盐对絮凝效果的影响,并与无疏水基团的阳离子聚丙烯酰胺PAm·MG的絮凝能力进行了比较。发现絮凝体系无外加盐时,高聚物与染料的作用主要是通过静电力;有外加盐时,高聚物的电荷受到屏蔽,高分子链卷曲,PAm·MG的絮凝效果受到较大影响。而P(St-Am·MG)与X-3B之间存在疏水相互作用,受影响较小,此时P(St-Am·MG)的絮凝性能优于PAm·MG。用平衡渗析法研究了不同温度时甲醇和脲存在下P(St-Am·MG)与X-3B相互作用的热力学。证明了它们之间确实存在疏水相互作用。 相似文献
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以 AIBN为引发剂,丙烯酰胺与苯乙烯在1 4—二氧六环溶剂中进行共聚,得到无规共聚物P(St-Am)。使P(St-Am)与过量甲醛反应,生成羟甲基化产物。该产物在酸性条件下进一步与二氰二胺反应,制得分子链上同时含有离子和疏水基团的高分子苯乙烯—丙烯酰胺基甲撑脒基脲盐酸盐共聚物P(St-Am·MG)。P(St-Am) 和P(St-Am·MG) 的结构用红外光谱法鉴定,组成用元素分析法测定。 P(St-Am·MG) 在 MeOH/H_2O混合溶剂中的粘性行为表明它是带有疏水基的聚电解质,用电导滴定法和小角激光光散射法分别测定其电荷密度和分子量。 相似文献
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PAm-g-PMAA亲水性聚合物微球的合成 总被引:7,自引:0,他引:7
利用链转移自由基聚合和端基置换反应法 ,合成了苯乙烯基单封端的聚甲基丙烯酸叔丁酯 (PBMA)大分子单体 .在N ,N′ 亚甲基二丙烯酰胺 (Bis A)存在的条件下 ,使PBMA大分子单体与亲水性单体丙烯酰胺(Am)在乙醇 水的混合介质中进行分散共聚反应 ,得到了表面为PBMA接枝的聚丙烯酰胺 (PAm g PBMA)聚合物微球 .将所得PAm g PBMA微球在酸性条件下水解 ,得到了整体亲水的聚甲基丙烯酸接枝的聚丙烯酰胺(PAm g PMAA)聚合物微球 .用激光光散射、透射电子显微镜和X射线光电子能谱仪等对聚合物微球的直径、形态及表面组成进行了表征 .研究结果表明 ,在共聚反应中PBMA大分子单体的分子量与浓度、Bis A浓度和介质的组成对微球的形成与颗粒直径的大小有明显影响 ;所形成的聚合物颗粒是以PBMA为壳、以交联PAm为核的核壳结构微球 . 相似文献
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无助稳定剂十六醇(HD)时,以十八烷基双聚氧乙烯基苄基氯化铵(OEBA)为单一阳离子乳化剂,制备粒径为200 nm左右的D4细乳液.选OEBA浓度相同、有无HD添加的两对照D4细乳液,经KOH引发进行开环聚合,动态光散射法(DLS)追踪聚合中粒径变化过程.同时借助紫外可见分光光度计,考察合成的聚二甲基硅氧烷(PDMS)细乳液对强酸HCl、强碱KOH和电解质NaCl的相对稳定性.结果显示,单一乳化剂OEBA时,不但制备的D4细乳液稳定性良好,而且合成的PDMS细乳液具优良的耐强酸、强碱和电解质能力;单一乳化剂时不仅聚合中粒径变化与添加HD相一致,而且反应速率随转化率和时间的变化规律也相似. 相似文献
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不同脱乙酰度壳聚糖Mark-Houwink方程的订定 总被引:28,自引:1,他引:28
通过多步脱乙酰基反应和溶液超声波降解制备了脱乙酰度D.D在49—100%(wt),重均分子量在1.94—25.1×10~5的系列壳聚糖样品,在0.1mol/L CH_3COONa+0.2mol/L CH_3COOH溶剂中和30℃下,用光散射法首次订定出了不同D.D壳聚糖的M-H方程常数K和α值,结果如下:D.D(wt%) K×10~3(ml·g~(-)1) α69 0.104 1.1284 1.424 0.9691 6.589 0.88100 16.800 0.81导致K和α值差别的主要原因是由于壳聚糖大分子链上的胺基(—NH_2)被酸质子化后,失去了形成分子内氢键的能力,减弱了内旋转受阻程度,同时,质子化后形成的阳离子聚电解质分子链链段间以及链段与溶剂之间的相互作用增强,有效电荷密度的增加使得聚电解质溶液粘度增大。 相似文献
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Jacek Dutkiewicz 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):957-965
The reaction of polyacrylamide with formaldehyde was studied in a neutral aqueous medium at equal initial molar concentrations of amide groups and of formaldehyde (0.05 mol/L) and in a range of temperatures from 45 to 75°C. The process was investigated by measuring the loss of free formaldehyde in the reaction mixture and the changes of the sum of free formaldehyde and methylol groups versus time. The addition of HCHO to an amide function of the polymer leads to its N-methylol derivative which may transform into the product of condensation between the latter and another amide group. Because of high dilution of polyacrylamide macromolecules in the reaction mixtures studied, cross-linking of the polymer chains with formaldehyde is rather unlikely. Therefore the disappearance of the N-methylols formed is probably due to some intramolecular reactions. It is believed that they involve the condensation of N-hydroxymethyls with neighboring amide groups which results in cyclic structures containing methylenediamide sequences. The occurrence of intramolecular reactions was confirmed by applying Flory's theory of gelation. The addition of HCHO to amide functions is a rate-determining stage in the case of polyacrylamide. For this reaction the rate constants were estimated and the corresponding activation energy was found to be 62 kJ/mol. 相似文献
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The reaction between formaldehyde and the side-chain of tryptophan results in a methylol adduct. This methylol adduct formation also occurs during reductive methylation reactions. In the current study, we investigate the fragmentation pattern of peptides with N-terminal dimethylation and methylol adduction at the tryptophan side-chain. Once formed, the methylol group can easily undergo water loss to form an imine. The peptides with imine or methylol adduct on tryptophan exhibit similar MS/MS fragmentation patterns. We observed ions resulting from an intramolecular reaction between the dimethylamino group at the peptide N-terminus or the lysine side-chain and the imine group. This reaction reduces the imine to a methyl group. We also observed the loss of the imine adduct on tryptophan. This reaction is likely to occur through the reaction of an amino or hydroxyl group with the imine adduct followed by subsequent loss of methylenimine or formaldehyde. 相似文献
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A systematic quantum chemical study reveals the effects of chirality on the intermolecular interactions between two chiral molecules bound by hydrogen bonds. The methods used are second‐order Møller–Plesset perturbation theory (MP2) with the 6‐311++g(d,p) basis set. Complexes via the O? H···O hydrogen bond formed between the chiral 2‐methylol oxirane (S) and chiral HOOH (P and M) molecules have been investigated, which lead to four diastereomeric complexes. The nomenclature of the complexes used in this article is enantiomeric configuration sign corresponding to English letters. Such as: sm, sp. The relative positions of the methylol group and the hydrogen peroxide are designated as syn (same side) and anti (opposite side). The largest chirodiastaltic energy was ΔEchir = ?1.329 kcal mol?1 [9% of the counterpoise correct average binding energy De(corr)] between the sm‐syn and sp‐anti in favor of sm‐syn. The largest diastereofacial energy was ?1.428 kcal mol?1 between sm‐syn and sm‐anti in favor of sm‐syn. To take into account solvents effect, the polarizable continuum model (PCM) method has been used to evaluate the chirodiastaltic energies, and diastereofacial energies of the 2‐methylol oxirane···HOOH complexes. The chiral 2,3‐dimethylol oxirane (S, S) is C2 symmetry which offers two identical faces. Hence, the chirodiastaltic energy is identical to the diastereomeric energy, and is ΔEchir = 0.563 kcal mol?1 or 5.3% of the De(corr) in favor of s,s‐p. The optimized structures, interaction energies, and chirodiastaltic energies for various isomers were estimated. The harmonic frequencies, IR intensities, rotational constants, and dipole moments were also reported. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
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The title compound naphthalen-2-yl-4-methyl-1,2,3-thiadiazole-5-carboxylate (C 14 H 10 N 2 O 2 S,M r=270.31) was synthesized by the reaction of 4-methyl-1,2,3-thiadiazole-5-carbonyl chloride with 2-naphthol,and its structure was characterized by IR,1 H NMR,high-resolution mass spectrometry and single-crystal X-ray diffraction.The crystal belongs to orthorhombic,space group Pbcn with a=23.475(5),b=9.6640(19),c=10.814(2),β=90.00°,Z=8,V=2453.2(9) 3,M r=270.30,D c=1.464 g/cm 3,μ=0.262 mm-1,F(000)=1120,R=0.0444 and wR=0.1099.X-ray analysis revealed that the thiadiazole and naphthalene rings were non-planar,while the thiadiazole ring and the ester group were essentially planar,and two intermolecular hydrogen bonds C(6) H(6)···O(1) and C(14) H(14)···O(1) were observed.The preliminary biological test showed that the title compound had antifungal and antivirus activities against tobacco mosaic virus. 相似文献
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Jacek Dutkiewicz 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):877-885
Reactions of chitosan (degree of deacetylation 67%, weight-average molecular weight 850,000) with formaldehyde were performed in a dilute aqueous acetic acid solution at a molar ratio of amino groups of the polymer to HCHO of 0.06:O.1 mol/L and at different temperatures (45, 60, and 75°C). In each case the pH of the reaction mixtures was 3.4 during the experiments. The process was investigated by measuring the kinetic changes of the free formaldehyde concentration and the sum of free formaldehyde and methylol groups produced. No gelation of the reaction product was observed. The experimental results led to the conclusion that the methylol groups formed by the addition of HCHO to chitosan functions take part in some intramolecular reactions with amino and/or hydroxyl groups of chitosan. Initially, the concentration of the resultant methylene bridges grows rapidly and then drops again until an equilibrium is established. This rather unusual decomposition of the methylene links once formed without changing the reaction conditions is accompanied by a substantial growth of the amount of methylol derivative whose concentration at the beginning of the process increased rather slowly. 相似文献
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Shouta Kousaka Masanori Ito Shin‐Ichi Yusa 《Journal of polymer science. Part A, Polymer chemistry》2011,49(21):4586-4593
The photo‐induced association and dissociation of poly(sodium acrylate) containing a small amount of photoresponsive malachite green (MG) in aqueous solution were studied. It is known that MG dissociates into ion pairs under UV irradiation to produce the green triphenylmethyl cation. The cation thermally recombines with its counter anion to regenerate the colorless neutral compound. The random copolymer of acrylic acid with 0.05 mol % of MG monomer [P(A/MG0.05)] was soluble in aqueous 0.01 M NaCl at pH 12 as a unimer due to electrostatic repulsion between carboxylate pendent groups when the MG moieties were in the neutral form. On the other hand, these MG groups were converted to the cationic form on UV irradiation, leading to polymer aggregation driven by electrostatic interactions between the cationic MG and anionic carboxylate pendent groups. These aggregates could be dissociated by heating in the dark, as the cationic MG reverted to its neutral form, eliminating these attractive electrostatic interactions. The association and dissociation of the copolymer was monitored by dynamic light scattering (DLS). When the salt concentration in aqueous solutions of P(A/MG0.05) was increased from 0.01 to 0.5 M at pH 12, no aggregation was observed on UV irradiation because of ionic screening of the aforementioned electrostatic interactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
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The sulphide ion-selective electrode has been found to be applicable to the determination of thioacetamide in the concentration range of 10-1–10-3 M by direct potentiometry and titration with silver nitrate. The effects of the acid and alkali content of the solutions on the titration reaction have been studied. In alkaline and slightly acidic solutions the product of the reaction is silver sulphide; in solutions in which the acid concentration exceeds 0.5 M, a precipitate of silver thioacetamide is formed. If the alkali concentration of the solution is lower than that corresponding to the amount of acid formed during the titration, another potential jump occurs before the end-point owing to the decrease of sulphide'concentration governed by hydrolysis. 相似文献
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Phospholipase D from Streptomyces sp. AA586, PLDP, was modified with methoxypolyethylene glycol succinimidylsuccinate (ss-PEG), an active derivative of polyethylene glycol. By titration with trinitrobenzene sulfonate (TNBS), approximately 70% of the free amino groups in the enzyme protein were shown to be modified by treatment with ss-PEG. By this modification, the molecular weight of the enzyme was increased, judging from the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel filtration with Toyopearl HW-55F and TNBS titration. Due to loss of cationic charges, the enzyme protein became eluted faster in high performance liquid chromatography with CM-Toyopearl. By modification with ss-PEG, the enzyme became fairly thermostable, while pH-stability and optimal pH were not influenced. The value of Km for phosphatidylcholine of the hydrolytic reaction increased 2-fold, whereas that of the transphosphatidyl reaction was not significantly altered. 相似文献