Anion exchange membranes prepared by amination of cross-linked membranes having chloromethyl groups with 4-vinylpyridine and trimethylamine

Copolymer membranes composed of chloromethylstyrene and divinylbenzene were reacted with 4-vinylpyridine and then trimethylamine to prepare highly tight anion exchange membranes. When 4-vinylpyridine reacted with chloromethyl groups of the copolymer membranes, 4-vinylpyridine polymerized in the membrane matrix to form a ladder-like polymer, of which one polymer was cross-linked. Consequently, relationships of ion exchange capacity and water content to electrical resistance of the obtained membranes were completely different from those of the anion exchange membranes with benzyl trimethylammonium groups cross-linked with divinylbenzene. With increasing reaction time of the copolymer membranes with 4-vinylpyridine, the electrical resistance of the membranes markedly increased with a small decrease in ion exchange capacity and with the decrease in water content. And fixed ion concentration of the membranes reacted with 4-vinylpyridine and then trimethylamine was higher than that of the membranes with benzyl trimethylammonium groups. These are thought to be because of the formation of a ladder-like polymer in the membrane matrix and the introduction of pyridine unit, which is more hydrophobic and bulkier than trimethylamine. The remarkable decrease in the pore size of the membranes was confirmed by the measurement of the diffusion coefficient of neutral molecules, urea and glucose, through the membranes.     

2-甲基-5-乙烯基吡啶的合成研究

以6-甲基烟酸甲酯为起始原料,经过还原、氧化、Wittig反应合成了标题化合物,3步总收率66.7%,产品经1HNMR和元素分析表征。该方法具有操作简单、成本低等优点,适合工业化生产。     

Molecular weight distribution of acrylonitrile-2-methyl-5-vinylpyridine copolymers

Conclusions A fractionation of an acrylonitrile-2-methyl-5-vinylpyridine copolymer with respect to composition and molecular weight has been carried out by the fractional precipitation method. The distribution of the copolymer with respect to composition has a bimodal character, which may exert an effect on the properties of solutions and fibres.The parameters and K in the Mark-Kuhn-Houwink equation have been determined by the sedimentation method; they are equal to 0.89 and 2.062×10^–4, respectively.Translated from Khimicheskie Volokna, No. 5, pp. 17–18, September–October, 1985.     

Syntheses and nonlinear optical properties of polymers prepared from chloromethylstyrene

The synthesis and characterization of new dyes, prepared in two steps from chloromethylstyrene, and containing azo moieties or stilbene are reported. All synthesized monomers show spectroscopic properties (nuclear magnetic resonance, ultravoilet) in accordance with the attempted structure. These monomers have been copolymerized with styrene and the nonlinear optical properties of the new compounds and those of previously described polymeric imines have been studied via second harmonic generation. © 1994 John Wiley & Sons, Inc.     

Preparation of microporous membranes from cation exchange membranes prepared by the paste method

A microporous membrane is prepared by treating the cation exchange membrane (Fe⁺⁺⁺ form) with an H₂O₂ aqueous solution. The cation exchange membrane is prepared by the paste method: the base membrane is prepared beforehand and then sulfonated. The preparative conditions of the base membrane were studied in connection with the characteristics of the resultant microporous membrane. Furthermore, the availability of the microporous membrane for ultrafiltration was studied by using an aqueous solution of a bovine hemoglobin.     

Benzoyl peroxide-induced graft polymerization of 2-methyl-5-vinylpyridine onto polyester/wool blend

Graft polymerization of 2-methyl-5-vinylpyridine (MVP) onto polyester/wool blended fabric was carried out using benzoyl peroxide as initiator. The graft polymerization reaction was conducted under a variety of conditions. The graft yield increased by increasing benzoyl peroxide concentration from 0.559 mmole/l. to 1.657 mmole/l. Further increase in benzoyl peroxide concentration (i.e., up to 2.795 mmole/l.) decreased grafting. Increasing the MVP concentration from 4% to 10% caused a significant enhancement in grafting. The same held true for raising the polymerization temperature within the range of 65°–85°C. The grafting reaction proceeded initially at a fast rate and decreased with time to a slower rate. The grafted samples showed improved dyeability toward acid dye, increased density, and decreased moisture regain as compared with the untreated blend. Furthermore, a tentative mechanism for initiation of grafting was suggested.     

Anion exchange resins prepared from polystyrene crosslinked via a Friedel–Crafts reaction

The preparation of anion exchange resins from polystyrene crosslinked via a Friedel–Crafts reaction is investigated. Chloromethylation of a highly swollen styrene–hexahydrotriacrylolyl-s-triazine copolymer with a mixture of chlorosulfonic acid and methylal is accompanied by the crosslinking of the initially flexible copolymer. The crosslinking efficiency is dependent on the conditions (temperature, nature of solvent) of chloromethylation and can be explained by cationic postpolymerization of polystyrene or poly(benzylchloride), which takes place concurrently with the chloromethylation.     

Relaxation properties of a chemisorption fiber based on the copolymer of acrylonitrile and 2-methyl-5-vinylpyridine

The relaxation properties of chemisorption fibers based on copolymers of acrylonitrile and 2-methyl-5-vinylpyridine synthesized in aqueous medium and in dimethyl sulfoxide were investigated. It was shown that the conditions of synthesis of the copolymers affect the relaxation properties of the fibers. It was hypothesized that the change in the relaxation properties is due to the composite composition of the copolymers, which is determined by the copolymerization constants.All-Russian Scientific-Research Institute of Polymer Fibers, Mytishchi. Translated from Khimicheskie Volokna, No. 4, pp. 36–39, July–August, 1992.     

ZSM-5 zeolite membranes prepared from a clear template-free solution

Template-free nanosized ZSM-5 seeds were prepared from commercially available ZSM-5 powder. By use of these seeds, thin and hydrophilic ZSM-5 zeolite membranes were prepared on the outer surface of a porous -alumina tube in a clear solution free from organic template. The membranes showed high thermal stability to withstand pretreatment at 400 °C. At 270 °C, the ideal selectivities for H₂/i-butane and N₂/SF₆ were 61 and 20, respectively. The membrane was effective to separate butane isomers at high temperatures. The maximum of the n/i-butane ideal selectivity was 36 at 300 °C. The separation factors for a 50/50 n/i-butane mixture were as high as 13 in the temperature range from 300 to 400 °C.     

Behavior under UV irradiation of new polymers with photocrosslinkable and NLO groups prepared from chloromethylstyrene

Summary In this paper, the syntheses of two styrene-based monomers bearing either an optical active group, Dispersed Red 1, or a photocrosslinkable cinnamate group are described. The study of their copolymerizations with maleic anhydride and the characterizations of the copolymers are given. Polymer materials with exposure to UV curing light, 254 nm, exhibit a photobleaching process. This feature can be used in the preparation of channelized wave-guide using photomask methods.     

Modification of transport properties of ion exchange membranes,XIII. Surface-modified cation exchange membranes prepared from polyamines and a copolymer membrane containing p-stryenesulfonyl chloride

A membrane precursor was prepared by the copolymerization of p-styrenesulfonyl chloride and divinylbenzene in the presence of a poly(vinyl chloride) supported cloth. The surface of the membrane was treated with various amines, and then the sulfonyl chloride groups in the internal part of the membrane were hydrolyzed with an aqueous sodium hydroxide solution in organic methanol or acetone solvent. Hydrolysis conditions were examined for the introduction of the sulfonic acid groups. The membrane modified by ethylenediamine exhibited slightly bipolar properties during the electrodialysis of seawater. Surface-modified membranes using tetraethylenepentamine exhibited excellent monovalent cation permselectivity, low membrane electric resistance, and long performance durability during the electrodialysis of seawater.     

Microstructure of cation exchange membranes prepared by the paste method

The microstructure of a cation-exchange membrane (Neosepta CL-25T) prepared by the paste method was investigated by microscopic examination, x-ray microanalysis, scanning electron microscopic observation, and determination of pore size distribution of the porous membrane obtained by selective decomposition of the cation-exchange resin component (R-resin) of the membrane. Both the cloth part and the other part were characterized by uniform distributions of the colloidal R-resin (under 0.1 μm) in poly(vinyl chloride) (PVC). This structural feature made it possible to understand comprehensively the properties of the cation exchange membranes prepared by the paste method. The mechanism of the formation of such microheterogeneity is explained in terms of the microphase separation of the styrene (St)–divinylbenzene (DVB) copolymer from PVC during polymerization.     

2-甲基吡啶合成2-乙烯基吡啶

以二苯胺生产过程中产生的副产物2-甲基吡啶为原料,以KOH改性的HZSM-5沸石分子筛为催化剂,气相一步法合成了2-乙烯基吡啶。考察了催化剂的焙烧温度、用于改性的钾含量、成型过程中的粘结剂的种类和含量,反应的工艺条件等因素对反应的影响。实验结果表明,催化剂焙烧温度为550℃,改性钾离子的质量分数为3%,以硅溶胶作为粘结剂进行催化剂成型,硅溶胶的用量为K-HZSM-5质量的50%,当反应温度为360~370℃,原料2-甲基吡啶和甲醛摩尔比为1∶3,质量空速0.75 h-1时,2-甲基吡啶的转化率可达到80.26%,2-乙烯基吡啶的选择性可达到97.59%,实现了副产物的有效利用。     

Factors affecting polymerization of 2-methyl-5-vinylpyridine in poly(ethylene terephthalate) fibers using benzoyl peroxide as initiator

Polymerization of 2-methyl-5-vinylpyridine (MVP) in the presence of poly(ethylene terephthalate) fibers (PET) using benzoyl peroxide (BP) as initiator caused a substantial increase in the weight of fibers. The mechanism of this polymerization is believed to be grafting by vinyl addition to PET radical formed under the influence of BP. Increasing the BP concentration up to 4.26 × 10^?3 mole/l. causes a significant enhancement in grafting, while further increase brings about a marked fall in the graft yield. Increasing the MVP concentration up to 10% also improves significantly the graft yield, but the latter, particularly in the later stages of the reaction, shows lower values at higher MVP concentrations. Raising the reaction temperature from 65° to 95°C causes a significant enhancement in the rate of grafting, though the maximum graft yield obtained at 95°C is much lower than at 85°C. Incorporation of Cu²⁺ ion in the polymerization system enhances the graft yield outstandingly. The same holds true for Fe³⁺ and Li ions, but the enhancement is much less than for Cu²⁺ ion. Addition of acetic or oxalic acid to the reaction decreases the magnitude of grafting. The same situation is encountered when a water/solvent mixture is used as reaction medium. Solvents employed were methanol, ethanol, propanol, and butanol. Also studied was the polymerization reaction with respect to homopolymer, total conversion, and graft efficiency.