V. S. Soldatov, E. Kosandrovich, T. V. Bezyazychnaya
{"title":"铵离子和四乙基铵离子形式的羧基离子交换剂在水中的异常膨胀","authors":"V. S. Soldatov, E. Kosandrovich, T. V. Bezyazychnaya","doi":"10.29235/1561-8323-2023-67-6-465-472","DOIUrl":null,"url":null,"abstract":"A fibrous carboxylic ion exchanger, obtained by post-radiation grafting of polyacrylic acid to polypropylene fiber, in the ammonium form has an abnormally low swelling in water, corresponding to 10 moles of water per equivalent, and in the form of tetraethylammonium ion (NEt4+) – abnormally high 25 moles of water/eq. Considering that NH4+ is a hydrophilic particle and NEt4+ is hydrophobic, this fact seems paradoxical. The article attempts to explain this phenomenon using molecular modeling (ab initio calculations of the structure of hydrate complexes in the HF MO LCAO approximation with the 6-31G basis set) in combination with the Predominant Hydrates Model, which made it possible to calculate the theoretical water sorption isotherms of the ion exchanger and compare them with experimental data. The abnormally low swelling of the ion exchanger in the NH4+-form is caused by the formation of a strong bond between the carboxylate anion and ammonium with a significant degree of covalence due to the superposition of the Coulomb interaction of the ions and the formation of a hydrogen bond between them. The abnormally high swelling of NEt4+-forms is caused by the absence of a strong interaction between cations and carboxylate groups due to the impossibility of their convergence due to steric reasons. The high swelling of the ion exchanger is caused by the absence of blocking of the hydrophilic carboxylate groups of the ion exchanger by hydrogen bonds with the cation. The ion exchanger matrix does not contain a cross agent and does not create a spatial restriction for the high swelling of the ion exchanger.","PeriodicalId":11283,"journal":{"name":"Doklady of the National Academy of Sciences of Belarus","volume":"60 5","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Abnormal swelling in water of carboxylic ion exchanger in the forms of ammonium and tetraethylammonium ions\",\"authors\":\"V. S. Soldatov, E. Kosandrovich, T. V. 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The abnormally low swelling of the ion exchanger in the NH4+-form is caused by the formation of a strong bond between the carboxylate anion and ammonium with a significant degree of covalence due to the superposition of the Coulomb interaction of the ions and the formation of a hydrogen bond between them. The abnormally high swelling of NEt4+-forms is caused by the absence of a strong interaction between cations and carboxylate groups due to the impossibility of their convergence due to steric reasons. The high swelling of the ion exchanger is caused by the absence of blocking of the hydrophilic carboxylate groups of the ion exchanger by hydrogen bonds with the cation. 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引用次数: 0
摘要
在聚丙烯纤维上通过辐照后接枝聚丙烯酸而获得的纤维状羧酸离子交换剂,以铵形式存在时,在水中的膨胀率异常低,相当于 10 摩尔水/当量,而以四乙基铵离子(NEt4+)形式存在时,膨胀率异常高,达到 25 摩尔水/当量。考虑到 NH4+ 是亲水性粒子,而 NEt4+ 是疏水性粒子,这一事实似乎自相矛盾。文章试图利用分子建模(在 HF MO LCAO 近似中利用 6-31G 基集对水合物复合物的结构进行 ab initio 计算)并结合 Predominant Hydrates Model(主要水合物模型)来解释这一现象,从而计算出离子交换器的理论吸水等温线,并将其与实验数据进行比较。NH4+ 形式的离子交换剂膨胀率异常低的原因是羧酸根阴离子和铵之间形成了强键,由于离子之间的库仑相互作用和氢键形成的叠加作用,羧酸根阴离子和铵之间形成了共价程度很高的强键。NEt4+ 形式的膨胀率异常之高,是因为阳离子和羧基之间没有强烈的相互作用,这是因为立体原因导致阳离子和羧基不可能聚合在一起。离子交换剂的高膨胀性是由于离子交换剂的亲水性羧酸基团与阳离子之间没有氢键阻隔。离子交换剂基体不含交叉剂,不会对离子交换剂的高膨胀性造成空间限制。
Abnormal swelling in water of carboxylic ion exchanger in the forms of ammonium and tetraethylammonium ions
A fibrous carboxylic ion exchanger, obtained by post-radiation grafting of polyacrylic acid to polypropylene fiber, in the ammonium form has an abnormally low swelling in water, corresponding to 10 moles of water per equivalent, and in the form of tetraethylammonium ion (NEt4+) – abnormally high 25 moles of water/eq. Considering that NH4+ is a hydrophilic particle and NEt4+ is hydrophobic, this fact seems paradoxical. The article attempts to explain this phenomenon using molecular modeling (ab initio calculations of the structure of hydrate complexes in the HF MO LCAO approximation with the 6-31G basis set) in combination with the Predominant Hydrates Model, which made it possible to calculate the theoretical water sorption isotherms of the ion exchanger and compare them with experimental data. The abnormally low swelling of the ion exchanger in the NH4+-form is caused by the formation of a strong bond between the carboxylate anion and ammonium with a significant degree of covalence due to the superposition of the Coulomb interaction of the ions and the formation of a hydrogen bond between them. The abnormally high swelling of NEt4+-forms is caused by the absence of a strong interaction between cations and carboxylate groups due to the impossibility of their convergence due to steric reasons. The high swelling of the ion exchanger is caused by the absence of blocking of the hydrophilic carboxylate groups of the ion exchanger by hydrogen bonds with the cation. The ion exchanger matrix does not contain a cross agent and does not create a spatial restriction for the high swelling of the ion exchanger.