Abstract

Different forms of 6-О-carboxymethyl chitin were prepared, namely, the salt form containing, the carboxy group in the –COONa form, the acid form containing the carboxy group in the –COOН form, and the mixed form containing the units in the acid and salt forms in the equimolar ratio. The composition and structure of the synthesized carboxymethyl chitin and films based on them were confirmed by Fourier IR spectroscopy, solid-state ¹³C NMR spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry. The mechanical properties of the films prepared from 6-О-carboxymethyl chitin in the salt and acid forms were evaluated by comparing their deformation characteristics. The Fourier IR data confirm formation of hydrogen bonds and ion pairs in 6-О-carboxymethyl chitin in the acid form as a result of intermolecular interaction of functional groups of the polymer. The solid-state ¹³С NMR data show that the substitution of the –СН₂СООNa group for hydroxyl proton in the course of the synthesis of 6-О-carboxymethyl chitin from chitin occurs exclusively at the С-6 atom of the glucopyranose ring. Comparison of the data of thermal gravimetric analysis and differential scanning calorimetry shows that the amount of water absorbed by the polymer depends on the form in which 6-О-carboxymethyl chitin occurs, with the salt form being the most hygroscopic. The deformation characteristics of films of 6-О-carboxymethyl chitin in the salt and acid forms were studied. The elastic modulus of 6-О-carboxymethyl chitin in the acid form significantly differs from that of 6-О-carboxymethyl chitin in the salt form. This difference may be due to higher content of water absorbed by the polymer in the films obtained from the salt form of 6-О-carboxymethyl chitin (20%) compared to the films obtained from the acid form of 6-О-carboxymethyl chitin (9%).

中文翻译：

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盐，酸和混合形式的羧甲基甲壳素的结构和性质

摘要

制备了6-О-羧甲基甲壳质的不同形式，即，盐形式包含-COONa形式的羧基，酸形式包含-COOН形式的羧基，以及混合形式包含-COOН形式的羧基酸和盐以等摩尔比形式形成。通过固态¹³傅里叶红外光谱确认了合成的羧甲基甲壳素的组成和结构以及基于它们的薄膜13 C NMR光谱，热重分析和差示扫描量热法。通过比较它们的变形特性，评估了由6--羧甲基甲壳素以盐和酸形式制备的薄膜的机械性能。傅立叶红外数据证实，由于聚合物官能团的分子间相互作用，酸形式的6-О-羧甲基几丁质中形成了氢键和离子对。固态¹³ СNMR数据表明，该-СН的取代₂由几丁质合成6-О-羧甲基几丁质的过程中，羟基质子的СООNa基团仅存在于吡喃葡萄糖环的С-6原子上。热重分析和差示扫描量热法的数据比较表明，聚合物吸收的水量取决于6-О-羧甲基甲壳质的形成形式，其中盐形式最易吸湿。研究了盐和酸形式的6-О-羧甲基几丁质薄膜的变形特性。酸形式的6-О-羧甲基几丁质的弹性模量与盐形式的6-О-羧甲基几丁质的弹性模量明显不同。