Abstract

The paper presents the structural organization of the surface (selective) layer. The amorphous phase of the cellulose acetate composite membrane is formed at a certain stage of the technological cycle of producing the cellulose acetate membrane. It presents a mass of broken, entangled, and twisted macromolecular chains connected by a network of hydrogen bonds of various strengths. Analysis of the IR spectra, where the shapes of the absorption bands of the valence vibrations of hydroxyl groups at ν = 3339.14–3366.2 cm^–1 with the asymmetry coefficient varying from ~1 for a dry sample to 0.79 for a wet sample, suggests that the bulk supramolecular structure of the cellulose acetate layer of the air-dry sample is formed by two types of hydrogen bonds and the dipole–dipole interactions of the carbonyl groups. The interactions of macromolecules in the equatorial plane are formed by a network of hydrogen bonds of the OH…O type with the participation of a single hydroxyl group of the pyranose ring in cellulose acetate. In the axial direction, the supramolecular structure is organized through the hydrogen bonds of the CH…O=C type between the methane and carbonyl groups, as well as possibly the dipole–dipole interactions between the coplanar ordered dipoles of the C=O groups. The coefficient of asymmetry of the absorption bands of hydroxyl groups is reduced to 0.81–0.79 and the intensity of the absorption band of methyl groups is reduced by factors of 2.56, 3.3, and 3.8 in water-saturated samples due to the destruction of the supramolecular structure and the reorganization of the hydrogen bonds between the active groups of cellulose acetate and water molecules. The absence of an absorption band of ν = 873.53–851.9 cm^–1 in the water-saturated samples indicates a conformational rearrangement of the macromolecules into a linear form with the formation of narrow mesopores of cellulose acetate between the macromolecules.

中文翻译：

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振动光谱法研究组成膜中的醋酸纤维素表面层

摘要

本文介绍了表面（选择性）层的结构组织。乙酸纤维素复合膜的无定形相在生产乙酸纤维素膜的技术周期的特定阶段形成。它呈现出大量断裂，纠缠和扭曲的大分子链，这些链通过各种强度的氢键网络连接。红外光谱分析，其中在ν= 3339.14–3366.2 cm ^–1处羟基价振动的吸收带形状不对称系数从干样品的〜1变化到湿样品的0.79不等，表明风干样品的醋酸纤维素层的整体超分子结构是由两种类型的氢键和偶极-偶极相互作用形成的的羰基。大分子在赤道平面上的相互作用是由OH…O型氢键网络与醋酸纤维素中吡喃糖环的单个羟基参与而形成的。在轴向方向上，超分子结构通过甲烷和羰基之间CH…O = C类型的氢键以及C = O基团的共面有序偶极子之间的偶极子-偶极子相互作用来组织。羟基吸收带的不对称系数降低到0.81-0。由于超分子结构的破坏以及乙酸纤维素和乙酸纤维素的活性基团之间的氢键的重组，在水饱和的样品中甲基吸收带的强度降低了79、79％，甲基吸收带的强度降低了2.56、3.3和3.8倍。水分子。缺少ν= 873.53–851.9 cm的吸收带水饱和样品中的^–1表示大分子的构象重排为线性形式，大分子之间形成了乙酸纤维素的窄中孔。