Abstract

The structural organization of the surface (active) layer and the state of water in composite ultrafiltration membranes have been investigated by means of the methods of vibrational IR spectroscopy and differential scanning calorimetry (DSC). Analysis of the shape of the absorption band of stretching vibrations of hydroxyl groups at ν = 3366.2 cm^–1 with an asymmetry coefficient of ~1 and the activity of vibrations of methyl groups with ν = 2884.02 and 2942.35 cm^—1 has demonstrated that the bulk supramolecular structure of a cellulose acetate layer of a dry sample is formed by two types of hydrogen bonds and dipole–dipole interactions of carbonyl groups. The interaction of macromolecules in the equatorial plane is formed by a lattice of hydrogen bonds of the (OH…O) type with participation of the only hydroxyl group of a pyranose ring in cellulose acetates. In the axial direction, the supramolecular structure is organized by hydrogen bonds between methine and carbonyl groups of the (CH…O=C) type and dipole interactions of coplanar ordered dipoles of (C=O) groups. The decrease in the intensity and the coefficient of asymmetry down to 0.81 of the absorption band of hydroxyl groups and the absorption band of methyl groups with frequencies ν = 2884.02–2942.35 cm^–1 by 2.56 and 3.3 times in water-saturated samples occurs due to the destruction of the supramolecular structure and the reorganization of hydrogen bonds of active groups of cellulose acetate and water molecules blocking intermolecular interactions of the macromolecules. The manifestation of hydroxyl groups with frequencies of 3302.7 and 33 105 sh cm^–1 and ν = 3600.6 and ν = 3598.8 sh cm^–1 on the absorption band indicates the interaction of associated water molecules of the bound and capillary forms. The absence of the absorption band with ν = 873.53 cm^–1 in the water-saturated sample is explained as an empirical indicator of the conformational transition of macromolecules into a linear form. Deconvolution of the endothermic peak on the DSC curve in the temperature range from 50 to 110°C into five Gaussians has demonstrated the multilevel structural organization of water molecules sorbed in pores and between macromolecules of the amorphous phase.

中文翻译：

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复合超滤膜表面层的结构组织和水分状态的研究

摘要

通过振动红外光谱和差示扫描量热法（DSC）研究了复合（超滤）膜表面（活性）层的结构和水的状态。在不对称系数为〜1的ν= 3366.2 cm ^–1处的羟基拉伸振动吸收带的形状和在ν= 2884.02和2942.35 cm ^-1处的甲基振动的活度分析已经证明，干燥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羰基的偶极-偶极相互作用形成的。大分子在赤道平面上的相互作用是由（OH…O）型氢键的晶格与醋酸纤维素中吡喃糖环的唯一羟基共同参与形成的。在轴向方向上，超分子结构由（CH…O = C）型次甲基和羰基之间的氢键和（C = O）基共面有序偶极子的偶极相互作用组成。频率ν= 2884.02–2942.35 cm ^–1时，强度下降和不对称系数下降到0.81的羟基吸收带和甲基的吸收带由于超分子结构的破坏以及醋酸纤维素和水分子的活性基团氢键的重组阻碍了大分子的分子间相互作用，在水饱和的样品中发生了2.56倍和3.3倍的相互作用。在吸收带上出现频率为3302.7和33 105 sh cm ^–1且ν= 3600.6和ν= 3598.8 sh cm ^–1的羟基表示结合态和毛细管形式的相关水分子之间的相互作用。ν= 873.53 cm ^–1时没有吸收带将水饱和样品中的α离子解释为大分子向线性形式构象转变的经验指标。DSC曲线上的吸热峰在50至110°C的温度范围内反卷积为五个高斯分布，证明了吸附在孔中和非晶相大分子之间的水分子具有多层结构。