阴/阳离子Gemini表面活性剂复配体系的泡沫稳定性调控及构效关系研究

doi:10.11949/0438-1157.20250682

摘要/Abstract

摘要：

阴/阳离子Gemini表面活性剂复配体系在改善泡沫稳定性方面表现出显著协同效应，但其作用机制尚未完全阐明。通过表面张力与分子动力学模拟相结合的方法，系统研究了不同阴/阳离子Gemini表面活性剂复配体系在气/液界面的自组装行为及其界面性质。结果表明，胺基与阴离子极性基间的静电作用与几何构象适配效应，保证了极性基区域的紧凑构型；而尾链间的构象优化与长度相容性，则促进了尾链区域的有序堆积。这些分子间的协同作用共同主导了复配表面活性剂在气/液界面形成致密且高度有序的吸附层，并显著增强了极性基的水合作用。由此形成的强化水化层及界面结构延缓了泡沫液膜的排液速度，进而赋予泡沫优异的机械强度和抗扰动能力，从而显著提升其宏观稳定性。

关键词: 分子模拟, 泡沫, 表面活性剂, 复配体系, 自组装, 协同作用

Abstract:

Mixed anionic/cationic Gemini surfactant systems exhibit significant synergistic effects in improving foam stability, yet their underlying mechanism has not been fully elucidated. Herein, through a combined approach of surface tension measurements and molecular dynamics simulations, the self-assembly behavior of different mixed anionic/cationic Gemini surfactant systems at the air/water interface and their interfacial properties were systematically investigated. The results indicate that electrostatic interactions between amine groups and anionic polar groups, along with geometric matching, ensure a compact configuration in the polar group region. Meanwhile, conformational optimization and length compatibility between tails promote ordered packing in the hydrophobic tail region. These intermolecular synergistic effects cooperatively cause the mixed surfactants to form a dense and highly ordered adsorption layer at the air/water interface, and significantly enhance the hydration of the polar groups. The resulting enhanced hydration layer and interfacial structure retard the drainage rate of foam films, which in turn endows the foam with superior mechanical strength and resistance to perturbations, thereby significantly improving its macroscopic stability.

Key words: molecular simulation, foam, surfactants, mixed system, self-assembly, synergism

中图分类号:

TQ 423.9

白阳, 姚舒爽, 徐梦旭, 赵靖雨, 于福顺. 阴/阳离子Gemini表面活性剂复配体系的泡沫稳定性调控及构效关系研究[J]. 化工学报, DOI: 10.11949/0438-1157.20250682.

Yang BAI, Shushuang YAO, Mengxu XU, Jingyu ZHAO, Fushun YU. Study on foam stability regulation and structure-activity relationship of mixed anionic/cationic Gemini surfactants[J]. CIESC Journal, DOI: 10.11949/0438-1157.20250682.

图/表 18

图1 几何优化后表面活性剂的离子结构模型及其原子电荷分布（白色、灰色、蓝色、红色、黄色和绿色球体分别代表氢、碳、氮、氧和硫原子，下同）

Fig.1 Ionic structure and atomic charge distribution of surfactants after geometry optimization (white, gray, blue, red, yellow, and green spheres represent hydrogen, carbon, nitrogen, oxygen, sulfur, and corresponding atoms, respectively; same color scheme applies hereinafter)

图2 表面活性剂在气/液界面的“三明治”结构模型（为方便观察，水分子以线条样式表示，下同）

Fig.2 The sandwich mode of surfactants at the air/water interface (for clarity, water molecules are shown as lines; the same applies hereinafter)

表1 不同模拟体系中各表面活性剂的数量

Table 1 The quantity of each surfactant in different simulation systems

模拟体系	AG12-3-12/个	阴离子表面活性剂/个	钠离子/个	氯离子/个	水分子/个
AG12-3-12	28	0	0	56	3000
NaOl	0	56	56	0	3000
SDS	0	56	56	0	3000
SLS	0	56	56	0	3000
AG12-3-12/NaOl复配体系	14	28	28	28	3000
AG12-3-12/SDS复配体系	14	28	28	28	3000
AG12-3-12/SLS复配体系	14	28	28	28	3000

图3 单一及复配表面表面活性剂体系的溶液表面张力与浓度对数图

Fig.3 The plot of solution surface tension versus the logarithm of concentration for single and mixed surfactant systems

表2 单一及复配表面活性剂体系的临界胶束浓度与界面吸附参数

Table 2 CMC and interfacial adsorption parameters of single and mixed surfactant systems

表面活性剂种类	CMC/(mol·L^-1)	界面张力 _CMC /(mN·m^-1)	Γ_max /(mol·m^-2)	A_min /nm²
AG12-3-12	7.93×10^-4	30.56	0.74×10^-6	2.23
NaOl	1.26×10^-3	34.62	1.57×10^-6	1.06
SDS	2.51×10^-3	38.33	1.51×10^-6	1.10
SLS	2.45×10^-3	36.63	1.63×10^-6	1.02
AG12-3-12/NaOl复配体系	3.16×10^-4	25.55	2.77×10^-6	0.60
AG12-3-12/SDS复配体系	4.02×10^-4	23.11	3.06×10^-6	0.54
AG12-3-12/SLS复配体系	4.41×10^-4	20.06	3.13×10^-6	0.53

表3 单一及复配表面活性剂体系的泡沫半衰期

Table 3 Half-life of foam for single and mixed surfactant systems

表面活性剂种类	AG12-3-12	NaOl	SDS	SLS	AG12-3-12/NaOl复配体系	AG12-3-12/SDS复配体系	AG12-3-12/SLS复配体系
泡沫半衰期/s	334	266	285	292	352	366	381

图4 单一及复配表面活性剂体系能量随时间的变化趋势

Fig.4 Time evolution of energy for single and mixed surfactant systems

图5 单一及复配表面活性剂体系在气/液界面的自组装构型

Fig.5 Self-assembly morphology of single and mixed surfactant systems at the air/water interface

图6 单一及复配表面活性剂体系中各组分在气/液界面的浓度分布

Fig.6 Concentration distribution of individual components in single and mixed surfactant systems at the air/water interface

图7 Namine原子分别与Ccarboxyl、Ssulfonic及Ssulfate原子之间的RDF

Fig.7 RDFs for Namine atoms with Ccarboxyl, Ssulfonic, and Ssulfate atoms, respectively

图8 不同阴离子表面活性剂极性基与胺基之间的吸附构型

Fig.8 Adsorption configurations between polar groups of different anionic surfactants and amine groups

图9 不同表面活性剂体系中各表面活性剂分子的θP 和θT 的分布

Fig.9 Distribution of θP and θT of various surfactant molecules in different surfactant systems

图10 极性基与水分子之间的径向分布函数

Fig.10 RDFs between polar groups and water molecules

表4 不同模拟体系的水分子配位数

Table 4 Coordination number of water molecules in different simulation systems

水分子配位数/个	AG12-3-12	AG12-3-12/NaOl复配体系	AG12-3-12/SDS复配体系	AG12-3-12/SLS复配体系
合计	281.92	380.12	384.62	389.10
胺基	281.92	143.14	150.84	146.56
阴离子极性基	—	236.98	233.78	242.54

表5 不同模拟体系中表面活性剂分子及水分子的扩散系数

Table 5 Diffusion coefficients of surfactant molecules and water molecules in different simulation systems

扩散系数/(nm²·ps^-1)	AG12-3-12	AG12-3-12/NaOl复配体系	AG12-3-12/SDS复配体系	AG12-3-12/SLS复配体系
表面活性剂分子	4.67×10^-4	6.83×10^-4	7.67×10^-4	8.33×10^-4
水分子	3.70×10^-3	3.30×10^-3	3.18×10^-3	2.97×10^-3

图11 不同模拟体系中表面活性剂分子及水分子的均方位移

Fig.11 Mean squared displacements of surfactant molecules and water molecules in different simulation systems

表6 不同模拟体系的IFE、Esynergism 及界面厚度

Table 6 IFE， Esynergism and interfacial thickness for different simulation systems

模拟体系	IFE/(kJ·mol^-1)	E_synergism /(kJ·mol^-1)	界面厚度/nm
AG12-3-12/NaOl复配体系	-1221.39	-206.94	0.672
AG12-3-12/SDS复配体系	-1276.06	-264.18	0.730
AG12-3-12/SLS复配体系	-1305.23	-296.53	0.768

图12 泡沫半衰期与不同分子动力学模拟参数的相关性分析

Fig.12 Correlation analysis between half-life of foam and different molecular dynamics simulation parameters

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