Xu Chaohang, Bi Ran, Wang Sijing, Tang Xiaojun, Zhu Xiaolong, Li Guochun
School of Safety Science and Emergency Management, Wuhan University of Technology, Wuhan 430070, China.
School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China.
Polymers (Basel). 2025 Aug 30;17(17):2361. doi: 10.3390/polym17172361.
Water-soluble polymers are often used as additives to adjust the foam properties of surfactant. In this study, the effects of water-soluble polymer poly(ethylene oxide) (PEO) on foam properties of two anionic surfactants, i.e., ammonium lauryl ether sulfate (ALES) and sodium dodecyl sulfate (SDS), were investigated by experimental and molecular dynamics simulation methods. Experimental results show that the addition of PEO can reduce the foaming ability of the two surfactants, but the inhibitory effect of PEO on the foaming ability is weakened at high surfactant concentration. Compared with ALES, PEO has a more significant inhibitory effect on the foaming ability of SDS. With the increase in PEO concentration, the half-life time of foam drainage in surfactant/water-soluble polymer composite systems gradually increases. The synergistic effect between PEO and ALES is stronger than that between PEO and SDS, resulting in a longer half-life time of foam drainage in ALES/PEO composite system. Molecular dynamics simulation results indicate that the addition of PEO can decline the air-water interface thickness of bubble films and the tail tilt angle of surfactant molecules at the air-water interface. The reduction in tail tilt angle means that the surfactant molecules are more vertical to the air-water interface and the hydrophobic interaction between adjacent tail chains of surfactants is weakened, which is unfavorable to the formation of bubble films, thus decreasing the foaming ability of surfactants. Because the ALES/PEO system has larger air-water interface thickness and surfactant tail tilt angle than the SDS/PEO system, the inhibitory effect of PEO on the foaming ability of ALES is weaker than that of SDS. Adding PEO can lower the peak position of the first hydration layer of surfactant head groups, increase the number of hydrogen bonds, and reduce the diffusion coefficient of water molecules, so that the surfactant/water-soluble polymer system has longer half-life time of foam drainage than the pure surfactant system. Due to the synergistic effect between ALES and PEO, the ALES/PEO system has a higher peak value of the first hydration layer of surfactant head groups, more hydrogen bonds, and lower diffusion coefficient of water molecules than the SDS/PEO system. Therefore, the half-life time of foam drainage in the ALES/PEO system is longer than that in the SDS/PEO system.
水溶性聚合物常被用作添加剂来调节表面活性剂的泡沫性质。在本研究中，通过实验和分子动力学模拟方法，研究了水溶性聚合物聚环氧乙烷（PEO）对两种阴离子表面活性剂，即月桂醇聚醚硫酸铵（ALES）和十二烷基硫酸钠（SDS）泡沫性质的影响。实验结果表明，添加PEO会降低两种表面活性剂的发泡能力，但在高表面活性剂浓度下，PEO对发泡能力的抑制作用会减弱。与ALES相比，PEO对SDS发泡能力的抑制作用更显著。随着PEO浓度的增加，表面活性剂/水溶性聚合物复合体系中泡沫排液的半衰期逐渐延长。PEO与ALES之间的协同作用强于PEO与SDS之间的协同作用，导致ALES/PEO复合体系中泡沫排液的半衰期更长。分子动力学模拟结果表明，添加PEO会降低气泡膜的气-水界面厚度以及表面活性剂分子在气-水界面处的尾链倾斜角。尾链倾斜角的减小意味着表面活性剂分子更垂直于气-水界面，相邻表面活性剂尾链之间的疏水相互作用减弱，这不利于气泡膜的形成，从而降低了表面活性剂的发泡能力。由于ALES/PEO体系的气-水界面厚度和表面活性剂尾链倾斜角比SDS/PEO体系大，PEO对ALES发泡能力的抑制作用比SDS弱。添加PEO可以降低表面活性剂头基第一水化层的峰值位置，增加氢键数量，并降低水分子的扩散系数，从而使表面活性剂/水溶性聚合物体系的泡沫排液半衰期比纯表面活性剂体系更长。由于ALES与PEO之间的协同作用，ALES/PEO体系中表面活性剂头基第一水化层的峰值更高，氢键更多，水分子扩散系数更低。因此，ALES/PEO体系中泡沫排液的半衰期比SDS/PEO体系更长。
