摘要
采用耗散分子动力学模拟方法,研究了氨基修饰的表面活性剂聚二甲基硅氧烷与羧基修饰的二氧化硅纳米颗粒在硅油-水界面上的自组装行为,通过分析油-水界面性质(界面厚度和界面张力)和活性剂的结构性质(回转半径),探讨了活性剂质量分数ω_(S)和纳米颗粒质量分数ω_(N)等对界面性质的影响,阐明了自组装过程中界面性质的影响因素。结果表明,纳米颗粒和表面活性剂在油-水界面上自发组装成纳米颗粒表面活性剂,当ω_(S)=0.005~0.2时,纳米颗粒表面活性剂可有效降低界面张力;而在ω_(S)=0.2~0.5时,该组装行为使界面张力随ω_(S)而提高。当ω_(S)=0.2时,活性剂的回转半径最大、随时间波动最小,表明活性剂分子被拉伸效果更明显,此时体系的界面张力最低。活性剂结构对界面张力影响较大,活性剂链长在8~17时,端氨基占比较大,即链长最短时,体系的界面张力最低,界面厚度最大。当纳米颗粒直径在2.44~12.21Å(1Å=0.1nm)时,界面张力随颗粒直径增大而降低;当ω_(N)=0.0165625~0.1325时,界面张力随ω_(N)而提高。当活性剂与颗粒的作用参数在9~21时,作用参数对界面性质无影响。
This study used the dissipative molecular dynamics simulation method(DPD)to study the selfassembly behaviors of the amino-modified polymer surfactant polyimethylsiloxane and the carboxymodified silica nanoparticle on a silicone oil-water interface,and explored the internal mechanisms in self-assembly behaviors for a wide range of surfactant mass fraction.The effects of surfactant and nanoparticle mass fractions(ω_(S),ω_(N))were investigated by examining the interface properties(interface thickness and interface tension)and structural properties(rotation radius).The results showed that nanoparticles and surfactants spontaneously assembled into nanoparticle surfactants at the oil-water interface.When ω_(S)=0.005—0.2,it can effectively reduce the interfacial tension.While ω_(S)=0.2—0.5,this assembly behavior caused the interfacial tension to increase with increasing ω_(S).For ω_(S) of 0.2,the radius of gyration of surfactant was the largest and the fluctuation with time was the smallest,and the interfacial tension of the system was the lowest,indicating that the stretching effect of surfactant molecules was more obvious.The interface tension increased with increasing surfactant chain,showing that the proportion of end amino groups in surfactants played a dominant action on interface behaviors.For the surfactant chain of 8,the feature of the lowest interfacial tension and the largest thickness was highlighted.The interfacial tension decreased as the nanoparticle diameter increased from 2.44Å to 12.21Å,and increased as ω_(N) raised from 0.0165625 to 0.1325.When the interaction parameter between the surfactant and nanoparticle was raised from 9 to 21,the variation in interaction parameter had no influence on the interface properties.
作者
宋超
叶学民
李春曦
SONG Chao;YE Xuemin;LI Chunxi(Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology,North China Electric Power University,Baoding 071003,Hebei,China)
出处
《化工进展》
EI
CAS
CSCD
北大核心
2022年第S01期366-375,共10页
Chemical Industry and Engineering Progress
关键词
自组装
分子模拟
界面张力
表面活性剂
纳米粒子
聚合物
self-assembly
molecular simulation
interfacial tension
surfactants
nanoparticles
polymers