【作者】 王攀； 马云云； 孙晓丽； 燕友果； 张军； 刘志斌； 李传勇；

【Author】 Pan Wang;Yunyun Ma;Xiaoli Sun;Youguo Yana;Jun Zhang;Zhibin Liu;Chuanyong Li;College of Science,China University of Petroleum;Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong,China University of Petroleum;

【机构】 中国石油大学(华东)理学院； 新能源物理与材料科学山东省高校重点实验室；

【摘要】 囊泡是表面活性剂在溶液中自组装形成的具有闭合双分子层结构的有序组装体。由于其特殊的结构,在仿生、药物缓释、微反应器及纳米材料制备等领域具有重要的应用。根据Israela提出的聚集理论,具有大极性头基及双柔性尾链结构的表面活性剂可以自组装形成囊泡。由于大部分表面活性剂不具备这样的结构,因此很难自组装形成囊泡。而阴阳离子表面活性剂复配体系,通过阴、阳离子表面活性剂头基之间强烈的静电相互作用使头基结合更加紧密,能够满足表面活性剂自组装形成囊泡的分子结构要求。然而,对于阴阳离子复配体系囊泡微观形成动力学过程认识不足,一定程度上限制了囊泡在实际过程中的应用。因此,本文采用粗粒度分子动力学模拟的方法,研究阴、阳离子表面活性剂复配体系囊泡的形成条件及微观动力学过程。研究发现,阴、阳离子表面活性剂复配比例及尾链链长之比影响聚集形貌,固定复配比例为1:1时,改变阳离子与阴离子的输水尾链的比例分别为16:16,16:12,16:8,聚集形貌依次为蠕虫状胶束,囊泡,片层装胶束;固定阴、阳离子表面活性剂尾链链长分别为12、16,改变复配比例分别为,1:0,3:1,1:1,1:3,及0:1时,聚集形貌依次为球形,片层,囊泡,片层,球形。根据上述研究,结合堆积理论和尾链的体积填补效应可以合理地解释囊泡形成机理。囊泡形成需要经过三个阶段,1成核过程,2胶束融合过程,3自卷曲过程。不同阶段的能量驱动方式不同,成核过程及胶束融合过程主要受尾链疏水作用影响,自卷曲过程主要是熵驱动的结果。本文的研究为筛选囊泡形成条件及发展囊泡形成理论提供一定的借鉴。更多还原

【Abstract】 Vesicles are aggregations with closed bilayer structure which formed by surfactant self-assemblyin solution.Due to the unique assembly structure,vesicles can be exploited in a myriad of applications,such as bionics,drug released,microreactor and nano material spreparation.The surfactant which has big polar head-group and two flexible tail chains can spontaneously form vesicles,according to the theory of "packing Parameter(P)" proposed by Israela.Most of surfactants don’t have such molecular structure,so it’s hard to arrange these surfactants into vesicles.However,vesicle can be formed spontaneously by mixing anion/cation surfactants because two head-groups were closely integrated via the powerful electrostatic attraction.But,insufficient recognition of the mechanism of vesicle formation inherently restricts the potential applications of vesicles.To study the vesicleself-assemble via anion/cation surfactant mixtures,coarse-grained molecular dynamics simulation is employed.The chain length and number ratio of anion/cation surfactants can exhibit complicated surfactant aggregates.When the ratio of anion/cation surfactants was fixed as 1:1,with the change of the ratio of chain length from 16:16 to 16:12 to 16:8,the self-assemble structures appear worm-like micelle,vesicle and lamellarmicelle,respectively.On the other hand,when the carbon numbers of anion/cation surfactants were fixed as16 and 12,with the change of the ratio of anion/cation surfactants from 1:0 to 3:1:to 1:1 to 1:3 to 0:1,the self-assemble structures appear sphere micelle,lamellar micelle,vesicle,lamellar micelle and sphere micelle,respectively.The vesicle formation goes through three stages:nucleating,fusion and curling.The formation of nucleating and fusion is driven by hydrophobic interaction of tail chains,while the formation of curling is entropy driven.These simulation results have lighted new views on the understanding of the formation process of vesicle and the mechanism of vesicle formation of anion/cation surfactant compositions.更多还原