摘要
应用Langmuir天平、LB技术、原子力显微镜(AFM)与摩擦力显微镜(FFM)研究不同类型的表面活性剂混合不溶膜的性质。提供它们的表面压-面积(π-A)曲线和单分子层图象。结果表明C18H37SO3Na-C8F17COOH混合凝聚膜发生相分离,C18H37SO3Na形成六方微畴分布在连续的C8F17COOH相中;C12H25SO4Na-C18H37N(CH3)3Br形成了相当均匀完整的混合膜;C18H37N(CH3)3Br-C8F17COOH所成膜呈微不均匀状态。从热力学和分子动力学角度进一步研究了C18H37SO3Na-C8F17COOH混合凝聚膜体系的分子间相互作用特性。结果表明,碳氢链与碳氟链之间的VanderWaals相互作用弱于两碳氟链之间的或两碳氢链之间的相互作用。这是碳氟链与碳氢链化合物互疏作用的根源。但是由此产生的能量差别不大,故如果两分子的其他基团间存在其他相互作用则这种互疏性将被掩盖而难以察觉。这正是造成在不同的碳氟链表面活性剂与碳氢链表面活性剂混合研究中有时得到混合胶团,又有时得到两种胶团的原因。
In the present work,various mixed monolayers of fluocarbon and hydrocarbon surfactants,including C 18 H 37 SO 3Na C 8F 17 COOH,C 12 H 25 SO 4Na C 18 H 37 N(CH 3)Br C 8F 17 COOH mixtures were investigated by AFM and LB technique.π A curves and topographic images of monolayers were provided.It is shown that C 18 H 37 SO 3Na forms hexangonal domains dispersing in the continuous two dimensional phase of C 8F 17 COOH,showing two dimensional phase separation and crystallization.Things are different in the other two systems:C 12 H 25 SO 4Na C 18 H 37 N(CH 3) 3Br mixture forms a homogeneous mixed monolayer,while the mixed monolayer of C 18 H 37 N(CH 3) 3Br and C 8F 17 COOH mixture shows homogeneous in macroscope but heterogeneous in microscope.Further studies from the view points of thermodynamics and molecular dynamics were conducted.Explanation and mechanism for the observations are suggested.Anyway,there will be an increase of energy when fluorocarbon chain contacted with a hydrocarbon chain,therefore separation of FC and HC groups in a suitable degree of without influence on the coulumbic interaction between their hydrophilic groups will occur spontaneously.Such a mechanism must result in the microheterogenity in the mixed monolayer.
出处
《日用化学工业》
CAS
CSCD
北大核心
1999年第1期1-6,共6页
China Surfactant Detergent & Cosmetics
关键词
碳氟链
表面活性剂
碳氢链
混合
分子层结构
fluorocarbon and hydrocarbon surfactant,mixed monolayer,two dimensional phase separation and crystallization,mutual phobicity between FC and HC surfactant