中文摘要：

本文通过LB膜仪表面压力-面积（π-A）曲线测量和原子力显微镜（AFM）观测，研究了磷脂酰胆碱（PC）与硬脂酸（SA）二元混合系统在空气／水界面上的物理特性和形态学特征。π-A曲线分析表明，当温度保持在30℃，SA的摩尔分数（XSA）不变时，随着表面压力（π）的增加，二元混合系统的面积（A）不断减小；当表面压力（π）不变时，随着SA的摩尔分数（XSA）的增大，二元混合系统的面积（A）出现非线性周期性减小；表明二元系统从液态扩张相向液态有序相转变。通过吉布斯能量分析，从理论上给出了该系统凝聚程度随π和XSA变化的特征，原子力显微镜观测给出了凝聚程度变化的直观证据，对进一步了解生物膜液晶态的变化具有重要的生物学意义。

英文摘要：

The physical properties and morphology of mixed binary systems of phosphatidylcholine （PC） with stearic acid （SA） have been investigated at the air/water interface by surface pressure-area（π-A） isotherm measurements and by atom force microscopy（AFM） observation. The analyses of the π-A isotherms show that at 30℃ the areas of the binary systems decrease with the increasing surface pressure（π） when the SA molar fraction（ XSA ） keeps invariant, and the areas of the binary systems decrease nonlinearly and periodically with the increasing SA molar fraction when the surface pressure keeps invariant, which indicates that the binary systems have transformed from liquid-expended（LE） phase to liquid-condensed（LC） phase. These results have been proved by Gibbs energy analyses theoretically, and have been directly confirmed by AFM observation. This study has important biological significance for further investigations of the liquid crystal state variations of biomembrane.