動態接觸角分析法在Langmuir-Blodgett分子膜表面性質的鑑定

陳祉雲 ； 陳亮惠 ； 李玉郎 ； 沈育仁 ； 楊曉菁

《化工》 48卷5期 (2001/10) Pp. 1-15

https://doi.org/10.29803/CE.200110.0001

摘要

本文探討DPPC、DMPC、膽固醇、硬脂胺及硬脂酸等五種物質在純水表面的單分子膜行為及一分子層LB膜的潤濕性，並與直接塗佈法及溶液沈浸法所得的結果相比較。實驗結果發現在純水表面DPPC、DMPC及膽固醇三者單分子膜都有很好的穩定性，其次為硬脂胺，而硬脂酸的單分子膜則極不穩定。這些單分子膜在π=25mN/m的膜壓下轉移至親水性的玻璃面所得的LB膜，在巨觀的潤濕性上都很均勻。DPPC及DMPC LB 膜表面的接觸角相近，但與直接塗佈法所得連續膜的接觸角相比，LB膜的後退接觸角明顯較陷，顯示表面可能有祼露的玻璃面；上述的現象在膽固醇及硬酯酸LB膜的表面亦有相似的情形發現，尤其在膽固醇LB膜上，其與水之間的接觸角與沈積前的玻璃面相近，表示此膜在接觸角的測定過程中有嚴重的水分滲透現象。在不同的製備程序中都發現，硬酯胺的─NH2根對玻璃表面有較強的親和力，因此在五種測定物質中，硬酯酸薄膜的疏水性是最大的；在硬酯胺LB膜表面的接觸角更可達到甲基根(-CH3)的理論疏水性，足見硬酯胺分子在LB膜表面有緊密且規則排列的特性。對不同製備程序的比較發現，LB膜沉積法可得到較為均勻的薄膜。LB膜表面分子排列的規則性除了與其在液面上的單分子膜特性有關外，亦受到轉移過程中分子與基板間的作用力所控制。

並列摘要

The behavior of monolayers of DPPC, DMPC, cholesterol, stearic amine, and stearic acid on pure water were investigated. The monolayers were transferred to hydrophilic glass surfaces to prepare Langmuir-Blodgettfilms of one molecular layer. The wettability of the LB films were analyzed by dynamic contact angle measurements and were compared with the results on films prepared by methods of solution dipping and spreading coating. The experimental results show that the mono-layers of DPPC, DMPC, and Cholesterol were very stable on subphase of pure water and the stearic acid has least stability. The wettalility of LB films prepared at π= 25 mN/m were uniform in general. The values of contact angles for LB films of DPPC and DMPC were similar. However, the receding contact angle of the two compounds is quite smaller than the value of a continuous film prepared by spreading coating, which reveals that the LB film is not closely packed but with exposure of glass substrate. This phenomenon is also found on LB of cholesterol and stearic acid. Especially on the cholesterol LB film, the contact angles are similar to those of a clean glass surface. The-NH2 group of the stearic amine is found to have higher affinity with the glass, so the stearic amine film has highest hydro-phobic property among the five compounds. The contact angle of water on LB film of stearic amine is close to that of a methyl-terminated surface, which reveals the closely packed and regular structure. The wettability of LB film is more uniform compared with film prepared by the other methods. It is also found that the organization of the molecules on the LB films is related not only by the behavior of monolayer on the subphase but by the interaction between the transferred molecule and the substrate.