CRYSTAL STRUCTURAL CONTROL OF ULTRA-THIN ORGANIC FILMS BY MIXING LB TECHNIQUE INTRODUCING SPACER MOLECULES

通过在花生酸（C20） LB膜中引入吡咯或富勒烯（C60）分子等“间隔分子”来控制langumur - blodgett （LB）膜中分子的横向间距。以吡咯（py）或C60为客体分子，研究了C20 LB膜的分子排列随着吡咯（py）量或C60量的增加而改变。采用压力-面积曲线、石英晶体微天平法和原子力显微镜（AFM）对C20 LB薄膜的分子占据面积变化进行了分析。研究发现，C20 LB膜可以包含比C20大1.5倍的分子。原子力显微镜观察表明，加入间隔分子后，C20的占据面积增大，但C20分子保持高度有序的分子排列。原子力显微镜观察到的晶体结构变化与基于分子力学的计算机模拟结果吻合较好。实验和计算机模拟结果表明，C20 LB膜的晶格常数易于通过LB膜中间隔分子的数量来控制。利用这些特性，制备了几种由C20和C60组成的混合LB膜，并用石英晶体微天平研究了这些膜对气体分子的吸附特性。气体吸附量与层数的关系表明，随着LB膜分子间距的增加，气体分子进入LB膜的渗透率显著增加。采用含C60的LB膜对不同大小和结构的气体分子进行了筛选。含C60 LB膜的这一特性可应用于具有分子筛分功能的新型气体传感器。

Lateral spacing of the molecules in the Langumuir-Blodgett (LB) films were controlled by introducing "Spacer Molecules" such as pyrrole or fullerene (C60) molecules into arachidic acid (C20) LB films. The transformation of the molecular arrangement of C20 LB film was studied with an increase of pyrrole (py) quantity or C60 quantity which we used as guest molecules to the host molecules, C20. The change of molecular occupation area of a C20 LB films was estimated by pressure-area curves, quartz crystal microbalance method and atomic force microscopy (AFM). It was found that that a C20 LB film can contain 1.5 times as large as C20 molecules. The observation by AFM showed that the enlargement of the occupation area of C20 upon addition of spacer molecules, however, the molecules of C20 maintained the highly ordered molecular arrangement. The change of the crystal structure observed by AFM agreed well with the results of computer simulation based on molecular mechanics. The experimental and computer simulation results showed that the lattice constant of a C20 LB film is easy to control by the quantity of spacer molecules contained in the LB film.Using these characteristics, several kinds of mixed LB films, composed of C20 and C60, were prepared and the adsorption characteristics of gas molecules to these films were studied using a quartz crystal microbalance. The dependence of the amount of the gas adsorbed on the number of layers reveal that the permeability of the gas molecules into the LB films remarkably increase with an increase of the intermolecular spacing of LB films. Gas molecules with different sizes or structure were sifted by using C60 containing LB films. This characteristic of the LB films containing C60 can be applied to a novel gas sensor with a molecular sifter function.