Study on the Molecular Motion in Organic Thin Film using Spin Probe Method and Molecular Dynamics

(1)。用自旋探针法研究了两亲分子在LB膜中的取向和分子运动。在不同温度下，测量了5-，10-和16-十二烷基硬脂酸(DXSTAs)及其与硬脂酸(STA)与聚烯丙基胺(STA)的混合物在不同温度下的电子自旋共振光谱，从可以忽略分子运动的液氮温度的角度依赖关系，确定了准确的分子取向及其分布。从温度依赖关系来看，亚甲基链的末端发生了分子运动，而取向规律性保持不变。用自旋探针法研究两亲分子在流延膜中的取向和分子运动。从角度变化可以得到…此外，ESR谱的温度依赖性表明，各向同性运动是通过亚甲基链的尾部进行的，而亚甲基链的运动保持在头基附近的取向。含探针分子的混合LB膜相分离条件的控制研究发现，在含有硬脂酸和全氟辛酸的混合LB膜中，当多羟基单元的位置离头基团较近时，不会发生相分离。由于探针分子在水表面单分子膜中的分子占位面积随着探针位置向亲水基团的靠近而增大，这表明探针分子间的面内内聚力的降低是导致该探针分子具有相分离特性的主要原因。用分子动力学方法模拟有机薄膜中的分子运动用分子动力学方法编制的这种体系的计算程序已经达到了几乎可以用于实际研究的水平。结果表明，从含有自旋探针分子的LB膜的ESR谱及其分析可望获得这些有机薄膜中分子运动的详细信息。较少

(1). Elucidation of orientation and molecular motion of amphiphilic molecules in LB films by spin probe method.Electron spin resonance spectra for the Langmuir-Blodgett (LB) films of 5-, 10-, and 16-doxylstearic acids (DXSTAs) and their mixtures with stearic acid (STA) complexed with polyallyl-amine were measured at various angles between the applied magnetic field and the film normal at various temperatures, From the angle dependence at the liquid nitrogen temperature where molecular motion can be neglected, accurate molecular orientation and its distribution were determined. From the temperature dependence, it was shown that end part of methylene chain did molecular motion, while the orientation regularity is kept in these LB films.(2). Elucidation of orientation and molecular motion of amphiphilic molecules in cast films by spin probe method.The spin probe method was applied to cast films of the tetraalkylammonium chloride with two long methylene chains. From the angular variation a … More nd the temperature dependence of the ESR spectra, it was shown that the isotropic motion was carried out by the tail part of methylene chain, while the motion of the methylene chain kept the orientation in the vicinity of the headgroup in these cast films.(3). Control of phase separation condition of mixed LB films containing probe molecules.It was found that in mixed LB films containing doxylstearic acid and perfluorodecanoic acid phase separation did not occur when the position of doxyl unit is closer to head group. Since the molecular occupation area of the probe molecule in monomolecular film on water surface increases due to the steric hinderance as the probe position approaches to the hydrophilic group, it was suggested that that decrease in the in-plane cohesion force between probe molecules was a main cause for the phase separation characteristics of such probe molecule.(4). Simulation of the molecular motion in organic thin films using molecular dynamics methodThe calculation program of such system by the molecular dynamics method which had advanced the improvement until now reached the level which can be almost used for actual research. As the result, it is expected that detailed information can be obtained on the molecular motion in these organic thin films from the ESR spectra of LB films containing spin probe molecules and their analysis with this program. Less