Re-entrant Appearance of Phases in a Relaxed Langmuir Monolayer of Tetracosanoic Acid as Determined by X-Ray Scattering
Re-entrant Appearance of Phases in a Relaxed Langmuir Monolayer of Tetracosanoic Acid as Determined by X-Ray Scattering
复制标题
X 射线散射测定二十四烷酸松弛朗缪尔单层中相的重入外观
DOI：
--
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
P. Pershan
中科院分区：
文献类型：
--
作者：
D. K. Schwartz;M. Schlossman;P. Pershan
二十四烷酸的朗缪尔单层的完全弛豫相的结构通过X射线衍射和沿着20.5 °C的等温线的反射来确定。通过允许表面压力在增量压缩之间稳定而获得的等温线被认为与文献中通常看到的恒定速率非松弛等温线有质的不同。在低密度的单层由一个不均匀的膜的岛屿的结晶（或六角）相与分子倾斜排序，这是类似的近晶I液晶。少量的杂质（约0.5%的单分子层）占该区域内表面压力随面积的变化。在压缩到岛之间的自由空间变得可忽略的点时，膜看起来均匀。在进一步压缩时，完全松弛所需的时间变长（即，当分子轴的倾斜角减小时，X射线晶胞被压缩。包括这个…
The structure of the fully relaxed phases of a Langmuir monolayer of tetracosanoic acid is determined by x‐ray diffraction and reflection along an isotherm at ∼20.5 °C. Isotherms taken by allowing the surface pressure to stabilize between incremental compressions are seen to be qualitatively different from the constant‐rate nonrelaxed isotherms typically seen in the literature. At low densities the monolayer consists of an inhomogeneous film of islands of a crystalline (or hexatic) phase with molecular tilt ordering that is analogous to that of the smectic I liquid crystal. Small amounts of impurities (∼0.5% of the monolayer) account for the change in surface pressure with area in this region. Upon compression to the point that the free space between islands becomes negligible the film appears homogeneous. On further compression the time required for full relaxation becomes long (i.e., ∼ hours), the tilt angle of the molecular axis decreases and the x‐ray unit cell is compressed. Including this homogeneou...