Broniatowski M, Miñones J, Dynarowicz-Łatka P
Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
J Colloid Interface Sci. 2004 Nov 15;279(2):552-8. doi: 10.1016/j.jcis.2004.06.080.
Langmuir monolayers of a homologous series of perfluorododecyl-n-alkanes (general formula F(CF2)12(CH2)nH, abbreviated as F12Hn, where n = 6-20) are investigated through isotherms of surface pressure (pi) and electric surface potential (DeltaV) versus area (A) and quantitative Brewster angle microscopy. The investigated monolayers are found to be liquid in nature. The negative sign of the measured surface potential evidences the orientation of all the investigated molecules with their perfluorinated parts directed toward the air regardless of the length of the hydrogenated unit. Analysis of the direction of the molecular dipole moment with respect to the main axis indicates that the minimum effective dipole moment is achieved for a molecule oriented at an angle of about 35 degrees to the surface normal. The film thickness was evaluated from the relative intensity measurements. The results suggest that the F12Hn molecules are tilted to the interface in the vicinity of collapse, which is in accordance with the liquid character of their monolayers.
通过表面压力（π）和表面电势（ΔV）对面积（A）的等温线以及定量布鲁斯特角显微镜研究了全氟十二烷基正构烷烃同系物（通式为F(CF₂)₁₂(CH₂)ₙH，缩写为F₁₂Hₙ，其中n = 6 - 20）的朗缪尔单分子层。研究发现所研究的单分子层本质上是液态的。所测表面电势的负号表明，无论氢化单元的长度如何，所有被研究分子的全氟部分都指向空气。对分子偶极矩相对于主轴方向的分析表明，对于与表面法线成约35度角取向的分子，有效偶极矩最小。通过相对强度测量评估了膜厚度。结果表明，F₁₂Hₙ分子在接近崩塌时向界面倾斜，这与其单分子层的液态性质相符。
