Broniatowski Marcin, Dynarowicz-Łatka Patrycja
Department of General Chemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
J Colloid Interface Sci. 2006 Sep 1;301(1):315-22. doi: 10.1016/j.jcis.2006.05.007. Epub 2006 May 5.
A series of semifluorinated alcohols differing in the proportion of the perfluorinated to hydrogenated chains length was synthesized and investigated in Langmuir monolayers using surface pressure and surface potential measurements. All the investigated semifluorinated alcohols were found to be capable of stable floating monolayer formation. The stability of monolayers was found to be higher upon increasing the length of the perfluorinated segment. A lower stability of the monolayers from alcohols having shorter perfluorinated fragment was attributed to the aggregation process, which was visualized with Brewster angle microscopy (BAM). Most condensed monolayers were formed by compounds with longer perfluorinated moiety, whereas monolayers composed by molecules with an iso-branched perfluorinated segment were found to be more expanded. The change of electric surface potential was negative along the whole compression. The maximum absolute values of DeltaV varies, depending on the number of CF(2) groups, from ca. -400 mV for F6H10OH to ca. -700 mV for F10H10OH. The dipole moments of free molecules were calculated with Hyperchem, and the obtained values were approximately the same (within the experimental error), i.e., 2.8D for all the investigated molecules, independently on the perfluorinated fragment length. The dipole moment vector was found to be virtually aligned to the main molecular axis for the studied compounds. Therefore, the observed differences in the measured values of DeltaV can result from a different dielectric permittivity of a particular monolayer.
合成了一系列全氟链与氢化链长度比例不同的半氟化醇，并使用表面压力和表面电位测量在朗缪尔单分子层中对其进行了研究。发现所有研究的半氟化醇都能够形成稳定的漂浮单分子层。发现随着全氟链段长度的增加，单分子层的稳定性更高。具有较短全氟链段的醇形成的单分子层稳定性较低，这归因于聚集过程，该过程通过布鲁斯特角显微镜（BAM）得以观察。大多数凝聚的单分子层由具有较长全氟部分的化合物形成，而由具有异支链全氟链段的分子组成的单分子层则更具扩展性。在整个压缩过程中，表面电势的变化为负。ΔV的最大绝对值因CF(2)基团的数量而异，从F6H10OH的约-400 mV到F10H10OH的约-700 mV。使用Hyperchem计算了游离分子的偶极矩，得到的值大致相同（在实验误差范围内），即所有研究分子的偶极矩均为2.8D，与全氟链段长度无关。发现对于所研究的化合物，偶极矩矢量实际上与分子主轴线对齐。因此，观察到的ΔV测量值的差异可能是由于特定单分子层的介电常数不同所致。
