Vollhardt D, Fainerman V B, Liu F
Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam/Golm, Germany.
J Phys Chem B. 2005 Jun 16;109(23):11706-11. doi: 10.1021/jp050796u.
Monolayers of amphiphilic melamine derivatives are good candidates for the formation of supramolecular structures by hydrogen-bonding of nonsurface active species dissolved in the aqueous subphase by molecular recognition. In the present work, the thermodynamic and structural properties of the Langmuir monolayers of a homologous series of a selected amphiphilic melamine-type are characterized. Good candidates for such studies are the decyl, undecyl, and dodecyl homologues of the 2,4-di(n-alkylamino)-6-amino-1,3,5-triazine (2CnH(2n+1)-melamine) monolayers because of their two-phase coexistence region in the accessible temperature range. The characterization of the structural and phase behavior is performed by a combination of surface pressure studies with Brewster angle microscopy (BAM) imaging and Grazing incidence X-ray diffraction (GIXD) measurements. A comprehensive thermodynamic analysis provides good agreement between the experimental surface pressure - area (Pi-A) isotherms and the theoretical curves that were calculated on the basis of equations of state for a large region of monolayer stages developed by us in J. Phys. Chem. 1999, 103, 145. Theoretical curves calculated by application of equations of state only for the fluid monolayer state proposed recently by Rusanov (J. Chem Phys. 2004, 120, 10736) are in good agreement with the experiments in a limited temperature range. A rigorous equation is derived and applied to the experimental results for the calculation of the enthalpy of two-dimensional phase transition. The combination of BAM and GIXD illustrates that the microscopic long range ordering of the condensed monolayer phases is related to the lattice structure of the condensed monolayer.
两亲性三聚氰胺衍生物的单分子层是通过分子识别对溶解在水亚相中无表面活性的物种进行氢键作用来形成超分子结构的良好候选物。在本工作中，对选定的两亲性三聚氰胺型同系物的朗缪尔单分子层的热力学和结构性质进行了表征。2,4-二（正烷基氨基）-6-氨基-1,3,5-三嗪（2CnH(2n+1)-三聚氰胺）单分子层的癸基、十一烷基和十二烷基同系物是此类研究的良好候选物，因为它们在可及温度范围内存在两相共存区域。通过表面压力研究与布鲁斯特角显微镜（BAM）成像以及掠入射X射线衍射（GIXD）测量相结合来表征结构和相行为。全面的热力学分析表明，实验表面压力-面积（π-A）等温线与基于我们在《物理化学杂志》1999年第103卷第145页中提出的用于大面积单分子层阶段的状态方程计算出的理论曲线之间具有良好的一致性。仅应用最近由鲁萨诺夫（《化学物理杂志》2004年第120卷第10736页）提出的用于流体单分子层状态的状态方程计算出的理论曲线在有限温度范围内与实验结果吻合良好。推导了一个严格的方程并将其应用于实验结果以计算二维相变的焓。BAM和GIXD的结合表明，凝聚单分子层相的微观长程有序与凝聚单分子层的晶格结构有关。
