Supramolecular Assembly and Headgroup Effect in Interfacial Organized Films (I): A Study of Some Bolaamphiphiles

Abstract

Two bola form Schiff bases derivatives with different substituted head groups have been designed and their interfacial phase behaviors and coordination with Cu(II) ions were investigated. It has been found that while one molecule with benzene headgroup formed dotted aggregations at the air/water interface, another with naphthyl moiety as head group formed crystalline multilayer films on water surface. When on the sub phase containing Cu(II) ions, both of the Schiff bases can coordinate with Cu(II) in situ in the spreading films with the obvious conformational change of alkyl chains. The in situ Cu(II)-coordinated films could be transferred onto solid substrates and subsequently characterized by various spectroscopic methods such as UV-vis and Fourier transform infrared spectra as well as the morphological character with atomic force microscopy measurement. In comparison, the ex situ coordination process at the liquid/solid interface have also been investigated by continuous spectral measurement. Depending on the different head groups, these amphiphiles showed different aggregation behaviors in the Langmuir-Blodgett films. Particularly, during the coordination process of ligand with Cu(II) ions in organized molecular films, great conformational change of the alkyl chains was observed. At the same time, a rational explanation about the head group effect on regulating the aggregation behaviors was discussed.

Keywords:

• Bolaamphiphile
• headgroup effect
• Langmuir-Blodgett films
• supramolecular assembly

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (20903078), the Natural Science Foundation of Hebei Province (B2009000347), the Support Program for Hundred Excellent Innovation Talents from Universities and Colleges of Hebei Province (CPRC020), the Scientific Research Plan of the Education Department of Hebei Province (Z2009146), and the Doctoral Foundation of Yanshan University (B360). Additional thanks are due to Dr. Chao Yan for his help in the measuring procedure of reflection absorption FTIR spectra.