Structure and thermal behavior of a layered silver hydroxyalkanecarboxylate.
The structure and thermal behavior of silver 16-hydroxyhexadecanoate (Ag-HHDA) have been investigated by using various analytical tools. The X-ray diffraction pattern was composed of a series of peaks that could be indexed to (0k0) reflections of a layered structure. Diffuse reflectance infrared Fourier transform spectroscopy revealed that the alkyl chains in Ag-HHDA as prepared were in an all-trans conformational state. Upon heating the sample, noticeable structural changes took place particularly in two temperature regions. The first structural change occurring at approximately 380 K was a partially irreversible one in which the binding state of carboxylate to silver converted from bridging into unidentate. A second dramatic structural change occurring at approximately 480 K was a totally irreversible process that could be associated with the decomposition of Ag-HHDA. All of these thermal characteristics of Ag-HHDA are comparable to those of silver stearate (Ag-STA). Separately, we have endeavored without success to intercalate polar molecules into the OH-group terminated layers in Ag-HHDA; the exfoliation of Ag-HHDA in various polar solvents was also unsuccessful. This is indicative of the presence of a rather stronger H-bond in Ag-HHDA, but the comparable thermal characteristics of Ag-HHDA and Ag-STA dictate that the thermal behavior of silver alkanoate is determined exclusively by the silver-to-carboxylate group interaction. This is in sharp contrast to the case of two-dimensional self-assembled monolayers for which the terminal functionalities play a crucial role in determining the structure and thermal stability of entire monolayers.
Choi
Hyouk Jin
HJ
Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, South Korea.
Han
Sang Woo
SW
Lee
Seung Joon
SJ
Kim
Kwan
K