Synthesis and Surface Properties of New Ureas and Amides at Different Interfaces
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- 作者：Katharina Dreger ; Bo Zou ; Zhongcheng Mu ; Hans Joachim Galla ; Lifeng Chi ; Harald Fuchs ; and Hans J. Schä ; fer
- 刊名：Langmuir
- 出版年：2006
- 出版时间：February 14, 2006
- 年：2006
- 卷：22
- 期：4
- 页码：1619 - 1625
- 全文大小：243K
- 年卷期：v.22,no.4(February 14, 2006)
- ISSN：1520-5827
文摘
The influence of the urea and amide group in the alkyl chain of methyl nonadecanoate on the surface propertiesis investigated and compared. For that purpose, the ureas CH3O2C-(CH2)m-NHCONH-(CH2)n-CH3 (n + m = 14)[1 (m = 2), 3 (m = 3), and 5 (m = 4)] and the amides CH3O2C-(CH2)m-NHCO-(CH2)n-CH3 (n + m = 15) [2(m = 2), 4 (m = 3), and 6 (m = 4)] were synthesized. The 
/A isotherms of the ureas show up to the attainabletemperature of 313 K no LE phase, which indicates a very stable LC phase. The amides exhibit a two phase plateauregion, with the exception of 2. The different behavior is connected with the hydrogen bond energies, which arestronger with the ureas in the LC than in the LE phase, whereas those of the amides have a similar strength in bothphases. The effect of hydrogen bonds in self-assembled molecules of N,N'-dialkylurea CH3-(CH2)m-NHCONH-(CH2)n-CH3 (m + n = 14) [7 (n = 2)] was visualized by STM at the octylbenzene/graphite interface. Compound7 forms a lamella structure with a periodicity of one molecule length. The tilt angle of 86
± 2 to the edge of thelamella points to a nearly orthogonal arrangement of the molecules. It indicates two equivalent bonds between theaza-hydrogens and the carbonyl oxygen. A similar arrangement is proposed for the LC phase of the ureas at theair/water interface.
/A isotherms of the ureas show up to the attainabletemperature of 313 K no LE phase, which indicates a very stable LC phase. The amides exhibit a two phase plateauregion, with the exception of 2. The different behavior is connected with the hydrogen bond energies, which arestronger with the ureas in the LC than in the LE phase, whereas those of the amides have a similar strength in bothphases. The effect of hydrogen bonds in self-assembled molecules of N,N'-dialkylurea CH3-(CH2)m-NHCONH-(CH2)n-CH3 (m + n = 14) [7 (n = 2)] was visualized by STM at the octylbenzene/graphite interface. Compound7 forms a lamella structure with a periodicity of one molecule length. The tilt angle of 86 ± 2 to the edge of thelamella points to a nearly orthogonal arrangement of the molecules. It indicates two equivalent bonds between theaza-hydrogens and the carbonyl oxygen. A similar arrangement is proposed for the LC phase of the ureas at theair/water interface.