• Rigid Urea and Self-Healing Thiourea Ethanolamine Monolayers
    C. Stefaniu, P.-L. Zaffalon, A. Carmine, Q. Verolet, S. Fernandez, T.A. Wesolowski, G. Brezesinski and A. Zumbuehl
    Langmuir, 31 (4) (2015), p1296-1302
    DOI:10.1021/la5039987 | unige:55058 | Abstract | Article HTML | Article PDF | Supporting Info
 
A series of long-tail alkyl ethanolamine analogs containing amide-, urea-, and thiourea moieties was synthesized and the behavior of the corresponding monolayers was assessed on the Langmuir–Pockels trough combined with grazing incidence X-ray diffraction experiments and complemented by computer simulations. All compounds form stable monolayers at the soft air/water interface. The phase behavior is dominated by strong intermolecular headgroup hydrogen bond networks. While the amide analog forms well-defined monolayer structures, the stronger hydrogen bonds in the urea analogs lead to the formation of small three-dimensional crystallites already during spreading due to concentration fluctuations. The hydrogen bonds in the thiourea case form a two-dimensional network, which ruptures temporarily during compression and is recovered in a self-healing process, while in the urea clusters the hydrogen bonds form a more planar framework with gliding planes keeping the structure intact during compression. Because the thiourea analogs are able to self-heal after rupture, such compounds could have interesting properties as tight, ordered, and self-healing monolayers.

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