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Issue 1, 2006
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Conformational and thermal behavior of a pH-sensitive bolaform hydrogelator

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Abstract

The phase behavior of the symmetric long-chain bolaamphiphile dotriacontan-1,1′-diyl-bis[2-(dimethylammonio)ethyl phosphate] (Me2PE-C32-Me2PE) was investigated in aqueous suspensions of different pH by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). At pH 5 the compound exhibits excellent properties as a hydrogelator by forming a dense network of helically structured nanofibrils with a diameter of 3–4 nm. The phase behavior of Me2PE-C32-Me2PE is compared with the previously examined trimethylammonio analogue PC-C32-PC, whose self-assembly process seems to be exclusively driven by hydrophobic interactions. At pH 5, Me2PE-C32-Me2PE can form intermolecular hydrogen bonds between the headgroups, which causes a significantly higher stability of the nanofibrils up to at least 75 °C. In contrast, no pronounced gelling properties are observed at pH 10. Obviously, the negatively charged headgroups seem to prevent the suspension from gelling. Nevertheless, nanofibrils are formed, but at 75 °C a fragmentation into smaller aggregates occurs due to the lack of stabilizing effect of intermolecular hydrogen bonds and the destabilizing effect of the negatively charged headgroups.

Graphical abstract: Conformational and thermal behavior of a pH-sensitive bolaform hydrogelator

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Publication details

The article was received on 05 Oct 2005, accepted on 14 Nov 2005 and first published on 29 Nov 2005


Article type: Paper
DOI: 10.1039/B514163J
Citation: Soft Matter, 2006,2, 77-86
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    Conformational and thermal behavior of a pH-sensitive bolaform hydrogelator

    K. Köhler, A. Meister, G. Förster, B. Dobner, S. Drescher, F. Ziethe, W. Richter, F. Steiniger, M. Drechsler, G. Hause and A. Blume, Soft Matter, 2006, 2, 77
    DOI: 10.1039/B514163J

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