Structure-property relationship in stimulus-responsive bolaamphiphile hydrogels |
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Authors: | Meister Annette Bastrop Martin Koschoreck Sven Garamus Vasil M Sinemus Thomas Hempel Günter Drescher Simon Dobner Bodo Richtering Walter Huber Klaus Blume Alfred |
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Institution: | Institute of Chemistry, MLU Halle-Wittenberg, Mühlpforte 1, 06108 Halle, Germany. annette.meister@chemie.uni-halle.de |
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Abstract: | The formation of temperature-, concentration-, and pH-responsive hydrogels composed of the symmetric long-chain bolaamphiphile dotriacontane-1,1'-diyl bis2-(dimethylammonio)ethyl]phosphate] (Me(2)PE-C32-Me(2)PE) was investigated by rheological, scattering, and spectroscopic techniques. At pH 5, this bolaamphiphile is known to form a dense network of helically structured nanofibers (K?hler et al. Soft Matter 2006, 2, 77-86). Rheological measurements and dynamic light scattering were used to describe the macroscopic behavior of the hydrogels. Small-angle neutron scattering (SANS) and time-resolved static light scattering were applied to get information about the morphology of the self-assembled aggregates. Finally, solid-state 31P NMR spectroscopy was used to gain insight into the mobility of the bolaamphiphile molecules within the fiber aggregates. In comparison with the previously examined trimethylammonio analogue PC-C32-PC, which forms temperature-dependent hydrogels, Me(2)PE-C32-Me(2)PE exhibits additional concentration- and pH-dependent gelling properties. The significantly higher stability of the Me(2)PE-C32-Me(2)PE hydrogel is supported by the SANS data, which indicate the presence of fiber aggregates up to 50 degrees C. |
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