title: Structure-property relationship in stimulus-responsive bolaamphiphile hydrogels.
abstract: The formation of temperature-, concentration-, and pH-responsive hydrogels composed of the symmetric long-chain bolaamphiphile dotriacontane-1,1'-diyl bis[[2-(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 (Köhler 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.
authors.affiliation: Institute of Chemistry, MLU Halle-Wittenberg, Mühlpforte 1, 06108 Halle, Germany. annette.meister@chemie.uni-halle.de
authors.forename: Annette
authors.initials: A
authors.lastname: Meister
authors.forename: Martin
authors.initials: M
authors.lastname: Bastrop
authors.forename: Sven
authors.initials: S
authors.lastname: Koschoreck
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Thomas
authors.initials: T
authors.lastname: Sinemus
authors.forename: Günter
authors.initials: G
authors.lastname: Hempel
authors.forename: Simon
authors.initials: S
authors.lastname: Drescher
authors.forename: Bodo
authors.initials: B
authors.lastname: Dobner
authors.forename: Walter
authors.initials: W
authors.lastname: Richtering
authors.forename: Klaus
authors.initials: K
authors.lastname: Huber
authors.forename: Alfred
authors.initials: A
authors.lastname: Blume
mesh_terms: D000473:Alkanes; D003931:Diacetyl / Q000031:analogs & derivatives*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008744:Methylamines / Q000737:chemistry; D009502:Neutrons; D012212:Rheology; D053838:Scattering, Small Angle; D013696:Temperature
chemical_list: D000473:Alkanes; D020100:Hydrogels; D008744:Methylamines; C578748:dotriacontane; D003931:Diacetyl; C023336:trimethylamine