TY - JOUR
T1 - Dynamic evolving two-component supramolecular gels -hierarchical control over component selection in complex mixtures
AU - Edwards, W.
AU - Smith, D.K.
PY - 2013/4/17
Y1 - 2013/4/17
N2 - We report a two-component acid-amine gelation system which forms instant organogels on simple mixing. We investigate self-assembly using a wide range of different amines and identify the optimum amines for gelation to occur. Using NMR and other spectroscopic methods, we unambiguously determine the stoichiometry of the complex responsible for gelation (1:1) and characterize the noncovalent interactions responsible for gelation. Using Kamlet-Taft parameters we gain a detailed understanding of the role of solvent on gelation. Most importantly, we explore the ability of these multicomponent systems to assemble from complex mixtures, and using NMR can determine which components are preferentially taken up into the immobile "solid-like" fiber network and which components remain mobile in the "liquid-like" solvent phase. In this way, we determine that the component selection process is controlled by the two key steps in hierarchical assembly: (i) acid-base complex formation (as predicted by the pK of the amine) and (ii) gel fiber assembly (as predicted by the T value). These parameters therefore enable a predictive understanding of the way in which complex mixtures self-organize and assemble and also how the sorted assemblies disassemble on heating. In a key experiment, we demonstrate that these materials are highly responsive and that a preformed gel, exposed to a new component, evolves, adapts, and heals its composition in response to the thermodynamic preferences of the overall system.
AB - We report a two-component acid-amine gelation system which forms instant organogels on simple mixing. We investigate self-assembly using a wide range of different amines and identify the optimum amines for gelation to occur. Using NMR and other spectroscopic methods, we unambiguously determine the stoichiometry of the complex responsible for gelation (1:1) and characterize the noncovalent interactions responsible for gelation. Using Kamlet-Taft parameters we gain a detailed understanding of the role of solvent on gelation. Most importantly, we explore the ability of these multicomponent systems to assemble from complex mixtures, and using NMR can determine which components are preferentially taken up into the immobile "solid-like" fiber network and which components remain mobile in the "liquid-like" solvent phase. In this way, we determine that the component selection process is controlled by the two key steps in hierarchical assembly: (i) acid-base complex formation (as predicted by the pK of the amine) and (ii) gel fiber assembly (as predicted by the T value). These parameters therefore enable a predictive understanding of the way in which complex mixtures self-organize and assemble and also how the sorted assemblies disassemble on heating. In a key experiment, we demonstrate that these materials are highly responsive and that a preformed gel, exposed to a new component, evolves, adapts, and heals its composition in response to the thermodynamic preferences of the overall system.
UR - http://www.scopus.com/inward/record.url?scp=84876498263&partnerID=8YFLogxK
U2 - 10.1021/ja4017107
DO - 10.1021/ja4017107
M3 - Article
AN - SCOPUS:84876498263
SN - 0002-7863
VL - 135
SP - 5911
EP - 5920
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 15
ER -