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Modulated Morphology in the Self‐Organization of a Rectangular Amphiphile
Author(s) -
García Fátima,
Fernández Gustavo,
Sánchez Luis
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900303
Subject(s) - solvophobic , supramolecular chemistry , van der waals force , amphiphile , hydrogen bond , chemistry , vesicle , self assembly , solvent , micelle , chemical physics , intermolecular force , covalent bond , random hexamer , crystallography , stacking , non covalent interactions , aqueous solution , molecule , organic chemistry , copolymer , polymer , membrane , crystal structure , biochemistry
Molecular construction : Concentration and/or solvent polarity changes modify the subtle balance of the attractive non‐covalent forces involved in the self‐assembly of a rectangular amphiphile. These changes allow the construction of supramolecular architectures ranging from hollow vesicles of different sizes to toroids and wire‐like micelles (see figure).The rectangular oligo(phenylene ethynylene) amphiphile 1 has been synthesized to investigate its self‐assembling features in solution and onto surfaces. Concentration‐dependent and variable‐temperature NMR experiments firstly demonstrate the influence of the solvent in the stabilization of the non‐covalent forces involved in the association of 1 , namely, π–π stacking interactions between the aromatic fragments and van der Waals, hydrogen‐bonding and/or solvophobic forces between the triethyleneglycol chains. This subtle balance of non‐covalent interactions also conditions the thermodynamics of the self‐assembly process and concentration‐dependent UV/Vis investigations show a linear correlation between the polarity of the solvent and the K a values ( K a ≈5.2×10 5 M −1 for CH 3 CN/H 2 O mixtures and 4.4×10 4 M −1 for benzene). Moreover, these UV/Vis studies prove the organization of this compound following the indefinite self‐association model. Microscopy techniques reveal that the morphology and dimensionality of the assemblies formed from 1 can be finely modulated. Although polar solvents yield hollow vesicles or toroidal 3D objects, depending upon concentration, the utilization of non‐polar benzene results in the formation of unimolecular wires that can grow to form networks upon increasing concentration. These findings support the direct relationship existing between the self‐assembling features of this amphiphile in solution and onto surfaces.