Modulated morphology in the self-organization of a rectangular amphiphile.
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, pi-pi 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) approximately 5.2 x 10(5) M(-1) for CH3CN/H2O mixtures and 4.4 x 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.
García
Fátima
F
Departamento de Química Orgánica, Facultad de Ciencias Químicas, Ciudad Universitaria s/n. 28040 Madrid, Spain.
Fernández
Gustavo
G
Sánchez
Luis
L
D008823:Micelles; D015394:Molecular Structure; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D008823:Micelles; D011108:Polymers; C473966:poly(phenylene ethynylene)