NMR investigation of charge transfer complexes in amphiphile solutions and polymer/amphiphile comb-like structures

Charge transfer (CT) complexation has been investigated in two self-associating systems, including amphiphile aggregation in aqueous solutions and formation of comb-like polymer/amphiphile complexes in the solid state.; 1H NMR, 2D Nuclear Overhauser Effect Spectroscopy (NOESY) and spin-lattice relaxation time (T₁) measurements were used to investigate the aqueous solution behavior of poly(ethylene glycol) monomethyl ether 3,5-dinitrobenzoate (PEG-DNB). Intramolecular CT complexation between the PEG chains and the dinitrobenzoyl group was found to be the cause of the unusual phase behavior and 1H NMR multiplet patterns. The molecular weight resolution observed in the 1H NMR spectra was correlated to the different conformations adopted by complexes having different PEG lengths.; 1H NMR relaxation times, Pulse Field Gradient Spin-Echo (PFG SE) NMR self-diffusion coefficients and Small Angle X-ray Scattering (SAXS) were used to investigate the aggregation in aqueous solutions of PEG-DNB. Small core/shell aggregates of about 4 surfactant molecules were detected in dilute solution. In concentrated solutions (>4 wt %), CT complexation produces a new type of large composite aggregates where the driving force for aggregation is the polydispersity of the PEG chains. The size of the aggregates, between 7 and 11 rim as determined from SAXS, was correlated to the molecular weight polydispersity of the PEG chains.; Hydrophobic N-ethylcarbazole (NEK) was solubilized in aqueous solutions by the complex PEG-DNB surfactant. CT interactions between the NEK solute and the hydrophobic part of the surfactant, the DNB group, favors the solubilization process. The symmetric coplanar sandwich geometry of the NEK/DNB complex does not interfere with the PEG/DNB complex due to sidewise orientation of the polyether chain. Thus, DNB forms complexes simultaneously with a π-electron donor, NEK, and a n-electron donor, PEG. Dissolving LiClO₄ in aqueous solutions of PEG-DNB produces decomplexation. Li+ cations form ion-dipole interactions with PEG and remove it from its coiled complex with DNB.; Solid state NMR was used to investigate the macromolecular CT complexes formed between poly(N-vinylcarbazole) (PVK) and PEG-DNB. The balance between the PVK/DNB CT interactions and the repulsion between the PVK backbone and the PEG side chains produces comb-like structures similar to those observed in polyelectrolyte/surfactant complexes. The size of the domains in these microphase separated comb-like CT complexes was evaluated based on proton spin diffusion analysis.