Permeability-controllable membranes. 7. Electrochemical responsive gate membranes of a multibilayer film containing a viologen group as redox sites

Abstract

peaks and large frequency shift observed in the FT-IR spectra along with the occurrence of low-energy absorption bands (CT2 band) in the electronic absorption spectra (extending into IR region) indicate that these charge carriers are migrating along the TCNQ molecules. Thus, the TCNQ molecules are stacked in columns.This stacking is affected by the surrounding dications via the structural configuration and periodicity of the electric potential.The stoichiometry of TCNQ evaluated from the results of elemental analysis is, in most of the cases, close to 4.5. This number becomes smaller for shorter dications. It is known that in TCNQ salts, TCNQ molecules are sometimes arranged in tetrads or pentads in the TCNQ columns.5-7,14 Hence, it is reasonable to expect that there are two tetrads sharing an extra TCNQ molecule in the crystal lattice of these salts. Assuming a uniform distribution of charges among these TCNQ molecules, a value of -0.44 fractional charges is obtained. However, the fractional charge is evaluated to be -0.56 to -0.7 on the basis of the frequency shift of infrared peaks. Thus, neutral TCNQ molecules very likely exist in the stacks. Migration of charge from charged to neutral TCNQ molecules is indeed observed in the electronic absorption spectra (CT2 band). The difference in conductivity by 3 orders of magnitude for C3 and C4 salts could be due to the larger separation between the tetrads (CT2 bands located at ~2000 and >2500 nm, respectively).It would be very helpful to have single crystals of these salts to study their properties. More efforts are currently underway to obtain these and also for elucidation of the conduction mechanism. More affirmative evidence is needed to show if the length made by four or five singly bonded carbon atoms is the best match for giving high conductivities. This could be important in future design of polymeric conductors.

Self-Assembled Polyelectrolyte−Surfactant Complexes in Nonaqueous Solvents and in the Solid State

“…Membranes with permeability switched by small electric fields have been prepared from complexes of poly-(styrenesulfonate) with viologen-containing dialkyl sulfates, in which the temperatures of the liquid-solid transitions of the alkyl chains can be controlled by redox reactions of the headgroups. 45,46 Complexes of Synthetic Polypeptides. (1) Conformation of Polypeptide Chains.…”

“…Complexation of polyelectrolytes with surfactants capable of reversible structural rearrangement has been used to prepare membranes with controlled permeability. Membranes with permeability switched by small electric fields have been prepared from complexes of poly(styrenesulfonate) with viologen-containing dialkyl sulfates, in which the temperatures of the liquid−solid transitions of the alkyl chains can be controlled by redox reactions of the headgroups. , …”

Dielectric and Mechanic Relaxation in Polyelectrolyte-Supported Bilayer Stacks: A Model for the Dynamics of Membranes?

“…Polyelectrolyte-surfactant complexes (PE−surfs) consisting of a charged polymer and oppositely charged surfactants form highly defined structures in the bulk. − In the last years, it was shown that this building principle can be extended toward the complexation of bilayer-forming lipids, − thus combining the stack-of-bilayer structure of the lipid mesophases with the mechanical properties of the polyelectrolyte backbone.…”

Synthesis and characterization of viologen‐containing poly(vinylidene fluoride) redox‐sensitive membranes

“…4 -7 The methods used include plasma treatment, blending with hydrophilic polymers, and ion beam irradiation. 8 -11 A redox-active property has also been introduced on multi-bilayer film 12 and poly(pyrrole-viologen) films, 13 and controllable reversible permeability and release of chemicals can be achieved. In the present work, we report on the synthesis and characterization of the PVDF membrane with grafted viologen moieties.…”