Polymers of intrinsic microporosity in electrochemistry: Anion uptake and transport effects in thin film electrodes and in free-standing ionic diode membranes

Abstract

Anion uptake and charge transport in a Polymer of Intrinsic Microporosity (here PIM-EA-TB) is investigated for three cases: (i) the oxidation of ferrocene embedded into a thin film of PIM-EA-TB on a glassy carbon electrode, (ii) the reduction of protons absorbed into a thin film of PIM-EA-TB on a platinum electrode, and (iii) the potential-driven transport of anions and protons in an asymmetrically deposited free-standing PIM-EA-TB membrane working as a current rectifier or "ionic diode". In all three cases the competing effects of the diameter and hydrophobicity (size and hydration energy) of the anion are important. For free-standing membranes very high ionic diode rectification ratios (>10 3 at +/-1 V) are observed in particular for thicker deposits of PIM-EA-TB and for chloride or perchlorate containing electrolyte.

pH-induced reversal of ionic diode polarity in 300 nm thin membranes based on a polymer of intrinsic microporosity

“…Chronoamperometry data in Figure 2Bii show that, when switching the potential from -1 V to +1 V, the current switches from -0.02 A to 1.6A, suggesting a difference in mobility for Na + and OH -in PIM-EA-TB causing a reversal of the ionic diode polarity. Data in Figure 2C and 2D show the gradual change in rectification effects with pH consistent with an approximate pK A for PIM-EA-TB at pH 4 [23]. Figure 3C).…”

“…soluble in organic solvents for casting of films and membranes [17]) and highly porous with typical BET surface area values ≈1000 m 2 g -1 [18]. Initial work focused on the gas-phase, but recently also liquid-phase applications have been explored based on stabilisation of fuel cell catalysts [19], "heterogenisation" of molecular catalysts [20,21], formation of novel microporous heterocarbon structures [22], and current rectification [23]. In previous work we employed solution casting methods to give relatively thick (typically 10 m or more) PIM membranes.…”

A highly rigid and gas selective methanopentacene-based polymer of intrinsic microporosity derived from Tröger's base polymerization

“…9,10 In particular, PIMs with the ability to form exible, robust, self-standing lms have potential as membrane materials for anionic transport, 11 the separation of gases, vapours 12 or for nanoltration. 13,14 Their exceptional potential for gas separation 15,16 is based on the high free volume generated from the inability of their contorted polymer chains to pack efficiently, which provides high permeability, while the lack of conformational freedom and rigidity, due to their fused-ring structures, ensures good permselectivity.…”

Ionic Diodes Based on Regenerated α‐Cellulose Films Deposited Asymmetrically onto a Microhole

“…Ionic diode devices generally require asymmetry of charge carrier mobility, which can be achieved in single channel nanopores with chemical modification by employing cone‐shaped pores, at polyelectrolyte junctions, and electrolyte ‐ ionomer‐membranes ‐ electrolyte junctions 7 with asymmetry in the interfacial contact zone. Recently, we have reported on the ionic diode effects utilizing the asymmetric deposition of polymers of intrinsic microporosity (PIM) membranes using a molecularly rigid Tröger base polymer (PIM‐EA‐TB) . In these cases the combination of a macroscopic asymmetry in film deposition, as well as the charge distribution and microscopic pore structure, were suggested to lead to ionic diode behaviour.…”