Mimicking nature: Biomimetic ionic channels

• Published in: Journal of membrane science 2016-07, Vol.509, p.10-18
• Main Authors: Bogdanowicz, Krzysztof A., Bhosale, Suryakant V., Li, Yun, Vankelecom, Ivo F.J., Garcia-Valls, Ricard, Reina, José A., Giamberini, Marta
• Format: Article
• Language: English
• Subjects: Bioinspired; Channels; Diffraction; Exploitation; Impedance; Ionic channels; Liquid-crystalline polyethers; Membranes; Proton conductivity; Relative humidity; State of the art; Transmission electron microscopy; Transport
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2016.02.038

Membranes with a high but remarkably humidity-independent proton conductivity were prepared. Side-chain liquid crystalline polyethers (SCLCPs), based on poly(epichlorohydrin) (PECH) and poly(epichlorohydrin-co-ethylene oxide) (P(ECH-co-EO)), dendronized with potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate were specially designed for this purpose. When cast as membranes, these tailored polymers self-assembled into columns, driven by exo-recognition. They thus mimic the highly specific supramolecular organization observed in nature and present the first biomimetic material for proton transport out of which stable, oriented and self-sustained membranes could be prepared. As revealed by combined X-ray diffraction, Atomic Force Microscopy and Transmission Electron Microscopy, polymeric column formation was obtained in the cast membranes following a thermally induced homeotropical orientation. Two unique and highly desired properties were found in the resulting membranes. While conventional proton conducting membranes exploit an “acidic group-based” transport mechanism, the current columns pillaring across the membranes formed ionic paths, giving rise to a remarkable size-dependent antiport transport mechanism. It resulted in conductivity values in the range of 10−2–10−3S/cm, comparable to current state-of-the-art Nafion membranes, but, most importantly, with a complete independency from relative humidity. Reported membranes thus open excellent opportunities for further fine-tuning of their properties, wider exploitation of the exceptional transport mechanism, and final applications in fuel cells and related fields. [Display omitted] •Novel proton-transport membranes, based on dendronized polyethers are prepared.•Biomimetic ion channels via columnar polymer self-assembling are formed.•Antiport ion-size-dependent transport is observed.•Proton conductivity comparable to Nafion®'s and water content independent is found.