Craig Versek

Enhancement of anhydrous proton transport by supramolecular nanochannels in comb polymers

Transporting protons is essential in several biological processes as well as in renewable energy devices, such as fuel cells. Although biological systems exhibit precise supramolecular organization of chemical functionalities on the nanoscale to effect highly efficient proton conduction, to achieve similar organization in artificial systems remains a daunting challenge. Here, we are concerned with transporting protons on a micron scale under anhydrous conditions, that is proton transfer unassisted by any solvent, especially water. We report that proton-conducting systems derived from facially amphiphilic polymers that exhibit organized supramolecular assemblies show a dramatic enhancement in anhydrous conductivity relative to analogous materials that lack the capacity for self-organization. We describe the design, synthesis and characterization of these macromolecules, and suggest that nanoscale organization of proton-conducting functionalities is a key consideration in obtaining efficient anhydrous proton transport.

Physicochemical properties of 1,2,3-triazolium ionic liquids

Ionic liquids composed of four different 1,2,3-triazolium cations with tosylate or triflate counter anions have been synthesized and characterized. Physicochemical properties of these ionic liquids including ion cluster behavior, thermal properties, electrochemical stability and ionic conductivity were determined and compared to corresponding imidazolium based ionic liquids. The impact of structure variations, in terms of substituents on the ring of the 1,2,3-triazolium cation and identity of the anion (i.e. tosylate versus triflate) is discussed. Stability of the 1,2,3-triazolium salts towards hydroxide ion at 80 °C was studied. Key features of 1,2,3-triazolium salts are their high electrochemical stability and ionic conductivity, comparable to imidazolium ionic liquids, but better chemical stability under alkaline conditions.

Anhydrous proton conductivities of squaric acid derivatives

In this communication, we introduce squaric acid derivatives as anhydrous proton conductors. We report the synthesis, characterization and proton conductivities of four squaric acid derivatives. The anhydrous proton conductivity of one of the derivatives was 2.3 × 10(-3) S cm(-1) at 110 °C, comparable to the conductivity of molten 1H-1,2,3-triazole or 1H-imidazole.

Importance of dynamic hydrogen bonds and reorientation barriers in proton transport

The dynamic nature of hydrogen bonds in phenolic polymers, where the hydrogen bond donor/acceptor reorientation can occur in a single site, presents lower barriers for proton transport.

Enhanced anhydrous proton conduction in binary mixtures of 1H-imidazole–1H-1,2,3-triazole based compounds

What is the impact of mixing two proton-conducting heterocycles on proton conductivity? Herein we answer this question through our investigations on two linear rod-like compounds 2-(4-(dodecyloxy)phenyl)-1H-imidazole (4) and 5-(4-(dodecyloxy)phenyl)-1H-1,2,3-triazole (10). We have found that mixtures of molecules 4 and 10 at certain compositions show enhanced proton conductivity compared to their pure components. We attribute the increased conductivity in these materials to the increased charge density due to facile co-ionization and increased mobility due to the incorporation of long alkyl chains, which prevent crystallization of protogenic groups while maintaining the required hydrogen bonded network. Our results suggest a new strategy for enhancing intrinsic proton conductivity in heterocyclic systems.