Ionic clusters description

An introduction to the non-covalent forces operating in stable ionic and molecular aggregates will be presented in Section 2. A brief description of the experimental methodologies employed in the production, detection, and characterization of clusters will be given in Section 3. The available experimental evidence on the structure of chiral clusters and their intrinsic stability, reactivity, and evolution dynamics will be presented and discussed in Sections 4 (molecular clusters) and 5 (ionic clusters). In the same sections, the experimental data will be interpreted in the light of the available theoretical evidence. Finally, some concluding remarks will be expressed in Section 6. 

The original cluster-network model proposed by Gierke et al. (also referred to as the cluster-channel model) has been the most widely referenced model in the history of perfluorosulfonate ionomers. Despite the very large number of papers and reports that have strictly relied on this model to explain a wide variety of physical properties and other characteristics of Nafion, this model was never meant to be a definitive description of the actual morphology of Nafion, and the authors recognized that further experimental work would be required to completely define the nature of ionic clustering in these iono-mers. For example, the paracrystalline, cubic lattice... 

It is certainly interesting to see here that the DFT treatment is able to provide us with a realistic description of these interaction forces which are likely to play a mayor role in the dynamics of cluster growth. It does so by markedly reducing the computational effort and thereby making amenable to computations ionic clusters of reahstic sizes. Furthermore, it shows very good agreement with the fully ab initio calculations which aheady exist on the smaller species and with which comparison has been possible. 

Bicontimous network of ionic clusters Elliott and co-workers demonstrated a unified morphological description of PFSAs based on both statistical (MaxEnt) and thermodynamic (DPD) descriptions, which broadly favours a bicontinuous network of ionic clusters embedded in a matrix of fluorocarbon chains. Elliott, 201 The existence of a continuous network of water-filled channels explains the high water diffusion coefficient of water in Nafion. 

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