Neutron scattering, ionomers

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

Recently, Ioselevich, Kornyshev, and Steinke (IKS) suggested a more detailed morphological model of Nafion-type ionomers [61], which has questioned the existence of pores in homogenous ionomers such as Nafion at least in normally hydrated state. The model was based on neutron scattering data showing... 

Various techniques have been used to study the solution properties of ionomers. These include viscosity (4, 1 ), static and dynamic light scattering (12.13.15-18), small-angle neutron scattering (11.14). and spectroscopy (10). Here, we use (static and... 

The extent of aggregation observed by small-angle neutron scattering Is very dependent on concentration In agreement with light scattering and solution viscosity studies. These measurements on SPS solutions are expected to apply In general to Ionomer solutions In low polarity solvents with appropriate considerations for polymer architecture and counterion structure. 

Most of the research effort on the ionomers has been devoted to only a small number of materials, notably the ethylenes the styrenes, the rubbers(9)5 and those based on poly(tetra-fluoroethylene), the last of which is the subject of the present volume. As a result of these extensive investigations, it has become clear that the reason for the dramatic effects which are obsverved on ion incorporation is, not unexpectedly, the aggregation of ionic groups in media of low dielectric constant. Small angle X-ray and neutron scattering, backed up by a wide range of other techniques, have demonstrated clearly the existence of ionic... 

As in other ionomers, the ion exchange sites in "Nafion" membranes are observed to aggregate and form clusters. Ionic clustering in "Nafion" membranes has been indicated by a variety of physical studies including dielectric relaxation (1), small angle x-ray scattering (1-4), neutron scattering (4), electron micro-... 

Finally, extensions of the techniques to other materials are obvious. Some are straightforward if they involve a melt close to a glass transition or if they are very viscous this depends only on the possibilities of the chemistry of deuteration star and ring polystyrene, blends, ionomers, and possibly semirigid polymers and compatible copolymers. The use of other techniques (Sect. 2) would be required for more liquid materials, as multicomponent solutions, where again neutron scattering has no equivalent. 

The analysis of RDFs, gy (ry), provides valuable stmctural information of simulated many-particle systems. It allows rationalizing structural correlations between atoms or beads, aggregation behavior, and phase separation, as well as sizes, shapes, and coordination structure of distinct phase domains. Experimentally, the RDF is obtained from the structure factor S(q), which determines the intensity of x-ray or neutron scattering (Ashcroft and Mermin, 1976). The structure factor for scattering from phase domains formed by a single component, for example, apolar beads in fibrils of ionomer backbones, is given by... 

Kumar, S. and Pineri, M. (1986) Interpretation of small angle X-ray and neutron scattering data for perfluorosulfonated ionomer membranes, J. Polym. Sci. Polym. Phys. Ed., 24, 1767-1782. 

Aldebert, R, Dreyfus, B., and Pineri, M. (1986) Small-angle neutron scattering of per-fiuorosulfonated ionomers in solution, Macmmolecules, 19, 2651-2653. 

Gebel, G. and Diat, O. 2005. Neutron and x-ray scattering Suitable tools for studying ionomer membranes. Fuel Cells 5 261-276. 

A typical behavior observed in ionomers is the existence of a small angle scattering peak (from X ray or neutron experiments) and a zero... 

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