Polystyrene based sulfonate ionomers

In this work we used polystyrene-based ionomers.-Since there is no crystallinity in this type of ionomer, only the effect of ionic interactions has been observed. Eisenberg et al. reported that for styrene-methacrylic acid ionomers, the position of the high inflection point in the stress relaxation master curve could be approximately predicted from the classical theory of rubber elasticity, assuming that each ion pah-acts as a crosslink up to ca. 6 mol %. Above 6 mol %, the deviation of data points from the calculated curve is very large. For sulfonated polystyrene ionomers, the inflection point in stress relaxation master curves and the rubbery plateau region in dynamic mechanical data seemed to follow the classical rubber theory at low ion content. Therefore, it is generally concluded that polystyrene-based ionomers with low ion content show a crosslinking effect due to multiplet formation. More... 

Arguably the most important amorphous ionomer is sulfonated polystyrene (SPS). Other ionomers include poly(styrene-rfln-methacrylic acid) (SMAA), polyurethanes, siloxanes, butadiene-based elastomers, ethylene-propylene-diene terpolymers, acrylates and methacrylates, polyphosphoesters, polyimides, and many others. ... 

Reference 7 reviews a number of electron microscopy studies of ionomer morphology in the period up to 1979. None of these studies makes a convincing case for the direct imaging of ionic clusters. This is because of the small size of the clusters (less than 5 nm based on scattering studies) and difficulties encountered in sample preparation. The entire problem was reexamined in 1980(21). In this study ionomers based on ethylene-methacrylic acid copolymers, sulfonated polypentenamer, sulfonated polystyrene and sulfonated ethylene-propylene-diene rubber (EPDM) were examined. The transfer theory of imaging was used to interpret the results. Solvent casting was found to produce no useful information about ionic clusters, and microtomed sections showed no distinct domain structure even in ionomers neutralized with cesium. Microtomed sections of sulfonated EPDM, however,... 

The perfluorinated, carboxylated and sulfonated ionomer membranes form the ionic clusters of a few nm in size, as in the case of the hydrocarbon-based ionomers such as polyethylene,polystyrene and polybutadiene(9). The ionic clusters strongly affect physical properties of the membranes, e.g., the swelling behavior of the membranes (amount of water uptaken by the membranes, W and... 

Several non-fluorinated alternative polymers have been proposed for DAFC, mainly based on sulfonated ionomers with an aromatic or aliphatic hydrocarbon skeleton [7], Kim and Pivovar [4] have reported the number of DMFC alternative membranes papers appearing in open hterature for years 1994—2004, showing that polyarylenes, polyvinyl alcohols, grafted and block polystyrenes copolymers, and polyimides were among the most studies polymer electrolytes. In view of the dramatic increase in the number of publications since 2005 (see Fig. 6.1), the trends have changed, as shown in Table 6.1, which sununaiized the publications in open literature for the period 2005-2012, as compared to the previous period. 

In nonrigid ionomers, such as elastomers in which the Tg is situated below ambient temperature, even greater changes can be produced in tensile properties by increase of ion content. As one example, it has been found that in K-salts of a block copolymer, based on butyl acrylate and sulfonated polystyrene, both the tensile strength and the toughness show a dramatic increase as the ion content is raised to about 6 mol% [10]. Also, in Zn-salts of a butyl acrylate/acrylic acid polymer, the tensile strength as a function of the acrylic acid content was observed to rise from a low value of about 3 MPa for the acid copolymer to a maximum value of about 15 MPa for the ionomer having acrylic acid content of 5 wt% [II]. Other examples of the influence of ion content on mechanical properties of ionomers are cited in a recent review article [7],... 

The use of ionomers such as lightly sulfonated polystyrene as an oil-based fracturing fluid viscosifier has been studied (70). 

Mani S, Weiss RA, Williams CE, Hahn SF. Microstructure of ionomers based on sulfonated block copolymers of polystyrene and poly(ethylene-afe-propylene). Macromolecules 1999 32 3663-3670. 

To be informative, it is desirable that the comparisons of these two different technologies be based on identical polymer backbones, having identical molecular weights, and having comparable levels of ionic functionality present. In addition, it is the purpose of these studies to make such comparisons with the same metal cation and thereby quantify, insofar as possible, the nature of the ionic interactions that exist. To do this, ionomers were prepared based on a polystyrene (PS) hydrocarbon backbone into which the ionic functionality was incorporated. PS was selected as the backbone because of the relative ease of functionalization and the relative freedom of side reactions during the sulfonation or carboxylation reactions. The polymers prepared were designed to come as close as possible in terms of ionic functionality for both sulfonate and carboxylate ionomers over a range of ionic contents. 

Eisenbach C D, Hofmann J and MacKnight W J (1994) Dynamic-mechanical and spectroscopic study of ionomer blends based on carboxylated or sulfonated flexible polystyrene and rigid poly(di-acetylenes) with functional side groups. Macromolecules 27 3162-3165. 

Figure 3 schematically illustrates the interference model where it is assumed that the ionomer peak arises from a preferred interparticle distance. Recently, Yarusso and Cooper have proposed an interpretation of the ionomer peak which is based on the liquid-like scattering from hard spheres originally described by Fournet. The Fournet model is quantitatively capable of fitting the X-ray peak from sulfonated polystyrene ionomers. In the case of zinc-neutralized material, about half of the ionic groups were found to aggregate into well ordered domains ( clusters ) with the remainder... 

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