Ionic aggregates ethylene ionomers

The ionic aggregates present in an ionomer act as physical crosslinks and drastically change the polymer properties. The blending of two ionomers enhances the compatibility via ion-ion interaction. The compatibilisation of polymer blends by specific ion-dipole and ion-ion interactions has recently received wide attention [93-96]. FT-IR spectroscopy is a powerful technique for investigating such specific interactions [97-99] in an ionic blend made from the acid form of sulfonated polystyrene and poly[(ethyl acrylate - CO (4, vinyl pyridine)]. Datta and co-workers [98] characterised blends of zinc oxide-neutralised maleated EPDM (m-EPDM) and zinc salt of an ethylene-methacrylic acid copolymer (Zn-EMA), wherein Zn-EMA content does not exceed 50% by weight. The blend behaves as an ionic thermoplastic elastomer (ITPE). Blends (Z0, Z5 and Z10) were prepared according to the following formulations [98] ... 

Grady, B.P. Goossens, J.G.P. Wouters, M.E.L. Morphology of zinc-neutralized maleated ethylene-propylene copolymer ionomers structure of ionic aggregates as studied by x-ray absorption spectroscopy. Macromolecules 2004, 37, 8585. 

Winey, K.I. Laurer, J.H. Kirkmeyer, B.P. Ionic aggregates in partially Zn-neutralized poly-(ethylene-ran-methacrylic acid) ionomers shape, size and size distribution. Macromolecules 2000, 33, 507. 

The purpose of the present chapter is to overview recent applications of NMR to the structure and ionic aggregates of ionomers, in particular the ethylene ionomers. It is expected that more NMR studies on ionomers will be activated by this review. 

In this section, the metal-cationic salts of copoly(ethylene-methacrylic acid) are called the ethylene ionomers. This ethylene ionomer is one of the well-known commercial ionomers, marketed under the trade name Surlyn by DuPont. Many ethylene ionomers have crystalline and amorphous phases of ethylene chain units as well as polyethylene. Therefore, there is a three-phase structure, with crystalline, amorphous, and ionic aggregate phases this is a unique characteristic of ethylene ionomers compared with other ionomers. Although the ionic aggregate structure of the ethylene ionomer has not been fully established, its structural model is represented5 as shown in Fig. 1. In ethylene ionomers, therefore, it is necessary that some physical properties should be considered by correlating to not only the ionic aggregates but also the crystalline phases. 

The characteristics of the physical properties and ionic aggregates in the ethylene ionomers have been outlined in the previous sections. The application of solid-state high-resolution l3C NMR spectroscopy to the structural analysis of ethylene ionomers33-37 is described in this section. One of the advantages of l3C NMR is to simultaneously obtain information from all phases of ethylene ionomers, i.e. crystalline, amorphous, and ionic aggregate phases. 

Figure 10 shows the 23Na MAS NMR spectra of some sodium salt ethylene ionomers at room temperature. A broad peak at about —10 to 12 ppm is clearly observed for all samples. The 23Na NMR spectra of the styrene ionomers have been reported44 (details are given in the next section, see Fig. 14). Peaks are observed at about 7, 0, and -12 to -23 ppm, which are assigned to isolated ion pairs, hydrated ions and aggregated ions respectively. The sodium cations in ethylene ionomers, therefore, are almost in ionic aggregates. The isolated ion pairs...

The morphology of ionic aggregates in semicrystalline Zn and Na-neutralized poly-(ethylene-ra -methacrylic acid) (EMAA) ionomer blown films has been studied using... 

Wang W, Tudryn GJ, Colby RH, Winey KI (2011) Thermally driven ionic aggregation in poly(ethylene oxide)-based sulfonate ionomers. J Am Chtan Soc 133 10826-10831... 

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... 

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