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Abstract
The incorporation of small amount of ionic groups into hydrocarbon polymers results in unique physical properties and these polymers are called ionomers. They are effectively cross-linked through the association of ionic groups, forming multiplets or clusters. These associations are thermally labile to a greater or lesser extent depending on the composition of the ionic domains. In elastomeric ionomers, the thermolabile nature of the ionic domains permits the adequate flow at the processing temperatures, and hence the term ionic thermoplastic elastomers. Polar plasticizers are incorporated into ion-containing polymers in order to reduce the melt viscosity, resulting from the strong ionic associations, and to improve the processability. The introduction of ionic groups into the block copolymers improves their thermal stability and high temperature performance. The presence of ion-ion interactions in different rubber/plastic blends enhances the mechanical compatibility of the otherwise incompatible blends and thereby results in the formation of ionic thermoplastic elastomers, depending on the rubber to plastic ratios. In the absence of ionic groups the blend components are incompatible, as indicated by poor physical properties of the blends. However, the introduction of ionic groups onto the polymer chains causes a dramatic increase in compatibility between the rubbery and the plastic phases, as indicated by the synergism in physical properties. The present paper reviews the ionic thermoplastic elastomers based on elastomeric ionomers, block copolymer ionomers, and ionomeric polyblends.