Ionic thermoplastic elastomers: A review

The incorporation of small amount of ionic groups into hydrocarbon polymers results in unique physical properties and these polymers are called ionome rs. They are effectively cross-linked through the association of ionic grou ps, forming multiplets or clusters. These associations are thermally labile to a greater or lesser extent depending on the composition of the ionic do mains. In elastomeric ionomers, the thermolabile nature of the ionic domain s permits the adequate flow at the processing temperatures. and hence the t erm ionic thermoplastic elastomers. Polar plasticizers are incorporated int o 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 therm al stability and high temperature performance, The presence of ion-ion inte ractions in different rubber/plastic blends enhances the mechanical compati bility of the otherwise incompatible blends and thereby results in the form ation of ionic thermoplastic elastomers, depending on the rubber to plastic ratios. In the absence of ionic groups the blend components are incompatib le, as indicated by poor physical properties of the blends. However, the in troduction of ionic groups onto the polymer chains causes a dramatic increa se in compatibility between the rubbery and the plastic phases, as indicate d by the synergism in physical properties. The present paper reviews the io nic thermoplastic elastomers based on elastomeric ionomers, block copolymer ionomers, and ionomeric polyblends.