Ionomers are those hydrophobic polymers having small amounts of bonded ionic groups. The introduction of the ionic groups into polymer chain produces large changes in the physical, mechanical and rheological properties of the parent polymer. In this book, low molecular weight (Mw=4000) sulfonated polystyrene (SPS) was used to study the dynamic and steady shear rheology of SPS ionomers. This polymer was chosen since the effects of molecular entanglements will be excluded. Any polymer chain entanglements or lengthening behavior on the melt rheology should be due to the ionic interactions. Some intriguing results were found in this study.