VISCOELASTIC BEHAVIOR OF PLASTICIZED SULFONATED POLYSTYRENE IONOMERS

Two different approaches for modifying the linear viscoelastic behavior of an ionomer, lightly sulfonated polystyrene (SPS), are described. Adding a backbone plasticizer, such as dioctyl phthalate (DOP), affects that part of the relaxation behavior due to the backbone polymer. Thus, DOP lowered the primary glass transition temperature without affecting the relaxation time spectrum associated with the ionic clusters. However, an ionic domain plasticizer, such as glycerol, affects the relaxation of the ionic clusters and has little or no effect on the viscoelastic response of the nonpolar phase. For SPS, the addition of glycerol shifted the long-time relaxations associated with the ionic clusters to shorter times, thus decreasing the melt viscosity and reducing the networklike response due to physical associations of the ionic groups.