Blending of Ionizable Polymers: Molecular Dynamics Simulation Study

Ionomer containing polymers blends exhibit the potential to incorporate the unique transport ability of ionomers with the viscoelasticity of non-ionic macromolecules,  opening the way to a broad range of innovative technologies currently hampered by the challenge that under the conditions where transport is optimized, mechanical stability is often reduced.  Similar to blending highly incompatible polymers, mixing of ionizable polymers in non-ionic ones presents significant challenges. Here using molecular dynamics simulations, we probe blending of associating polymers using a bead-spring model as the strength of the associative groups is varied from 1 to 10KT.  In parallel, we probe the structure evolution and dynamics of blends of polystyrene and sulfonated polystyrene of different sulfonation fractions. Cluster characteristics including size, shape and internal packing are extracted and correlated with the static structure factor S(q). S(q) is fit with the random phase approximation model (RPA) and the degree of segregation is extracted. Surprisingly, atomistic simulations of PS and PSS blends reveal a higher compatibility than expected.  The correlation between associating bead interactions strength and the degree of phase segregation will be discussed.