Nonlinear Rheology of Random Sulfonated Polystyrene Ionomers: The Role of the Sol–Gel Transition

摘要: The linear and nonlinear rheological behaviors of nonentangled sulfonated polystyrene (SPS) ionomers near the sol–gel transition were studied. When degree sulfonation, p, was below gel point, ionomer exhibited sol-like viscoelastic (LVE) behavior, shear thinning observed for steady flow. For p close to showed power-law-like LVE behavior over a wide frequency range. Strain hardening thickening observed, their magnitudes depended on temperature, molecular weight PS precursor, Coulomb energy ion pair. Above distinct rubbery plateau in dynamic modulus. Melt fracture occurred upon start-up shear, which prevented quantitative examination rheology. possible mechanisms strain point are discussed with respect formation large clusters that nearly percolate space.