Revisiting the Intrinsic Nonlinearity Dilution in Model Polystyrene Combs under Medium-Amplitude Oscillatory Shear

Abstract The effect of dynamic tube dilution (DTD) on medium-amplitude oscillatory shear (MAOS) responses was examined for model polystyrene combs with unentangled and entangled branches. First-harmonic MAOS plateau moduli followed the same dilution scaling as linear viscoelasticity with dilution exponent α = 1, whereas third-harmonic nonlinearity Q0 was more strongly diluted than expected from static dilution. In multimode molecular stress function analysis, the first-harmonic response was well described with stretch parameter β = 1 regardless of topology, whereas larger effective β values improved the third-harmonic predictions for combs. These results indicate an additional topology-sensitive third-harmonic contribution beyond DTD alone.