Terminal relaxation behavior of entangled linear polymers blended with ring and dumbbell-shaped polymers in melts

We investigated the terminal relaxation behavior of entangled linear polystyrene L430 (with the entanglement number Z = M/M_e ≃ 24, where M is the molecular weight and M_e is the entanglement molecular weight) blended with ring R30 (M_R ≃ 1.8 M_e) and dumbbell-shaped D308030 (M_R ≃ 1.8 M_e and M_L ≃ 4.7 M_e) polymers. The L430/R30 blend exhibits a one-step relaxation unlike binary linear polymer blends with different molecular weights. The zero-shear viscosity η₀ of the L430/R30 blend is slightly lower than that of the neat L430. These results suggest that spontaneous penetration of the linear chains into the rings occurs, but the rings do not act as entanglement cross-linkers. The L430/D308030 blend also exhibits a one-step relaxation, but its terminal relaxation is slower and broader than that for L430. This result is probably because two ring sections in D308030 are penetrated by the linear chains, and hence D308030 acts as a pseudo-entanglement point with longer characteristic time. Graphical abstract: [Figure not available: see fulltext.]