Nonequilibrium Behaviors of Entangled Diblock Copolymers at the Entangled Polymer-Polymer Interface under Steady Shear Flow.

Abstract

The slip phenomena and the individual configuration dynamics of interfacial copolymer chains in the entangled polymer-polymer interface under fast shear flow are analyzed using mDPD simulations on ternary blends of A125/B125/C125D125 with different incompatibilities or interface strengths. We observe two distinct power-law regions of slip velocity against interfacial shear stress: from Vs ∼ σ5 to Vs ∼ σ1 at an increasing shear rate with the interface strength. At the micro level, the two regions correspond to the integrated and incomplete interfacial entanglement network with the shear-induced disentanglement of interfacial chains, respectively. For the individual chain dynamics of interfacial copolymers, we clarify that for the weak incompatibility, the tumbling event of interfacial copolymer chains is irregular and occasional and includes six processes: align and flip, collapse, tumble, stretch, reflip, and recoil and tumble. For the system with strong incompatibility, the interfacial copolymer chain undergoes the stretched-coil conformational transition via elastic retraction. As the interfacial entanglement network disintegrates, the hairpin-like configuration is dominant during the tumbling motion or elastic retraction of the interfacial copolymer chain.