Rheology of supercooled Se-Te chain liquids: Role of Te as an interchain cross-linker

Abstract The shear relaxation behavior of supercooled SexTe100-x (70 ≤ x ≤ 95) liquids are studied using oscillatory parallel plate rheometry. The difference in the relaxation timescales of the slow bond scission/renewal dynamics and the fast segmental chain motion that coexist in Se decreases monotonically with progressive addition of Te, until only one relaxation process can be identified in the Se70Te30 liquid. This evolution of the relaxation dynamics mimics the rheological behavior of Ge/As-Se liquids, when traditional chain crosslinkers such as Ge/As is added to Se. This finding suggests that the Te atoms serve as pseudo-crosslinkers via secondary bonding interactions between adjacent [Se,Te]n chains. This interchain interaction results in a lowering of the motional degrees of freedom of the constituent chains in SexTe100−x liquids in the supercooled region. However, the compositional invariance of the superliquidus viscosity of these liquids suggests that the interchain interaction constraint can be lifted at high temperatures.