Structural control on the rheological behavior of binary P-Se supercooled liquids

Abstract

Abstract The link between the atomic structure and the shear relaxation behavior of PxSe100-x (0≤x≤25) supercooled liquids is investigated using Raman spectroscopy and parallel plate rheometry. The P atoms in these glasses form Se=P(Se1/2)3, P(Se1/2)3 and 2/2SeP-PSe2/2 units, which serve as cross-linkers of the [Se]n chain segments. The frequency dependence of the storage and loss moduli as well as the relaxation spectra H(τ) indicate that liquids with >85% Se are characterized by the coexistence of a slow and a fast relaxation process corresponding to bond scission/renewal and Se chain segmental motion, respectively. On the other hand, liquids with ≤85% Se display only the bond scission/renewal process. The H(τ) spectra suggest that the relaxation-time τ distribution for Se chain dynamics is a sensitive function of the chain length, while that for bond scission/renewal is controlled by the variety of bond types and structural moieties involved.