Observation of polymer-like flow mechanism in a short-chain phosphate glass-forming liquid

The dynamics of the phosphate chains and the attendant shear relaxation in a short-chain silver phosphate glass-forming liquid with the composition 51.5%Ag₂O-48.5% P₂O₅ are studied using a combination of high-temperature ³¹P NMR spectroscopy and parallel plate rheometry. The temperature-dependent evolution of the ³¹P NMR spectral line shapes indicates that the constituent PO₄ tetrahedral chains in this liquid undergo rapid rotational reorientation. The time scale of this dynamics is in complete agreement with that of shear relaxation and, thus, must be responsible for the viscous flow of this liquid. These results demonstrate for the first time that, although the shear relaxation of the network oxide glass-forming liquids is typically controlled by the scission and renewal of bonds between the network-forming cations and oxygen atoms, such a scenario may not always be tenable for liquids with low-dimensional structures consisting of chains.