ORIENTATIONAL ORDERING AS A POSSIBLE MECHANISM FOR VISCOSITY-ENHANCEMENT OF SUPERCOOLED LIQUIDS

A supercooled liquid is viewed to have regions of local orientational order which can be pictured in terms of cages that restrict single-particle diffusion. The mismatch in the orientation of two locally ordered neighbouring regions causes an internal stress which is added to the stress that appears in the Maxwell model of viscoelasticity. This leads to a renormalized Maxwell time which is related to the relaxation time and the susceptibility associated with the orientational order. Hence, when either the relaxation time or the susceptibility becomes very large, one obtains a large enhancement of the viscosity.