A direct test of the correlation between elastic parameters and fragility of ten glass formers and their relationship to elastic models of the glass transition

Abstract

We present an impulsive stimulated scattering test of the "shoving model" of the glass transition and of the correlation between the fragility index and the ratio of instantaneous elastic moduli of eight supercooled liquids. Samples of triphenyl phosphite, DC704 (tetramethyl tetraphenyl trisiloxane), m-fluoroaniline, Ca(NO(3))(2)4H(2)O, diethyl phthalate, propylene carbonate, m-toluidine, phenyl salicylate (salol), 2-benzylphenol, and Santovac 5 (5-phenyl 4-ether), were cooled to their respective glass transition temperatures and the elastic moduli directly measured at the highest accessible shear frequencies. The shear modulus was then measured every 2 K as deeply as permitted into the liquid state for all liquids except propylene carbonate. Our results, in conjunction with dynamical relaxation data for these liquids obtained from the literature, lend credence to the notion that the dynamics of the glass transition are governed by the evolution of the shear modulus but do not suggest a strong correlation between the fragility index and the ratio of the elastic moduli.