Behavior of glass and supercooled liquid Alkylbenzenes vapor-deposited on cold substrates: Toward the understanding of the curious light scattering observed in some supercooled liquid states

Abstract

Ethylbenzene (EB) films prepared on cold metal substrates by vapor deposition in vacuum show a curious light scattering in the supercooled liquid (SCL) state when the temperature israised at a constant rate. To investigate the cause of this phenomenon, we examined the behavior of similarly prepared samples of a series of alkylbenzenes. We found that the vapor-deposited glass of propylbenzene (PB) and isopropylbenzene (IPB) showed a deposition-temperature (Td) dependence of the initial molar volume (Vm) on deposition similar to EB glass. Interestingly, the samples of the three compounds, which were formed initiallyas glasses with Vm much larger than that of SCL at the same temperature, exhibited the curious light scattering when they transformed to SCL states after the temperature elevation to above their glass-transition temperature, while the corresponding samples with initial Vm smaller than that of SCL did not exhibitthis light scattering. On the basisof these observations, a hypothesis on the cause of the light scattering in the SCL state is proposed inrelation to structural transformation between different SCL states. A microscopic mechanism of the formation of ahigh-density glass with Vm smaller than that of SCL isbrieflydiscussed by referring to the observations of toluene samples which showed a slightlydifferent Td dependence of Vm and did not show the curious light scattering in the SCL state. © 2009 The Chemical Society of Japan.