Vapor-deposited α,α,β-tris-naphthylbenzene glasses with low heat capacity and high kinetic stability

Abstract

The reversing heat capacity of vapor-deposited glasses of α,α,β-tris-naphthylbenzene (ααβ-TNB) was measured using alternating current (AC) nanocalorimetry. Glasses deposited at 0.85 T(g), where T(g) is the glass transition temperature, have a 4 ± 1% lower heat capacity than the ordinary glass prepared by cooling from the liquid. This is a result of efficient packing and is consistent with the higher density of the vapor-deposited glass. Isothermal experiments show that vapor-deposited ααβ-TNB glasses also have enhanced kinetic stability with respect to transformation into the supercooled liquid, as expected from previous work, with transformation times approaching 10(5) times the structural relaxation time of the liquid. Films thinner than 1 μm exhibit a thickness dependence to their transformation times that is consistent with transformation to the supercooled liquid via a surface-initiated growth front.