Calorimetric glass transition of ultrathin poly(bisphenol A carbonate) films

Abstract

Specific heat spectroscopy in the frequency range from 1 Hz to 10³ Hz with a sensitivity of pJ K⁻¹ was employed to study the glass transition behavior of ultrathin poly(bisphenol A carbonate) (PBAC) films with thicknesses ranging from 192 nm down to 10 nm. The amplitude and the phase angle of the complex differential voltage as a measure of the complex heat capacity were obtained as a function of temperature at a given frequency simultaneously. Both spectra are used to determine the dynamic glass transition temperature as a function of both the frequency and the film thickness. As the main result no thickness dependence of the dynamic glass transition temperature was observed down to a film thickness of 10 nm within the experimental uncertainty of ±3 K. The obtained data were compared with literature results in detail.