Effect of surface interactions on the glass transition temperature behavior of amorphous polystyrene

The glass transition temperatures (Tg) of nanosized thin polystyrene (PS) films were determined using FTIR (or, more specifically, the absorbance peak at 797 cm−1). This novel method was used to verify the presence of surface interactions between polymer and substrate. As surface interactions may lead to changes in Tg, various amounts of nanoparticles of TiO2 and of ZnSe were uniformly deposited on the surface of free-standing PS film to simulate increases in surface interactions. FTIR spectra of thin PS films coated with various amounts of these nanoparticles were recorded as a function of temperature, and the Tg values obtained using this method were compared to results obtained using conventional differential scanning calorimetry (DSC). The addition of TiO2 nanoparticles leads to an increase in Tg, while the addition of ZnSe depresses the glass transition temperature. Both effects are linear with respect to the amount of nanoparticles. These results support the argument that increasing surface interactions leads to changes in chain mobility, as determined from variations in Tg.