Surface and interfacial effect on polymer glass transition temperature studied by positron annihilation

Abstract Glass transition temperature ( T g ) as a function of depth and interfacial effect in polystyrene (PS) films is investigated by using positron annihilation spectroscopy (PAS) coupled with the slow positron beam technique. We report the results of the S parameter from Doppler broadening energy spectra as a function of temperature across T g in PS films of different thickness on Si substrate. The depression of T g as the film thickness decreases is consistent with the existing data. The use of PAS to study the surface and interfacial effect on polymeric properties is discussed.