Scaling behaviour in poly(propylene glycol) in the glass transition range

We have performed dynamic light-scattering experiments on poly(propylene-glycol) (PPG) above and below the glass transition temperature (200 K). In addition to the α-relaxation (stretched exponential decay with stretching parameter β_K ≈ 0.40), we observe two relaxation processes not witnessed before by photon correlation spectroscopy. They are attributed to the α′- and βrelaxations and they exhibit similar power law decays. All three processes are analysed in terms of recent mode coupling theories. The scaling relations inherent in the mode coupling approach are tested by determining the relevant exponents directly from the spectra.