The A₄ glass transition singularity

Formulae for the β-relaxation process as obtained within the mode coupling theory for the dynamics of supercooled liquids are derived for states near an A₄ glass transition singularity. A discussion of the expected anomalies of susceptibility spectra is presented. In particular the parameter regions for (1/f)-noise, for spectra exhibiting two minima and regions of linear variations in ln(1/f) are identified. The results are used to interprete quantitatively dielectric data for the following polymeric systems: polychlorotrifluoroethylene (PCTFE), polyhexamethylene sebacamide (nylon 610), polyoxymethylene (delrin) and polyparaethylene oxybenzoate (PEOB).