Glass-transition temperature (Tg) of free-radically prepared polyacrylonitrile by inverse gas chromatography, 1 -: A study on Tg of atactic monodisperse polystyrenes

The glass-transition temperature (Tg) of several atactic monodisperse polystyrenes (PSt)s was studied by an inverse gas chromatographic (IGC) analysis, as a preliminary study for the detection of the Tg of polyacrylonitrile. The Tg of PSt with different molecular weights was clearly obtained by this method. The agreement in the Tg values obtained by IGC and by differential scanning calorimetry (DSC) was quite good within the molecular-weight range M̄p=7600-2 430 000 (where, M̄p=(M̄n × M̄w)1/2). This method has a wide universality for the detection of the Tg of polymers. Several essential factors were extracted for the establishment of the optimum conditions for IGC measurements, such as the concentration of polymer toward a clay matrix (10 Wt.-%), and the type of lower probe, decane. The best probe was determined empirically from the most effective detection in the IGC measurements of PSt.