Fragility of a thermoplastic polymer. Influence of main chain rigidity in polycarbonate

We present new data on a vitreous polycarbonate (PC) and its fragility index. Measurements have been performed by means of differential scanning calorimetry (DSC). A comparison with other data already published in this field and concerning other linear polymers is made. We show that when experiments are performed by means of DSC, the use of the glass-forming liquid fragility concept does not lead to large enough variations of the fragility index values. Thus, any correlation with structural characteristics of linear polymers, is not possible, except in the case of main chain rigidity.