(2) motions requiring a large amount of free volume and/or intermolecular activation energy for the α-relaxation processes. In the case of the low, medium, and high MW materials of PLGA 50:50 and PLGA 75:25 the change in absorption with temperature can be observed to take place over three distinct Table : Gradient, m, of the linear fit (y = mx + c) for the respective temperature regions as outlined in Section as well as the respective glass transition temperatures determined based on the terahertz analysis. For high MW PLGA 50:50 and PLGA 75:25 only two regions were identified using the data analysis routine, r = 2, whilst for all other samples three regions were found, r = 3. regions and two transition temperatures, T g,β and T g,β , as determined using the methodology outlined above (see Figures and; Figures and; and Table ). In the case of PDLLA again three distinct regions with two transition temperatures are apparent (Figure ).