If we consider the macromolecules of amorphous PLGA as a covalently linked assembly of mobile segments where each segment has an associated degree of free movement, the interlacing chains of random molecular arrangement will result in free volume (which is essentially the surplus empty space or voids between the copolymer chains). With increasing free volume the potential energy barriers for the chain segments to change in dihedral angle decrease further, and a wide range of local motions become possible (resulting in the βrelaxation process). Ultimately, the α-relaxation sets in when sufficient free volume and thermal energy is available, for the large amplitude motions of the intermolecular chains.