Vibrational shifts between neat U and the PVC:U complex can also be observed and are between 3435-3440, 1615-1625, and 1594-1597 cm -1 . Such vibrational shifts are associated with U N-H bond stretching and bending. A 960-965 cm -1 shift between neat PVC and the PVC:U complex can also be identified. None of these shifts are visible in Figure for the 1:7 PVC:U physical mixture, so we can conclude that in the 1:7 complex PVC and U are interacting on a more intimate molecular level when solution processed as described here. Also note from Figures and that the U vibrational peaks below 1700 cm -1 are closely similar in neat U, the 1:7PVC:U complex, and the 1:7 PVC:U physical mixture. This is a result of the crystallization of the excess uncomplexed U in the 1:7 PVC complex. This observation is confirmed by DSC observations, as we shall see.