We ini ally imaged the pure PVPVA and RTV films (0% and 100% drug loadings, respec vely) as a func on of buffer exposure me. Figure shows the me-lapsed images of a neat PVPVA film before and a er buffer addi on (right), together with (semi-)quan ta ve analyses of the components from the corresponding imaged areas (le ). Ini al qualita ve interpreta on of the CLS false color images (right), revealed that the film prior to buffer addi on (0 min) had a sharp, clear interface between the homogenous PVPVA (green) and air (black, due to the sole presence of air). Upon buffer addi on (cyan), polymer-buffer mixing was rapid and extensive, and the original interface disappeared already within 30 s. At this me point, the polymer signal (green color) dominated at the greatest depth in the film (bo om le corner of the image) and this gradually gave way to intense buffer signal (cyan) on the other side of the original interface (top-right corner of the image). The color became greener and more homogeneous in the imaged area over the next 5 min, indica ng increased homogeneity with increasing PVPVA content, consistent with dissolu on and diffusion of the polymer in the buffer.