The equivalent 100% RTV film me-lapsed images are shown in Figure . The dry film (0 min) was evenly magenta, and there was a sharp matrix-buffer interface, in a similar fashion to that observed for the polymer film. A er addi on of the buffer, in stark contrast to the PVPVA film, the RTV film appeared largely inert for the dura on of the experiment, with the interface remaining at virtually the same posi on (now represen ng the RTV-buffer interface). The coefficient values of RTV and buffer were almost completely separate (most of the overlap can be a ributed to an uneven interface, already evident from the RTV coefficient values at 0 min) and essen ally unchanged for the en re imaging me (up to 30 min), indica ng minimal mixing and dissolu on of RTV. A very slight shi of the interface to the right at the la er me points suggests some very limited RTV film swelling (Figure ). Correla ve SFG analysis a er 30 min addi onally confirmed that the RTV remained amorphous (as evidenced through the absence of SFG signal, data not shown), consistent with previously published analyses of amorphous RTV a er immersion in pH 6.8 buffer, as determined by ex situ Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) .