In addi on to surface-oriented phase separa on, close inspec on of the SRS false color images (Figure ) reveals a second form of phase-separa on within the films, namely water-induced bulk phase separa on, which has previously been modelled in pharmaceu cal PVPVA ASDs in buffer . At the 20% drug loading, this manifests as the development of non-surface directed drug-rich (magenta) droplets within a con nuous polymer-rich (green) network, consistent with previous indirect observa on with confocal fluorescence microscopy involving fluorescent dyes , as well as thermodynamic perturbed-chain associa ng fluid theory (PC-SAFT) modelling . At 1 min, this is already observed in the SRS false color images on the microscale, with the phase separa on appearing to extend deeper and deeper into the matrix a er longer buffer exposure mes. This can also be observed to some extent at 1 min as very fine oscilla ons in the polymer and drug coefficients between -50 µm and the surface-directed phase separa on, and, as the domain sizes and concentra on gradients grow (from 2 min onwards), also as increased coefficient standard devia ons.