In order to verify the effect of enzymatic degradation of new PBS-DLS-PEG copolymers on their crystalline morphology we observed their microstructure with the polarized light microscopy. Polymeric samples crystallized from the melt showing crystalline structure before and after the enzymatic degradation are presented in Figures and. The structural features of the crystallized copolymers are spherulites typical for semicrystalline polymers. The formation of the spherulites began with the emergence of nucleated crystalline domains, which grew radially and had a fibrillar texture . All samples revealed characteristic spherulites differing in size depending on segmental composition. Before the degradation, ring-banded spherulites indicating the twisting of lamellae were observed, with remarkable size difference depending on the segmental ratio, so that the copolymers with higher hard segment content (70 wt.%) showed large and well organized ring-banded spherulites with an average size of 142 µm (Figure ), while the copolymers with lower amount of hard segments (60 wt.%) (Figure ) showed smaller ring-banded spherulites (58µm). These results are consistent with (but not limited to) the relationship of the hard segments content and the degree of crystallinity. As demonstrated by the DSC cooling thermograms (Figure ), the copolymers with a higher hard segment content (70 wt.%) have been found to have the degree of crystallinity, Xc= 42% before the degradation, while those with a lower percentage of hard segments (60 wt.%) tend to have the degree of crystallinity Xc= 36%. After 20 days of degradation, the amount of crystalline phase in polymer with the smallest spherulites (58µm) has been reduced to Xc= 26.3%. The formation of ring-banded spherulites was often observed in various polyesters, such as poly(ethylene adipate) (PEA), poly(butylene adipate) (PBA), and poly(trimethylene terephthalate) (PTT) - , and also in a wide range of semicrystalline polymer systems, such as PCL and poly(3-hydroxybutyrate) (PHB) , . Changes in polymer morphology are related not only to the degree of crystallinity but also to water diffusion since material with high crystallinity restricts the diffusion of water molecules . In semicrystalline polymers, the banded-spherulites have two regions: the crystalline lamellae and the amorphous tie chain regions, where the diffusion of water molecules is more restricted in crystalline lamellae. This means that water molecules have an easier ability to move through the amorphous regions and break down the bonds. Addition of PEG in copolymers of both segmental compositions resulted in formation of larger spherulites (Figure and figure ), because of the contribution of the crystalline phase of PEG on the copolymers morphology . This was also observed after the degradation study, that the average size of the spherulites of the copolymers with 70% of hard segment, increased from 155µm to 253µm by addition of the PEG (