The FTIR spectra of the copolymers before and after degradation study are shown in Figure and only slight changes in band's intensity of copolymers can be seen. The observed diferences appeared in the C-O and C-C stretching in a spectral range from 1000 cm -1 to 1500 cm -1 . There are also two regions highlighted in Figure , where region 1 represents the absorbance of methylene -CH2stretching groups of the aliphatic soft segments (bands at 2853 cm -1 and 2920 cm -1 ), and region 2 shows the absorbance of carbonyl C=O bond stretching, which is represented by a peak at 1718 cm -1 . According to the data presented in Figure region 1 (-CH2-region), there is an increase in the absorbance of the bands at 2853 cm -1 and 2920 cm -1 after the degradation. It is already known from the literature that PBS is a degradable polymer that undergoes erosion during degradation . This has been confirmed by both experimental findings, including our previous studies , and theoretical models that predict erosion mechanisms in water- insoluble biodegradable polymers . This comprehensive model, incorporating parameters such as water diffusivity, degradation rates of polymer functional groups, and matrix dimensions, suggests that degradable polymers experience either surface erosion or bulk erosion depending on specific conditions. In previous enzymatic degradation study of PBS-DLS copolymers, where a surface erosion mechanism was identified , similar changes were reported in FTIR data for materials discussed in this work.