The C CP MAS NMR spectrum with a short contact time of 0.2 ms displays mostly resonances of crystalline segments, which in case of the investigated PCL results in the appearance of two resonances in the carbonyl region. The resonance at 173.8 ppm is observed in the starting material as well, whereas the additional resonance at 174.7 ppm was newly observed after the catalytic reaction. Notably, we conclude that the newly formed HA units become part of the (co)crystal. Direct polarization (DP) excitation with a short recycle delay of 1 s was used to detect resonances of the highly mobile, amorphous components in the C MAS NMR spectrum, which displays only one resonance at 173.2 ppm that appeared as a shoulder in the C CP NMR spectrum with 2 ms contact time. Assuming that the small resonances close to the major carbonyl resonance at 172.21 ppm in the solution C NMR spectrum are not resolved in the solid-state C NMR spectra, we assigned the new additional resonance at 174.7 ppm after catalysis to the newly formed HA units, which are thus found to represents the second major species in crystalline segments.