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Electrospun poly(ε-caprolactone) (PCL) nanofibers are promising materials for biomedical applications due to their biocompatibility and biodegradability. PCL is a semicrystalline polymer, and its functional properties are strongly influenced by its crystalline-amorphous morphology. While the crystalline and amorphous domains are commonly distinguished, recent studies on multiphase polymers suggest that the amorphous region can be further subdivided into rigid and mobile fractions. The so-called rigid amorphous phase (RAP) is typically located near the crystallite boundaries, where chain mobility is significantly restricted, while the mobile amorphous phase (MAP) retains high segmental mobility. In this study, we applied modulated differential scanning calorimetry (MDSC) to quantify the crystalline, RAP, and MAP fractions in electrospun PCL nanofibers. Although the three-phase model is known in filled polymers, i.e. polymers containing reinforcing or functional fillers, its application to nanofibrous systems has not been explored so far. Nanofibers were electrospun from 16 wt% PCL solution in chloroform:ethanol (8:2 wt), and multiple MDSC runs confirmed the reproducibility of phase separation. The crystalline fraction appeared as the most dominant phase, while both amorphous fractions were also clearly distinguishable. The phase proportions exhibited only minor variation across repeated measurements, supporting the robustness and reproducibility of the method. Since degradation behavior depends strongly on amorphous mobility, this approach may aid in designing resorbable nanofibrous scaffolds with tailored properties and controlled mechanical performance (e.g., tensile strength).
Keywords: Poly(ε-caprolactone; electrospun nanofibers; morphology; molecular mobility© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.