Electrospun Poly(ϵ-caprolactone)/Polyhedral Oligomeric Silsesquioxane-Based Copolymer Blends: Evolution of Fiber Internal Structures

This study reports the structural transition of electrospun poly(ϵ-caprolactone) (PCL)/poly[(propylmethacryl-heptaisobutyl-polyhedral oligomeric silsesquioxane)-co-(methyl methacrylate)] (POSS-MMA) blends, from PCL-rich fibers, to bicontinuous PCL core/POSS-MMA shell fibers, to POSS-MMA-rich fibers with a discontinuous PCL inner phase. A ternary phase diagram depicting the electrospinnability of PCL/POSS-MMA solutions is constructed by evaluating the morphological features of fibers electrospun from solutions with various concentrations and PCL/POSS-MMA blend ratios. X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry are further used to characterize the electrospun PCL/POSS-MMA hybrid fibers. These physicochemical characterization results are thoroughly discussed to understand the internal structures of the hybrid fibers, which are directly correlated to the phase separation behavior of the electrospun solutions. The current study provides further insight into the complex phase behavior of POSS-copolymer-based systems, which hold great potential for a broad spectrum of biomedical applications.