Optimization of PVP/PCL nanofiber diameter using coaxial electrospinning: response surface methodology and physicochemical characterization

• Optimization of coaxial electrospinning using Response Surface Methodology • PCL, PVP, voltage, and distance significantly affect fiber diameter and morphology • Optimal conditions yielded uniform solid nanofibers with ∼526 nm diameter • Mechanical tests showed PVP reduces strength but improves hydrophobicity • FTIR and XRD confirmed hydrogen bonding and semicrystalline nanofiber structure The electrospinning process offers a versatile platform for fabricating polymer-based nanofibers; however, precise parameter optimization is essential to achieve desirable morphology and performance. This study focuses on optimizing the coaxial electrospinning parameters for PCL/PVP nanofiber fabrication using Response Surface Methodology (RSM). A quadratic regression model was established to assess the combined effects of PCL concentration (10–15% w/v), PVP concentration (10–15% w/v), collector distance (120–160 mm), and applied voltage (12–20 kV) on nanofiber diameter. Statistical analysis confirmed the model’s robustness and predictive accuracy (p < 0.0001; R² = 0.9995; Adjusted R² = 0.9990; Predicted R² = 0.9983). The optimized condition yielded nanofibers with an average diameter of 526 nm and uniform morphology. Mechanical characterization indicated balanced tensile properties (tensile strength ∼10 MPa; elongation at break ∼5%; Young’s modulus 49–51 MPa), while surface wettability tests revealed improved hydrophilicity with a water contact angle of 70–79°. FTIR analysis identified intermolecular hydrogen bonding between PCL and PVP, and XRD confirmed a semi-crystalline structure with crystallinity of 33–37%. The findings demonstrate that RSM is an effective statistical tool for process optimization in coaxial electrospinning, enabling systematic control over nanofiber morphology and performance. This optimized approach provides a reliable framework for designing composite nanofibers with tunable structural and physicochemical properties, supporting their potential use in biomedical and materials engineering applications.