Influence of spin coating parameters on the fabrication of free standing porous and nonporous poly(ε-caprolactone) based films

Spin coating is a widely used technique for producing uniform thin films with controlled thickness; however, its use in fabricating free-standing and porous films remains relatively underexplored. This study reports the successful fabrication of free-standing biodegradable PCL and PCL/PEO (50/50) blend films via spin coating by varying polymer concentration, spin speed, and the number of spinning cycles. The resulting films exhibited uniform thicknesses ranging from 15 to 141 μm for PCL and 24-228 μm for the PCL/PEO blends, with a milky, translucent appearance and occasional macroscopic dendritic structures. The incorporation of PEO increased the solution viscosity, leading to thicker films. SEM imaging revealed diverse surface morphologies, including spherulites, phase-separated PEO-rich protrusions, worm-like structures, and micropores. XRD analysis confirmed the crystalline structures of both PCL and PEO, with reduced peak intensities at higher polymer concentrations and spin speeds, suggesting increased lattice imperfections and amorphization. Selective leaching of PEO yielded white, opaque, and porous PCL films with thicknesses ranging from 8 to 90 μm and an average porosity of 47%. Water uptake ranged from 86 to 196%, correlating with film thickness and pore structure. XRD analysis confirmed complete removal of PEO while preserving the crystalline structure of PCL. Optimal porous morphologies were achieved at a polymer concentration of 160 mg/ml, with a spin speed of 6000 rpm further enhancing crystallinity. These tunable PCL-based films show promise for applications in biodegradable scaffolds, wound dressings, drug delivery systems, and filtration.