Elastomeric PU-Pluronic F-127 Thin Films: Catalyst and Solvent Effects on Microstructure, Mechanical Properties, and Biocompatibility

While Pluronic F-127 is widely used to create hydrogels, this study investigates its novel application as a semicrystalline soft-segment within elastomeric polyurethane thin films. A series of elastomeric polyurethane-Pluronic F-127 (PU-PF) films was synthesized to investigate the influence of catalyst and solvent selection on the polymer thin film properties. A facile, low-hazard synthesis route using lactic acid as a catalyst and butyl acetate as a solvent (LA_BA) was identified as the optimal synthesis condition. Comprehensive characterization (X-ray diffraction (XRD), atomic force microscopy (AFM), Raman, and differential scanning calorimetry (DSC)) revealed the LA_BA film is a complex, microphase-separated copolymer with 29.29% quasi-crystallinity. The nanostructure consists of a soft, ordered PrePU hard-segment network (modulus ∼20-30 kPa) embedded with stiffer and dendritic Pluronic F-127 domains (∼150-350 kPa). This model, supported by broad XRD peaks and the absence of a melting endotherm (<i>T</i> _m), coexists with a highly mobile, plasticized amorphous phase (<i>T</i> _g = -45.04 °C). This unique microstructure was found to govern the film's high performance, affording both superior flexibility (990% elongation) and an oxygen transmission rate (OTR) that exceeded a commercial standard. Furthermore, <i>in vitro</i> assays confirmed the LA_BA film is noncytotoxic (ISO 10993-5 standard) and a nonirritant in a three-dimensional (3D) reconstructed human epidermis (RhE) model (OECD 439 standard). The combination of a low-hazard synthesis, a well-defined structure, robust performance, and demonstrated biocompatibility positions the LA_BA film as a strong candidate for advanced medical or cosmeceutical applications, such as wound dressings or transdermal patches.