Biobased PEF/PLA Bilayer Electrospun Films with Enhanced Mechanical, Barrier, and UV-Protective Properties.

Poly-(lactic acid) (PLA) electrospun films are attractive for biomedical and packaging uses, but they are brittle and provide weak UV protection. Poly-(ethylene furanoate) (PEF) is biobased and offers excellent barrier properties but limited ductility. We fabricated PEF/PLA bilayer electrospun films in which curcumin-loaded PLA serves as the active top layer and PEF acts as a mechanically supportive, barrier, and photoprotective backing. Sequential electrospinning was adopted after identifying hexafluoro-2-propanol (HFIP) as a suitable PEF solvent that yields strong adhesion, whereas trifluoroacetic acid (TFA) produced unstable interfaces. Bilayers showed smaller, more uniform fibers, significant interfacial cohesion, and mechanical gains compared with a PLA monolayer, including higher tensile strength, elongation, and modulus. FTIR indicated no new covalent bonds on curcumin addition, consistent with mainly physical interactions. Increasing curcumin content lowered contact angle, tuned hydration, and modulated release: 1-2 wt % enabled slow, sustained delivery (∼20% at 9 h), whereas 3 wt % accelerated release (∼50% at 9 h) due to morphology-related effects. Water-vapor permeability was high initially but decreased markedly over 72 h as the fibrous network equilibrated. Orientation-dependent UV tests showed that the PEF layer effectively shielded the curcumin-loaded PLA from UV-A, while direct exposure of the PLA side caused measurable degradation. This structurally engineered, biobased bilayer couples mechanical reinforcement, barrier and UV-shielding with controllable payload release, supporting sustainable films for biomedical, food packaging, and other protective applications.