Post-Spinning Click Cross-Linked Biobased Polyurethane Coaxial Nanofibers

Two biobased thermoplastic polyurethanes with maleimide and thiol moieties (PU-MAL and PU-SH) were electrospun in a coaxial configuration and subsequently cross-linked across the interface via thiol-maleimide Michael addition to obtain homogeneous and nonsoluble nanofibers. PU-MAL and PU-SH were first synthesized using both solvent- and catalyst-free procedures and coelectrospun in a stoichiometric ratio as the core and sheath, respectively. Postspinning click reaction of the nanofibers led to tough membranes, exhibiting almost a 50% increase in Young's modulus and three times higher both tensile strength and elongation at break values. Clicked nanofibers of ∼350 nm in diameter presented a regular surface morphology, resistance to organic solvents, and enhanced hydrophobic character. Finally, a membrane containing an excess of thiol groups was electrospun to be, on the one hand, functionalized with 1H,1H,2H-perfluoro-1-decene to improve its hydrophobicity and, on the other hand, used as synthesized for the adsorption of silver nanoparticles from aqueous solutions. These results demonstrated that our proposal led to strong membranes with tailored characteristics, suitable for applications with solvent resistance, hydrophobicity, and adsorption requirements, such as wastewater treatment.