A Highly Stretchable and Superhydrophobic Electrospun Fiber Made of Fluoroalkylsilane-Modified SEBS- <i>g</i> -MA Incorporating Functionalized Silica Nanoparticles

Materials that are simultaneously superhydrophobic and highly stretchable offer great potential for wearable electronics and biomedical applications. However, achieving both superhydrophobicity and stretchability is a challenge due to deterioration of the strained surface. In this study, we report the fabrication of highly stretchable and superhydrophobic electrospun fibers based on fluoroalkylsilane (FAS)-modified polystyrene-<i>block</i>-poly(ethylene-<i>ran</i>-butylene)-<i>block</i>-polystyrene-<i>graft</i>-maleic anhydride (SEBS-<i>g</i>-MA) elastomers, incorporating functionalized silica nanoparticles (F-SiNPs). Silica nanoparticles were chemically modified to contain epoxide groups on their outer interfaces to form F-SiNPs. The maleic anhydride groups of SEBS-<i>g</i>-MA reacted with the epoxide groups on the F-SiNPs, facilitating covalent grafting of the F-SiNPs to the polymer. Then, SEBS-<i>g</i>-MA/F-SiNP composite fibers were prepared via electrospinning, followed by FAS surface treatment to enhance their hydrophobicity. The presence of F-SiNPs in the fibers significantly improved both the mechanical stretchability and surface roughness of the fibers, while the FAS coating further promoted their hydrophobicity. Fourier transform infrared (FT-IR) characterization confirmed the successful incorporation of F-SiNPs and FAS molecules. The Young's modulus of the fibrous mat, after the incorporation of F-SiNPs, showed a 1.37-fold increase, indicating an increase in mechanical stiffness. SEM analysis revealed that the modified fibers retained their morphology under high tensile strain (up to 800%). In addition, contact and sliding angle values demonstrated superhydrophobic behavior, with contact angle values exceeding 150° and sliding angle values remaining under 10°, even under repeated mechanical strain over 1,000 times. This dual functionality of high stretchability and superhydrophobicity highlights the potential of these fibers in next-generation flexible electronics, strain sensors, and wearable and implantable biomedical devices where both durability and resistance to environmental stress are critical.