*2.4. Characterization of the PVDF Composite Nanofibers*

The morphology of the PVDF composite nanofibers was visualized by scanning electron microscopy (SEM, S-4300, Hitachi, Japan) at an acceleration voltage of 5 kV after sputter coating of samples with gold. Image-Pro Plus software (Media Cybernetics Inc., Rockville, MD, USA) was used to determine the average fiber diameters for the composite nanofibers. Energy dispersive spectroscopy (EDS) spectra were obtained for the determination of the distribution profile of the POSS–EGCG conjugate on the nanofiber surface.

Fourier transform infrared spectroscopy (FTIR) measurement was performed using an ALPHA spectrometer (Bruker OpticsBillerica, MA, USA) with a resolution of 4 cm−1. Attenuated total reflectance (ATR) mode was used to analysis the characteristic bands over a range from 400 to

1600 cm−1. The relative β-phase content (F(β)) in the samples was determined from the following equation [29].

$$\mathbf{F}(\boldsymbol{\beta}) = \frac{\mathbf{A}\_{\beta}}{\left(\frac{\mathbf{K}\_{\beta}}{\mathbf{K}\_{\alpha}}\right)\mathbf{A}\_{\alpha} + \mathbf{A}\_{\beta}}$$

where A<sup>α</sup> and A<sup>β</sup> represent the absorbance of peaks related to the α- and β-phases at 760 and 840 cm<sup>−</sup>1, respectively, and Kα and Kβ are the absorption coefficients at the respective wavenumbers, which are 7.7 × 104 cm2/mol and 6.1 × <sup>10</sup><sup>4</sup> cm2/mol.

X-ray diffraction (XRD) patterns were also used to evaluate the crystalline phases of the PVDF composite nanofibers and thus XRD measurements were performed using a Rigaku D/MAX-2500V/PC X-ray diffractometer (Japan) with high intensity Cu Kα radiation at 40 kV/100 mA. The diffractograms were scanned in a 2θ range from 10◦ to 50◦. The composite nanofiber samples were analyzed using X-ray photoelectron spectroscopy (XPS) to obtain the surface elemental composition. XPS measurements were performed using a Quantera SXM (ULVAC-PHI Inc., Japan) equipped with a monochromatic Al Kα X-ray source (1486 eV). The photoelectron take-off angle was fixed at 45◦ relative to the sample surface. Besides XPS measurements, static contact angles were measured with a DSA 100 contact angle meter (KRÜSS, Germany) to examine the hydrophobicity of the composite nanofiber. Each contact angle of the sample is an average of five measurements. The mechanical properties of the composite nanofibers were investigated with a TO-101 universal testing machine (Testone Co., Siheung, South Korea) with 2 kN load capacity at a rate of 10 mm/min. All samples were cut into rectangular specimens with a size of 3 cm × 1 cm and tested five parallel measurements.
