Effect of solvent on surface wettability of electrospun polyphosphazene nanofibers

Two kinds of biodegradable polymers, poly(ε-caprolactone) (PCL) and poly[(alanino ethyl ester)₀.₆₇ (glycino ethyl ester)₀.₃₃ phosphazene] (PAGP), were electrospun by using four different solvents. All PCL nanofibrous mats had similar surface water contact angles independent of solvents. However, it was found that the water contact angles of PAGP nanofibrous mats were 102.2° ± 2.3°, 113.5° ± 2.2°, 115.8° ± 1.4°, and 119.1° ± 0.7°, respectively, when trifluoroethanol, chloroform, dichloromethane, and tetrahydrofuran were used as a solvent. This difference was supposed mainly due to phosphorous and nitrous atoms in PAGP being dragged to fiber surface with solvent evaporation during the solidification of nanofibers, because of the strong interaction between positive phosphorous atoms and electronegative atoms in solvents. This interaction was confirmed by Fourier Transform Infrared, and the accumulation of phosphorous and nitrous atoms in the solvent-casting PAGP film surface was identified by X-ray photoelectron spectrometry analysis. PCL samples did not show the solvent-controlled surface wettability because it contained fewer polar atoms.