3.4.1. Water Retention

In Table 3, there is a huge gap between the pure PU and PUSX nanofibers where the PU nanofibers showed the highest water retention of 280%, with statistical significance (*p* < 0.05).

Block-type PUSX nanofibers showed a decreasing trend in water retention with the increase of both silicone chain length and silicone concentration, because of the hydrophobicity of silicone. This also means that the water repellency of the PU nanofibers are able to be improved by introducing the silicone groups into the main chain. Meanwhile, compared with films, since nanofibers have a high porosity for holding water, the water retentions of the nanofibers are higher than films. Both the PU nanofibers and films have the highest water retentions. Higher hydrophobicity of silicone structure and moisture permeability were proven.

Meanwhile, for graft-type PUSX nanofibers, the silicone groups on the side-chain are not able to increase the hydrophobicity of the material, so that the water retention did not show any difference between the PU nanofibers and the graft-type PUSX nanofibers.


**Table 3.** Comparisons of water retention.
