fig2
Figure 2. SEM images (longitudinal section) for FT (A), FS (B), and DFS PVA hydrogels with stretching ratios of 1 (C), 2 (D), 3 (E), and 4 (F) containing 15 wt% PVA. SEM: Scanning electron microscopy; FT: frozen-thawed; FS: frozen-salted out; DFS: directional freezing and salting-out; PVA: polyvinyl alcohol.
