Fig. 1. （a~c）Digital photos of films making，iodine dyeing and hygrothermal aging；（d）Schematic diagram of polarizing films preparation.

Fig. 2. Single-chip transmittance of uncrosslinking（a）and crosslinking（b）polarizing films；Single-chip transmittance of uncrosslinking（c）and crosslinking（d）polarizing films after 3 h aging in hygrothermal environment.

Fig. 3. Changing curves of polarization degree of uncrosslinking（a）and crosslinking（b）polarized films；Changing curves of polarization degree of uncrosslinking（c）and crosslinking（d）polarizing films after hygrothermal aging.

Fig. 4. （a）Raman spectra of PVA polarizing films with different polymerization degree；（b）Schematic diagram of iodide ions in the lattice of polarizing films.

Fig. 5. XRD of polarizing films with different polymerization degree before and after agin.

Fig. 6. （a）FT-IR of PVA polarizing films；（b）FT-IR of PVA polarizing films before and after hygrothermal aging.

Fig. 7. Reaction diagram of crosslinking and hydrolysis of boric acid