Investigation of α-PVA/s-PVA Hydrogels Prepared by Freezing-thawing Method

摘要

The hydrogels of atactic poly (vinyl alcohol) (a-PVA) and syndiotactic poly (vinyl alcohol) (s-PVA) with different blend ratios were prepared by freezing-thawing processes. The effect of s-PVA on gelation behavior of the blend was investigated in terms of gelation temperature (r_(gel)) and hydrogel melting temperature (T_m). And swelling behavior, crystallization, thermal properties, morphology of the blend hydrogels were also studied. With the increase of s-PVA, T_(gel) of the blend solution and T_m of the blend hydrogels increase. Both crystallinity and crystallite dimensions based on the XRD profiles are nearly monotonically increasing functions of s-PVA content. FTIR results indicate the number of hydrogen bonds raises with s-PVA increasing. DSC results demonstrate s-PVA favors improvement of hydrogels thermal stability. According to SEM images of hydrogels, the increase of cross-linking caused by s-PVA in the blend hydrogels results in denser structure, which in turn leads to increased gel fraction (G) and Hardness. 50/50 (α-PVA/s-PVA) blend hydrogel has a denser structure with EWC of 73.6 %, hardness of 22.8 HA and Tm of 236.15 °C. The result indicates blending a-PVA and s-PVA is a useful method to form the hydrogel having good thermal stability and relative high degree of swelling.