Swelling Resistance and Mechanical Performance of Physical Crosslink‐Based Poly(Vinyl Alcohol) Hydrogel Film with Various Molecular Weight

The present work aimed to develop polyvinyl alcohol (PVA) hydrogel films with physically crosslinking through controllable entanglement density of the polymer chains. The viscoelasticity of PVA aqueous solutions was investigated over a broad range in molecular weight. The chain length between the crosslinks in the hydrogel (Me¯) and entanglement density was determined by the plateau modulus (G'). The value of (Me¯) increased with the PVA molecular weight, which can be attributed to the enhanced entanglement associated with the hydrogen bonds between inter‐ and interchains. The melting and crystallization of the transparent PVA hydrogel films showed that the crystallinity was below 30%, which indicated that microcrystallites formed. Therefore, the entanglement effect and microcrystallization enhanced the stable crosslinked hydrogel network, which further improved by an increase in the molecular weight. Altogether, the PVA with the molecular weight higher than 88,000 g/mol can be envisioned as a promising material for preparing the hydrogel film possessing excellent performance. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1673–1683