Highly stretchable gamma-irradiated poly (vinyl alcohol)/Tannic acid composite hydrogels with superior transparency and antibacterial activity

The development of facile and cost-effective strategies for hydrogels with multifunctionality is of great scientific interest. In this work, a series of poly (vinyl alcohol)/tannic acid (PVA/TA) composite hydrogels were facilely prepared by gamma radiation of a PVA solution and subsequent soaking treatment in TA solutions. The chemical composition, transparency, microstructure, mechanical property and antibacterial activity of the resulting composite hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectroscopy, SEM, tensile measurements and an antibacterial test, respectively. The introduction of TA into the gamma radiation-induced chemically cross-linked networks of PVA hydrogels via the soaking treatment, which forms the second physically cross-linked networks, endows the PVA hydrogels with improved mechanical performance. The tensile strength, toughness and elongation at break of the composite hydrogel were increased by 1500 % (from 18 kPa to 254 kPa), 3600 % (from 8.5 kJ m−3 to 315 kJ m−3) and 360 % (from 87 to 403 %), respectively. Meanwhile, high transparency of the neat irradiated PVA hydrogels was maintained in the obtained composite hydrogels (transmittance over 60 % at 660 nm). The strong hydrogen bonding interaction between PVA and TA within the networks serves as sacrificial bonds and suppresses the crystallinity of the PVA hydrogels. In addition, the composite hydrogels also possess superior antibacterial activity against both gram-negative and gram-positive bacteria. This work provided a simple approach for the construction of multifunctional hydrogels on large-scale preparation, thus would hopefully promote their applications in biomedicine, wound dressings and soft devices.