Poly(vinyl alcohol)–Tannic Acid Hydrogels with Excellent Mechanical Properties and Shape Memory Behaviors

Abstract

Shape memory hydrogels have promising applications in a wide variety of fields. Here we report the facile fabrication of a novel type of shape memory hydrogels physically cross-linked with both stronger and weaker hydrogen bonding (H-bonding). Strong multiple H-bonding formed between poly(vinyl alcohol) (PVA) and tannic acid (TA) leads to their coagulation when they are physically mixed at an elevated temperature and easy gelation at room temperature. The amorphous structure and strong H-bonding endow the PVA-TA hydrogels with excellent mechanical properties, as indicated by their high tensile strengths (up to 2.88 MPa) and high elongations (up to 1100%). The stronger H-bonding between PVA and TA functions as the "permanent" cross-link and the weaker H-bonding between PVA chains as the "temporary" cross-link. The reversible breakage and formation of the weaker H-bonding imparts the PVA-TA hydrogels with excellent temperature-responsive shape memory. Wet and dried hydrogel samples with a deformed or elongated shape can recover to their original shapes when immersed in 60 °C water in a few seconds or at 125 °C in about 2.5 min, respectively.

A Flexible Stretchable Hydrogel Electrolyte for Healable All‐in‐One Configured Supercapacitors

“…The physically crosslinked PVA‐H 2 SO 4 hydrogel was prepared with enormous hydrogen bonds. The crystal region was formed by freezing, which works as the crosslinked points for connecting various random PVA polymer chains to retain the 3D network structure (Figure S2, Supporting Information) . Under mechanical deformation, the mechanical strength could be effectively distributed by the crosslinked points, demonstrating the excellent mechanical strength.…”

Synthesis of bio‐based internal and external cross‐linkers based on tannic acid for preparation of antibacterial superabsorbents

“…It should be considered that fully TA‐based hydrogels are brittle in nature with low swelling degree; this indicates the need for using TA along with other monomers . Therefore, TA was applied as hydrogen bonding cross‐linker along with chitosan, gelatin, collagen, Arabic gum, DNA, polyvinyl alcohol, and poly( N ‐isopropylacrylamide) …”

Quadruple hydrogen bonding containing supramolecular thermoplastic elastomers: Mechanical and morphological correlations

“…Adenine and thymine derivatives in particular are widely incorporated into synthetic polymers because of their availability and facile functionalization strategies . Self‐association and complementary association between nucleobases serve as physical crosslinks, which enhance physical properties of polymers and provide thermal or solvent reversibility . For example, Long and coworkers synthesized acrylic ABA triblock copolymers containing adenine or thymine pendant groups in the external blocks, and this work demonstrated that complementary hydrogen bonding enhanced thermomechanical properties and melt processability .…”