Previous studies have shown that tannic acid (TA), which is responsible for the astringency of tea, forms a gel simply by mixing it with polyethylene glycol (PEG) [also known as polyethylene oxide (PEO)] in water [Kimetal., Adv. Funct. Mater.], the research group experimented with ultra-high molecular weight PEG (PEO) (molecular weight 50).As a result, when TA was mixed with water, a rubber-like gel was obtained that was completely different from the previously reported TA/PEG gel.This gel was named TaPeO gel and its properties were investigated.

　As a result, it was found that the TaPeO gel stretched well when it was pulled in a wet state, showing a maximum elongation rate of 1,000%. The TaPeO gel turned into a lightweight and tough plastic-like material when dried.

　In addition, even if the dried TaPeO gel was broken, the broken surface was immersed in hot water and re-adhered, and then it was restored.Although the dried TaPeO gel itself is a hard material, it can be deformed by immersing it in hot water and applying stress.When the deformed material was immersed in hot water again, it returned to its original shape.

　Furthermore, when the unnecessary supernatant generated during TaPeO gel preparation was dried without being discarded, a highly stretchable film (TaPeO film) with an elongation rate of over 1,500% could be prepared.That is, using TA and PEO, we were able to prepare strong and clever gels and films with “zero waste”.

　Tannic acid is a cheap, safe, and environmentally friendly material.In addition, it has antibacterial and antiviral effects, and antiviral effects against the new coronavirus have been reported.In the future, we plan to make effective use of such knowledge and apply it to medical materials.

Paper information:[Results in Materials] Zero-Waste Preparation of Supramolecular Hydrogels and Films Comprising Tannic Acid and Ultra-High-Molecular-Weight Polyethylene Oxide