Degradable, Recyclable, Water-Resistant, and Eco-Friendly Poly(vinyl alcohol)-Based Supramolecular Plastics

It remains a formidable challenge to fabricate degradable plastics that are recyclable, easy for processing and safe for use in seawater. In this study, poly(vinyl alcohol) (PVA)-based supramolecular plastics capable of degrading in soil and recycling under mild conditions are fabricated by grafting 4-carboxybenzaldehyde (CBA) onto PVA chains (hereafter denoted as PVA-CBA). The PVA-CBA plastics are dynamically cross-linked with a high density of hydrogen bonds and hydrogen-bond-cross-linked hydrophobic domains. The PVA-CBA plastics exhibit a yield strength of ∼84 MPa, which remains to be ∼40 MPa when the plastic is fully immersed in water. The satisfactory mechanical strength of the PVA-CBA plastics in watery environment originates from the hydrogen-bond-cross-linked hydrophobic domains comprised of CBA groups connected with PVA segments. Benefiting from the reversibility of hydrogen bonds, the PVA-CBA plastics can be conveniently processed to obtain products of desired shapes and are also recyclable under mild conditions for repeated usage. Importantly, the PVA-CBA plastics are autonomously and completely degradable in soil. In seawater, the PVA-CBA plastics can rapidly fragment into extremely soft, tiny and nontoxic hydrogel pieces that are safe to marine animals. Moreover, the PVA-CBA plastic bags can preserve the freshness of fruit much better than polyethylene bags.