Mechanically Strong Polyelectrolyte Complex Plastics: Salt-Free Processing, Self-Healing, and Recycling Based on Super Hydroplasticity

Polyelectrolyte complexes (PECs) represent a wide class of materials with many applications such as functional biomaterials, coatings, adhesives, and plastic substitutes. However, solution-precipitated PECs are considered extremely difficult to process because of the infusibility and insolubility. Current processing approaches usually require substantial salts as plasticizers, which affect the intrinsic properties and complicate the processing steps. Herein, we show that a variety of PECs that contain highly hygroscopic natural-derived polyelectrolytes can be facilely manufactured via rolling and extrusion processes with the aid of water, which acts as a sustainable and traceless plasticizer. These hydroplastics formed by renewable polysaccharides of sodium alginate (SA) and chitosan quaternary ammonium salt (QCS) exhibit high mechanical strength with a tensile strength of ≈58 MPa and Young’s modulus of ≈5.8 GPa when dry, which are comparable to many common high-performance petrochemical plastics. The wetted SA-QCS shows super hydroplasticity, which permits easy self-healing and reprocessing through the water-facilitated reconstruction of ionic bonds and rearrangement of polymer chains. These hydroplastics show great advantages in enzyme immobilization owing to mild processing and excellent biocompatibility. We expect this work to open a new vista in the study of solid PECs materials and in the design of functional hydroplastics.