Tardigrade inspired polyelectrolyte complexation and functional materials

Abstract

Cryptobiosis and modulated macromolecular assembly at dynamic water–ice interfaces are crucial to Tardigrades' survival at extremely low temperature. This inspires the shape memory assembly of oppositely charged polyelectrolytes upon dynamic phase changes spanning water freezing temperatures, in stark contrast to conventional polymer self-assembly that mainly occurs in solution. A weak polyanion and a polycation were mixed in dimethyl sulphoxide and sprayed into liquid nitrogen. Frozen microparticles were transferred to an ethanol–ammonia solution, whereby polyelectrolyte complexation was simultaneously coupled to particle thawing to retain particle shapes. It represents a versatile method to process insoluble polyelectrolyte complexes (PECs), as further demonstrated by the preparation of PEC microcapsules, porous monoliths and hybrid membranes. This work represents a paradigm shift of macromolecular assembly from solution to freeze-thawed dynamic interfaces, opening doors to progressive polyelectrolyte complexation for energy and environmental applications as exemplified here by solar thermal desalination membranes.