Sustainable, Reshapable Surfactant–Polyelectrolyte Plastics Employing Water as a Plasticizer

Natural polymers such as those present in foods contain abundant noncovalent intra- and intermolecular interactions, notably hydrogen bonds, which make them rigid when dry, but on exposure to water soften, due to disruption of these interactions. This softening process allows them to be reshaped. Food-derived materials, however, have limited practical use due to their high brittleness and gradual degradation. Nevertheless, inspired by such properties, surfactant-polyelectrolyte-based polymers that contain abundant ionic interactions and can be repeatedly reshaped using water as plasticizer are described. The polymers, on the basis of main chain anionic poly(styrene sulfonates) combined with phosphonium surfactant, are readily synthesized with well-defined lamellar domains through interfacial metathesis reactions. The polymers present typical stress-strain characteristics of plastics, and their modulus undergoes a decrease of ca. 3 orders of magnitude upon shear and stretch forces after plasticizing with water. Since recycling of plastics generally involves complicated and energy-intensive processes (that leads to the majority of plastics being land-filled or incinerated), it is envisaged that reshapable polymers, such as those described here, could reduce the amount of plastic waste as they can be remolded as and when required, thus reducing pollution and the depletion of resources, ultimately contributing to a more sustainable society.