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Wet and soft matter – as synthetic hydrogels – has attracted increasing interest in materials science community and significant breakthroughs have been made in the field, especially in terms of mechanical toughening. New gel designs with advanced mechanical responses suggest that gels could be key players in the development of emerging technologies as soft robotics, electronics or tissue engineering.

Conventional synthetic gels are mainly made of water – typically above 90% water – and behave like soft elastic solids. Polymer chains are organized into a percolating network at macroscopic scale with mesh sizes of the order of a few tens of nanometers. To prevent the fracture, one option consists of getting rid of material defects by designing ideal networks with a perfectly uniform mesh distribution. This results quite difficult and inefficient. We have adopted a different strategy, taking advantage of gel’s intrinsic fragility and introducing dynamic heterogeneities. Based on polymer physics principles, we have designed model systems that combine a conventional polymer network and the addition of weak reversible sacrificial interactions. Unlike conventional covalent bonds, these weak interactions having low selectivity can readily break and reform, ensuring topological adaptation under stretch. Working cooperatively, such reversible sacrificial bonds allow the gel to combine paradoxical properties, as enhanced rigidity and shape recovery together with self-repair abilities. This concept of gel toughening by weak bonds extends to the gel adhesion and proposes bridges with living matter.

In a global context of preservation of the resources, gels could open tracks for the design of sober and efficient synthetic materials.


Alba Marcellan is associate professor at Sorbonne University and she carries out her research at the Soft Matter Sciences and Engineering Laboratory at ESPCI Paris. She is currently member of the Global Station for Soft Matter at Hokkaido University in Japan.

Initially with a background in materials and mechanics (Mines Paris, Department of Materials Science and Engineering), her integration at ESPCI Paris broadened her interests towards Chemistry and Soft Matter. For over the last ten years, she has aspired to provide contributions in the field of materials science with a special interest in the impact of reversible sacrificial interactions on the deformation and fracture (bulk and adhesion) processes involved in polymer-based materials or assemblies. Her current research focuses on fibrous materials, focusing on the effects of cooperativity, and on the design of tough hydrogels. Her research topics can best be summarized as the “design of sober materials and assemblies with advanced mechanical responses”. Her approach is to favor efficiency rather than complexity, i.e. mechanical reinforcement efficiency with sober design rather than extremely high-performances with complex chemistries or involving large amounts of solvent. She was awarded by the French Polymer Society in 2015 and she joined the Institut Universitaire de France since 2017.

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