Nacre-like composites with a soft thermoplastic elastomer matrix

We produce nacre-like composites made of a soft thermoplastic elastomer matrix reinforced by alumina platelets, as a flexible and healable alternative to stiff brick-and-mortar materials while keeping their characteristic anisotropic microstructure. Materials are manufactured using step-wise deposition and subsequent controlled evaporation of a suspension containing the polymer and the platelets. Well-aligned microstructures loaded from 15 to 65 vol.% in alumina are obtained through hot-pressing densification of the resulting composites. Remarkably, by combining calorimetry and low-field nuclear magnetic resonance, we emphasize that the polymer mobility decreases significantly in spite of a lower degree of cristallinity when the platelet content is increased. This result sheds light on the origin of the limited quality of samples above 45 vol.%, opening new research directions to improve the design of organic nacre-like composites. Tensile, bending and indentation tests on samples containing up to 45 vol.% in platelets are then used to rationalize the mechanical properties variation related to the polymer state. Finally, we show that the addition of 3 vol.% of Fe nanoparticles into the composites is enough to enable their induction heating that we aim to utilize in the future as a contactless healing method.