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Starch based materials with multi-shape memory properties

Starch-based polymers and bio-nanocomposites are an innovative and relevant topic in the field of “Green Chemistry”. Thanks to its biodegradability, low cost and renewability, starch is thereby considered as a promising candidate for the development of environmentally friendly materials with multifunctional properties. Although starch can be utilized as filler, thermoplastic starch (TPS) is preferred as obtained after melt-processing native starch in the presence of plasticizers such as water and glycerol. Thanks to its high ability to spontaneously self-assemble in function of temperature and water, starch-based materials could be considered as an interesting platform for shape-memory performances. Shape memory polymers (SMP) are stimulus-responsive materials able to change their shape by applying an external stimulus, such as temperature, humidity, pH, electric or magnetic field, etc. The shape-memory effect is not inherent and requires to carry out a two stage process called “programming” and “recovery”, respectively. In the first one, the “programming”, the material is deformed and fixed in a “temporary shape”. In the second stage, upon application of the external stimulus, the material recovers its initial permanent “fixed shape”. Hence, the aim of this work is to design smart multi-responsive (bio)materials and in particular to investigate both water- and thermally-activated shape-memory effects on blends based on TPS and ethylene-vinyl acetate (EVA). In these multi-shape memory systems, starch, water-responsive, is responsible for the shape memory behavior in response to relative humidity while EVA is temperature-responsive.