Synthesis and characterization of thermally-responsive polyurethane bionanocomposites

Resumen

The studies of this work concern the synthesis and characterization of segmented thermoplastic polyurethanes and their bionanocomposites with high contents of carbon from renewable resources. To his end, vegetable oil-based polyols, corn sugar-based chain extender, and chitin and cellulose nanocrystals were used as renewable nanofillers, because the use of components derived from renewable resources for the synthesis, makes these materials interesting from the viewpoint of environmental impact. Moreover, hard and soft phase crystallinities were changed varying soft and hard segment contents and their chemical composition and molecular weight, as well as including cellulose and chitin nanocrystals, observing an increase in the microphase separation, thermo-mechanical stability and stiffness with increasing hard and soft phase crystallinities and nanocrystal content.Despite the increasing efforts to explore polymers from renewable resources, in particular also polyurethanes, examples of shape-memory polymers based on renewable monomers are still rare. Thus, in this work, we study the thermally-activated shape-memory properties of the synthesized segmented polyurethanes and bionanocomposites. Cyclic thermo-mechanical tests performed at 60 °C showed that these materials are excellent candidates for use as thermally-activated shape-memory polymers, in which the crystalline soft phases promote high shape fixity (close to 100%) and the hard phase crystallites ensure outstanding shape recovery (80-100%, depending on the hard segment and nanocrystal content). Finally, the short-term cytotoxicity assays revealed that these materials are good candidates for use as stimulu responsive materials in biomedical applications.