title: Shape-memory bionanocomposites based on chitin nanocrystals and thermoplastic polyurethane with a highly crystalline soft segment.
abstract: Shape-memory bionanocomposites based on a naturally sourced segmented thermoplastic polyurethane and chitin nanocrystals were synthesized, and their mechanical properties and thermally activated shape-memory behavior were studied. The chitin nanocrystals were incorporated during the synthesis of the prepolymer made from a castor oil-based difunctional polyol and hexamethylene diisocyanate. The polymerization was completed by addition of propanediol, as a corn-sugar based chain extender, bringing the weight content of components from renewable resources to >60%. Thermal analysis of the bionanocomposites revealed a phase-separated morphology, which is composed of soft and hard domains, which bestow the material with two melting transitions at 60 and 125 °C, that are exploitable for a shape memory effect. The soft segment is responsible for temporary shape fixing, while the hard segment crystallites are responsible for the permanent shape. The introduction of small amounts (0.25-2 wt %) of chitin nanocrystals was found to increase the crystallinity of the hard segment by way of nucleation, which in turn improves the shape recovery considerably. The thermally activated shape-memory behavior of the synthesized bionancomposites is exploitable with a programming and release temperature of 60 °C. The materials display good in vitro cell response, as shown by short-term cytotoxicity assays, and therefore, the bionanocomposites appear to be potentially useful for biomedical applications.
authors.affiliation: 'Materials + Technologies' Group, Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country UPV/EHU , Plaza de Europa 1, 20018, Donostia-San Sebastián, Spain.
authors.forename: Ainara
authors.initials: A
authors.lastname: Saralegi
authors.forename: Susana C M
authors.initials: SC
authors.lastname: Fernandes
authors.forename: Ana
authors.initials: A
authors.lastname: Alonso-Varona
authors.forename: Teodoro
authors.initials: T
authors.lastname: Palomares
authors.forename: E Johan
authors.initials: EJ
authors.lastname: Foster
authors.forename: Christoph
authors.initials: C
authors.lastname: Weder
authors.forename: Arantxa
authors.initials: A
authors.lastname: Eceiza
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Corcuera
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000633:toxicity; D002152:Calorimetry, Differential Scanning; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry*; D055119:Elastic Modulus; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D008422:Materials Testing; D051379:Mice; D018625:Microscopy, Atomic Force; D053761:Nanocomposites / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D011140:Polyurethanes / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: D001672:Biocompatible Materials; D011140:Polyurethanes; D002686:Chitin