Bioinspired colored degradable starch-based films with excellent tensile strength

Starch-based films (SBFs) have received extensively attention in many fields due to their outstanding performance in biodegradability, renewability, and enormous production. However, the poor dyeability and tensile strength of the SBFs limited their practical application. Herein, colored biodegradable SBFs reinforced with straw fibers (F-SBFs) was designed. Straw fibers extracted by high temperature alkali treatment was applied to strengthen the SBFs matrix. At the same time, the coloring process of F-SBFs was realized by assembling monodispersed silicon dioxide nanoparticles into periodic arrays on the surface of F-SBFs, which was bioinspired by the structural colors of the plants and animals in nature. Mechanical, thermal, and visual properties of modified SBFs were investigated, meanwhile FT-IR, XRD, SEM, DSC, and TG were utilized in characterization. F-SBFs achieved higher tensile strength (from 10.1 MPa to 42.8 MPa) and melting temperature (from 77.4 degrees C to 87.6 degrees C), yet the elongation at break reduced to a low level (from 28.1% to 3.5%). The SEM micrographs of F-SBFs showed that the excellent compatibility between starch and straw fibers as well as the cross-linking among fibers was responsible for the improvement of mechanical and thermal properties. F-SBFs were endowed with the iridescent and non-iridescent structural colors by introducing the artificial nanostructure (photonic crystal) into the SBFs system. Some colored patterns were printed on SBFs which could be used for the information presentation.

Automated summary

Colored biodegradable starch-based films reinforced with straw fibers were designed to improve the mechanical and thermal properties. The addition of silicon dioxide nanoparticles on the surface created iridescent and non-iridescent structural colors, enhancing the aesthetic appeal and functionality of the films.