Multiple Hydrogen Bonding Enables Strong, Tough, and Recyclable Soy Protein Films

Despite the recent advances in the recycling of petroleum-based materials, there is an urgent need to expand the range of applications of the biobased recyclable polymers. Here, recyclable hyperbranched polyester (HBPE) toughened and enhanced soy protein (SP) films were prepared with a high mechanical strength and an excellent toughness. The HBPE-doped biomass films exhibited high tensile strength of 13.7 MPa, exceptional toughness of 11.8 MJ m(-3), and strain at break of up to 91.8%. The excellent mechanical properties were attributed to the increase in free volume fraction by the introduction of nanoscale cavities into the SP film matrix and the strong intermolecular sacrificial hydrogen bonds within the matrix. There, recyclable SP films have great potential to replace the petrochemical resources with renewable materials in polymer applications.