Tough and strong biomimetic soy protein films with excellent UV-shielding performance

To develop strong and tough bio-based composite films as replacements for synthetic polymer films is challenging. Based on the strong adhesion of the comb-like structure of geckos’ feet or pressure-sensitive resins on substrates, a comb-like polymer-aminated dialdehyde starch (A-DAS) was designed and prepared from polyamide polyamine polymer and dialdehyde starch via a Schiff-based reaction, and then combined with soy protein isolate (SPI) to develop a protein-based film. The comb-like A-DAS exhibited strong adhesion with SPI molecules by forming multiple hydrogen bonds, which created a noncovalent network that improved both the strength and toughness of the resultant film. The results showed that after integrating A-DAS (SPI:A-DAS weight ratio of 2:1), the tensile strength of the film dramatically increased by 1072.2% to 25.09 MPa, which is markedly better than that of other reported protein-based films. The toughness of the SPI/A-DAS film increased to 16.74 MJ/m3. Notably, the modified film could block 100% of the ultraviolet transmittance (<400 nm) owing to the imine group in A-DAS. This strategy offers a simple and effective way to construct strong and tough composite materials with ultraviolet-barrier performance, indicating potential applications in tissue engineering, hydrogels, and coating modification.