Effect of Poly(l-serine) Additives with Different Primary Structures on the Mechanical Properties of Poly(vinyl alcohol) Films.

Structural proteins consist of characteristic peptide motifs, such as β-sheets in silkworm and spider silks, and exhibit remarkable mechanical properties that depend on their amino acid sequences. In this study, two types of poly(l-serine) (polySer) with different primary structures, telechelic polySer and linear polySer, were synthesized by chemoenzymatic polymerization to utilize the ability of β-sheet structures to enhance the mechanical properties of polymeric materials. The β-sheet-forming polySers were incorporated into poly(vinyl alcohol) (PVA) films to improve their mechanical properties. It was revealed that both types of polySer formed β-sheet structures but exhibited different self-assembling features. Both types of polySer increased the Young's modulus of the PVA films, while the ductility and the toughness altered depending on the primary structures, due to the differences in their miscibility with PVA. These findings suggest a novel approach for enhancing the mechanical properties of polymer materials by designing the primary structure of peptides.