A bio-hybrid material with special water affinity made from polyvinyl alcohol, rice starch and silk fibroin

A hybrid material composing of polyvinyl alcohol (PVA), rice starch (RS) and silk fibroin (SF) with opposite water affinity on each surface was successfully prepared. The hybrid material was prepared by placing PVA/RS/SF hydrogel onto glycerol-modified PVA/RS/SF film and leaving them to adhere. SF content in the hydrogels was optimized first by mixing various SF amounts to a mixture of PVA:RS (2:1 by weight). The 8.00 part per hundred of polymer (php) of SF was an appropriate concentration revealed by the maximum values of gel fraction and percent porosity. This SF content caused the blend to exhibit the highest water saturation and best mechanical properties. The glycerol-modified hydrophobic film with the same PVA/RS/SF composition was prepared and found that the water contact angle of the film had increased approximately three times after water soaking. The hybrid material was then prepared and characterized. As evidenced by physical appearance and SEM images, the interface between layers became homogeneous after 30 h layering time. Water contact angle values pointed out the hydrophilic nature of the hydrogel surface, while the film surface was hydrophobic. Coupling of the hydrogel with the film improved overall mechanical properties as indicated by stress and % elongation at break.