Separation performance of alcohol-induced silk fibroin membranes with homogeneous and heterogeneous microstructures

Biological membranes were prepared from silk fibroin (SF) to investigate the mechanism SF microstructure that induced by different alcohols (C1-C4OH). SF membranes which were induced by less carbon of alcohols had a more hydrophilic surface (similar to 44.4 degrees) than that induced by multi-carbon alcohol (similar to 80.5 degrees). Positron annihilation spectrum showed that treating SF membrane using highly polar methanol/water generates heterogeneous structures. The internal hydrophobic segment had more beta-sheets and smaller free volume than the internal hydrophilic segments because the latter flipped over to the surface. Consequently, the methanol/water-induced SF membrane showed excellent isopropyl alcohol separation efficiency. The low polar butanol/water-induced SF membranes formed homogeneous structures with a more hydrophobic surface and a larger total free volume than the methanol/water-induced SF membranes. Therefore, the crystallinity of the SF membranes could be controlled through different alcohols/water treatment, where the homogeneous phase could transform into the heterogeneous phase.

Automated summary

The microstructure and properties of silk fibroin membranes can be controlled by treatment with different alcohols/water. SF membranes treated with highly polar methanol/water exhibit better hydrophilicity and separation efficiency, while SF membranes treated with low polar butanol/water show increased hydrophobicity and larger free volume.