Structure and Miscibility of Tussah Silk Fibroin/Carboxymethyl Chitosan Blend Films

摘要

Tussah silk fibroin (TSF)/carboxymethyl chitosan (CMCS) blend films were prepared by solution casting using water as a co-solvent. The conformational change of TSF and the miscibility of the two components in blend films were investigated by using FTIR spectroscopy, X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. Blending with CMCS induces a conformational change in TSF from α-helix to p-sheet and the most complete transformation to [3-sheet conformation occurs in blending with 5% CMCS. A mechanism is suggested for the conformational transition in which CMCS molecules are used as the nuclei of TSF micelles and induce TSF molecules to self-assemble by forming intermolecular hydrogen bonds. When CMCS content exceeds 5% in the blend film, the content of p-sheet conformation is reduced. The blend film, with 15% CMCS and above, exhibits semi-miscible characteristics, because there is a possibility of a two-phase structure formation in the blend film. However, the intermolecular interactions between the two polymers occur in their amorphous regions as indicated by FTIR analysis. The water solubility assays show that adding 3-7% CMCS results in significant improvement in water resistance of the TSF films, especially in the blend film with 5% CMCS, which hardly dissolves in water. However, when CMCS content exceeds 7% the water solubility of the blend films increases rapidly.