Complex formation of silk fibroin with poly(acrylic acid)

Silk fibroin (SF) and poly(acrylic acid) (PAA) can interact when their aqueous solutions were mixed. Viscometric study showed that SF/PAA complex formation depended on the ratios of SF and PAA in dilute solution. SF/PAA complexes varied from soluble state to gel and to precipitate when both concentrations of mixed solution were increased gradually. FT-IR results showed that PAA and SF were liable to form interpolymer hydrogen bonds, and SF conformation changed in the complexes. FT-IR spectra also suggested the formation and crystal perfection of PAA/SF complex crystal relied on the ratios of SF and PAA, which were confirmed by the observation of X-ray diffraction.