| A kind of cellulose whiskers were extracted from the branch-barks of mulberry (Morus alba L.) by an alkali treatment at 130°C and subsequently a sulfuric acid hydrolysis. AFM image showed that the diameter of obtained whiskers was ranged from 20 nm to 40 nm. The chemical compositions analysis, FT-IR, XRD results indicated that the hemicellulose and lignin were removed extensively in the cellulose whiskers, with a crystallinity of 73.4%. The TGA curves implied a two-stage thermal decomposition behavior of cellulose whisker due to the introduction of sulfated groups into the crystals in the sulfuric acid hydrolysis process. The obtained whiskers may have the potential applications in the fields of composites as a reinforcing phase, as well as in pharmaceutical and optical industries as additives.The flexible and transparent composite films were fabricated by a mixture of silk fibroin, poly(ethylene glycol) and mulberry cellulose nanowhiskers. The cellulose nanowhiskers were uniformly dispersed in the matrix when its content was as high as 12 w/w%. The tensile properties of composite films generally depended on the nanowhisker content, but significantly improved when compared with the pure SF film. DMA analysis revealed that the alpha transition temperature increased gradually with the increase of nanowhisker content, probably due to the formation of interactions between the nanowhiskers and the silk fibroin molecular chains, leading to the mobility reduction of the amorphous silk fibroin. A preliminary biocompatibility study of the nanocomposite films was carried out and the results showed an increment of MG-63 cell numbers attached on the MCW filled films and the morphologies of cells on them looked more flatten and spread, which are attributed to the much more complex surfaces properties of the nanocomposites. This kind of flexible silk fibroin-matrix composite films may possess the potential utilizations in the extended biomedical application fields.
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