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Characterization of polyurethane and a silk fibroin-polyurethane composite fiber studied with NMR spectroscopies

Polymer Journal volume 54, pages 803–813 (2022)Cite this article

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Abstract

Recently, Bombyx mori silk fibroin (SF) has played a crucial role in biomedical applications. However, due to the highly ordered β-sheet structure in SF, the flexibility of SF fiber is relatively poor, which limits its application in biomaterials. In this paper, a SF-polyurethane (PU) composite fiber was prepared to increase the flexibility of SF fiber. PU prepared by a reaction of mainly a copolymer of polyhexamethylene carbonate diol and polycaprolactone diol (PHC/PCL-diol) with 4,4’-diphenylmethane diisocyanate (MDI) was used. First, the 1H and 13C solution NMR peaks of PU were assigned to groups in detail. In addition, the 13C solid-state NMR spectrum of PU was analyzed. Then, regenerated SF-PU composite fiber was prepared by the wet spinning method. The elongation at break of the fiber increased by 1.3-1.8 times compared with that of regenerated SF fiber, although there was no significant increase in tensile strength. The main reason for the increased flexibility of the SF-PU composite fiber is the increase in the fraction of random coils in SF, which was clearly observed by 13C solid-state NMR.

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Acknowledgements

We acknowledge Mr. Y. Ibe and Mr. K. Jono (Tosoh Co.) for kindly providing polyurethanes that they had synthesized. T.A. also acknowledges support by a JSPS KAKENHI Grant-in-Aid for Scientific Research 599 (C), grant number JP19K05609.

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  1. Material Analysis Research Center, Teijin Ltd, 4-3-2, Asahigaoka, Hino, Tokyo, 191-8512, Japan

    Koto Suganuma

  2. Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo, 184-8588, Japan

    Hironori Matsuda & Tetsuo Asakura

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  1. Koto Suganuma
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KS: Data collection and analysis, writing-original draft. TA: Conceptualization and analysis, writing-original draft, review & editing. HM: Data collection and analysis, review & editing. All authors read and approved the final manuscript.

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Correspondence to Koto Suganuma.

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Suganuma, K., Matsuda, H. & Asakura, T. Characterization of polyurethane and a silk fibroin-polyurethane composite fiber studied with NMR spectroscopies. Polym J 54, 803–813 (2022). https://doi.org/10.1038/s41428-022-00629-9

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