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Open AccessArticle

Exploring the Structural Transformation Mechanism of Chinese and Thailand Silk Fibroin Fibers and Formic-Acid Fabricated Silk Films

by Qichun Liu 1,2, Fang Wang 1,*, Zhenggui Gu 2, Qingyu Ma 3 and Xiao Hu 4,5,6,*
1
Center of Analysis and Testing, Nanjing Normal University, Nanjing 210023, China
2
School of Chemistry and Materials Science, Nanjing Normal University Jiangsu, Nanjing 210023, China
3
School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
4
Department of Physics and Astronomy, Rowan University, Glassboro, NJ 08028, USA
5
Department of Biomedical Engineering, Rowan University, Glassboro, NJ 08028, USA
6
Department of Molecular and Cellular Biosciences, Rowan University, Glassboro, NJ 08028, USA
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2018, 19(11), 3309; https://doi.org/10.3390/ijms19113309
Received: 19 September 2018 / Revised: 13 October 2018 / Accepted: 22 October 2018 / Published: 24 October 2018
(This article belongs to the Special Issue Synthesis and Applications of Biopolymer Composites)
Silk fibroin (SF) is a protein polymer derived from insects, which has unique mechanical properties and tunable biodegradation rate due to its variable structures. Here, the variability of structural, thermal, and mechanical properties of two domesticated silk films (Chinese and Thailand B. Mori) regenerated from formic acid solution, as well as their original fibers, were compared and investigated using dynamic mechanical analysis (DMA) and Fourier transform infrared spectrometry (FTIR). Four relaxation events appeared clearly during the temperature region of 25 °C to 280 °C in DMA curves, and their disorder degree (fdis) and glass transition temperature (Tg) were predicted using Group Interaction Modeling (GIM). Compared with Thai (Thailand) regenerated silks, Chin (Chinese) silks possess a lower Tg, higher fdis, and better elasticity and mechanical strength. As the calcium chloride content in the initial processing solvent increases (1%–6%), the Tg of the final SF samples gradually decrease, while their fdis increase. Besides, SF with more non-crystalline structures shows high plasticity. Two α- relaxations in the glass transition region of tan δ curve were identified due to the structural transition of silk protein. These findings provide a new perspective for the design of advanced protein biomaterials with different secondary structures, and facilitate a comprehensive understanding of the structure-property relationship of various biopolymers in the future. View Full-Text
Keywords: silk fibroin; glass transition; DMA; FTIR; stress-strain silk fibroin; glass transition; DMA; FTIR; stress-strain
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MDPI and ACS Style

Liu, Q.; Wang, F.; Gu, Z.; Ma, Q.; Hu, X. Exploring the Structural Transformation Mechanism of Chinese and Thailand Silk Fibroin Fibers and Formic-Acid Fabricated Silk Films. Int. J. Mol. Sci. 2018, 19, 3309.

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