ISSN:
0887-6266
Keywords:
tussah silk
;
fibroin
;
methanol treatment
;
α-helix structure
;
β-sheet structure
;
dynamic mechanical analysis
;
thermomechanical analysis
;
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The thermal response of tussah (Antheraea pernyi) silk fibroin films treated with different water-methanol solutions at 20°C was studied by means of dynamic mechanical (DMA) and thermomechanical (TMA) analyses as a function of methanol concentration and treatment time. The DMA curves of α-helix films (treated with ≥80% v/v methanol for 2 min and 100% methanol for 30 min) showed the sharp fall of storage modulus at about 190°C, and the loss peak in the range 207-213°C. The TMA curves were characterized by a thermal shrinkage at 209-211°C, immediately followed by an abrupt extension leading to film failure. Both storage and loss modulus curves significantly shifted upwards for β-sheet films, obtained by treatment with ≤60% methanol for 30 min. The loss peak exhibited a maximum at 236°C. Accordingly, the TMA shrinkage at above 200°C disappeared. The films broke beyond 330°C, failure being preceded by a broad contraction step. Intermediate DMA and TMA patterns were observed for the other solvent-treated films. The loss peak shifted to higher temperature (219-220°C), and a minor loss modulus component appeared at about 230°C. This coincided with the onset of a plateau region in the storage modulus curve. The TMA extension-contraction events in the range 200-300°C weakened, and the samples displayed a final broad contraction (peak temperature 326-338°C) before breaking. The DMA and TMA response of these films was attributed to partial annealing by solvent treatment, which resulted in the formation of nuclei of β-sheet crystallization within the film matrix. The increased thermal stability was probably due to the small β-sheet crystals formed, which acted as high-strength junctions between adjacent random coil and α-helix domains. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2717-2724, 1998
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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