Structure and molecular conformation of tussah silk fibroin films: Effect of heat treatment

✍ Scribed by Giuliano Freddi; Patrizia Monti; Masanobu Nagura; Yohko Gotoh; Masuhiro Tsukada

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 188 KB
• Volume: 35
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19970415)35:5<841::aid-polb13>3.0.co;2-a

✦ Synopsis

Structural changes of tussah ( Antheraea pernyi ) silk fibroin films induced by heat treatment were studied as a function of the treatment temperature in the range 200-250ЊC. The DSC curve of tussah films with a-helix molecular conformation displayed characteristic endo and exo peaks at 216 and 226ЊC, respectively. These peaks first weakened and then completely disappeared after heating at 230ЊC. Accordingly, the TMA thermal shrinkage at 206ЊC disappeared when the films were heated at 230ЊC. The onset of weight loss was monitored at 210ЊC by means of TG measurements. X-ray diffraction profiles gradually changed from a-helix to b-sheet crystalline structure as the treatment temperature increased from 200 to 250ЊC. On raising the heating temperature above 200ЊC, the intensity of IR and Raman bands characteristic of b-sheet conformation increased in the whole ranges of amide and skeletal modes. The sample treated at 200ЊC showed a spectral pattern intermediate between a-helix and b-sheet molecular conformation. The IR marker band for random coil structure, still detectable at 200ЊC, disappeared at higher treatment temperatures. Spectral changes attributable to the onset of thermal degradation appeared at 230ЊC.