PHYSICAL-PROPERTIES AND STRUCTURE OF SILK .5. THERMAL-BEHAVIOR OF SILK FIBROIN IN RANDOM-COIL CONFORMATION

In the reported experiments, the thermal behavior of films of amorphous silk fibroin in the random-coil confirmation has been investigated in the temperature range 25-220 degree C by differential scanning calorimetry (DSC), thermal expansion, dynamic mechanical measurements, x-ray diffraction, and infrared spectroscopy. As the temperature is raised, water is lost up to about 100 degree C. Intramolecular and intermolecular hydrogen bonds are broken between 150 and 180 degree C. The glass transition is observed at 173 degree C by DSC. The random-coil yields beta -form transition accompanied by reformation of hydrogen bonds takes place above 180 degree C. Thermally induced crystallization to the beta -form crystals starts at about 190 degree C.