Structure and properties of tussah silk fibers graft-copolymerized with methacrylamide and 2-hydroxyethyl methacrylate

✍ Scribed by Masuhiro Tsukada; Giuliano Freddi; Maria Rosaria Massafra; Silvia Beretta

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 363 KB
• Volume: 67
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19980222)67:8<1393::aid-app5>3.0.co;2-9

✦ Synopsis

Tussah silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gain values were obtained with both grafting agents (up to 175%). The extent of homopolymerization was negligible for the MAA grafting system over the entire range of monomer-silk ratios examined, while polymer deposition on the fiber surface occurred when the HEMA-silk ratio exceeded 0.5% (w/w). The moisture content of poly(MAA)-grafted silk fibers was enhanced by grafting. Breaking load, elongation at break, and energy decreased at low weight gain (0-20%) and then remained rather constant. The DSC curves of poly(MAA)-grafted silk showed a new endotherm at about 280ЊC, due to the melting of poly(MAA) chains. The loss modulus peak of poly(HEMA)-grafted silk fibers broadened and shifted to a lower temperature, showing a tendency to split into two peaks at high weight gain. On the other hand, grafting with poly(MAA) induced a noticeable upward shift of the loss peak. The TMA curves showed that grafting with poly(MAA) resulted in a higher extent of fiber contraction from room temperature to about 250ЊC. Moreover, the intensity of the final contraction step at about 350ЊC decreased with increasing weight gain and shifted to a lower temperature. The Raman spectra of grafted fibers were characterized by overlapping of the characteristic lines of both silk fibroin and polymer, the latter showing an intensity proportional to the amount of weight gain. Among the conformationally sensitive vibrational modes of tussah silk fibroin, the amide III range was significantly modified by grafting with both poly(MAA) and poly(HEMA).