Silk-inspired polyurethane containing glyalaglyala tetrapeptide. III. morphological, thermal, and mechanical features of electrosprayed and electrospun deposition.

Morphological, thermal, and mechanical features of electrosprayed and electrospun deposition of the silk-inspired polyurethane (PU) containing GlycineAlanineGlycineAlanine (GlyAlaGlyAla, the featured peptide sequence of silkworm silk fibroin) tetrapeptide, which was synthesized by the traditional liquid-phase peptide synthesis method and the classical two-step polymerization method using Boc-protected amino acids and diisocyanates as starting materials, were characterized. The results show that the synthesized silk-inspired PU dissolved in tetrahydrofuran (THF) can be easily electrosprayed or electrospun into the film form, although its molecular weight ranging from 13,000 to 15,000 is quite low. Elastomeric fibrous membranes with surface morphologies of 'droplets,' 'bead-on-string,' and 'nonwoven fibers' have been obtained by electrospraying and electrospinning the silk-inspired PU/THF solution of varying concentrations. The thermograms confirm high thermostability of the silk-inspired PU between 350 and 400°C due to the polar peptide linkages. The tanδ peak of dynamic mechanical analysis curve corresponding to its glass transition temperatures is detected at −34.3°C. Its elongation at break is about 140-150%, and the breaking tensile strength ranges from 22 to 27 MPa, which is consistent with the data of other PUs containing l-alanine residue. Information provided by this study can be used to better understand the correlation between the natural and man-made silk polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40245. [ABSTRACT FROM AUTHOR]