A novel silk-based segmented block copolymer containing GlyAlaGlyAla ?-sheets templated by phenoxathiin

Abstract

A novel segmented block copolymer, containing polyethylene glycol segment and GlyAlaGlyAla sequence derived from B. mori silk, has been prepared as a model for silk-based materials using both solution and interfacial techniques. Inherent viscosity, size exclusion chromatography, and light-scattering measurements gave molecular weight between M w 34,000 -39,000. Evidence for phase separation was provided by differential scanning calorimetry, which gave two T g 's at 57 C and 111 C, and transmission electron microscopy, which showed a morphology in which the peptide domain, estimated to be about 20 -50 nm, was dispersed in the continuous polyether phase. Solid-state FTIR spectroscopic results showed that the polymer contained both parallel and antiparallel -sheet stacks, and that the solution-polymerized material has the higher -sheet content. This was further confirmed by 13 C NMR, which gave about 80% total -sheet content for the solution-polymerized product and about 40% for the polymer obtained by interfacial polymerization.