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Keratin sponge/hydrogel: I. Fabrication and characterization

Cardamone, Jeanette M, Tunick, Michael H, Onwulata, Charles
amino acids, denaturation, differential scanning calorimetry, dyeing, dyes, enthalpy, glass transition, hydrocolloids, hydrolysis, keratin, microstructure, modulus of elasticity, oxidation, rheology, temperature, thermal degradation, wool
Keratin sponge/hydrogels formed by oxidation and reduction hydrolysis of US domestic fine- or coarse-grade wool exhibited distinctively different topologies, each with unique porous structure. These materials retained amino acids and microstructure as protein homologues of intact keratin. Amphoteric character was confirmed by differential dyeing with anionic and cationic dyes. Differential scanning calorimetry (DSC) provided evidence of molecular organization and the behavior of occluded moisture through measurements of glass transition, peak temperature, thermal degradation temperature, enthalpy of water removal, and degradation (Tg, Tw, ΔHw, Tₜ, and ΔHₜ). The absence of denaturation peaks indicated highly crosslinked molecular association. Low ΔHw indicated high plasticity and the ability to absorb and retain moisture. Small amplitude strain analysis rheology to measure storage or elastic modulus, G′, and shear loss or viscous modulus, G′′, as a function of applied strain characterized the sponge/hydrogels as covalently crosslinked networks. With viscoelastic properties typical of both liquids and solids, they maintained their structural integrity under strain.