Advanced thermal analysis methods were used to characterize a new family of recombinant spider silk-like block copolymers based on the amino acid sequences of the dragline silk of Nephila clavipes [1]. The block copolymer, named BA, is comprised of well defined amino acid sequences: an alanine-rich hydrophobic block, A, and a glycine-rich hydrophilic block, B. A model [2] based on the vibrational, rotational and translational motions of the constituent poly(amino acid)s was used to predict the specific reversing heat capacity, C_p(T), which is crucial to the design of smart biomaterials. Excellent agreement was found between the theoretical value and the measured C_p(T) determined by temperature modulated differential scanning calorimetry (TMDSC) in combination with thermogravimetric analysis (TGA). Using temperature modulated differential scanning calorimetry with a thermal cycling method and thermogravimetry, we also captured the effect of bound water acting as a plasticizer for recombinant spider silk-like block copolymer films which had been cast from water solution and dried. A low glass transition due to bound water removal was observed in the first heating cycle, after which, a shift of glass transition can be observed in A-block film due to crystallization and annealing, and in BA film due to annealing. No shift of glass transition after bound water removal was observed in B-block film. Support was provided from the National Science Foundation, Division of Chemical, Bioengineering, Environmental, and Transport Systems, through CBET-0828028 and the MRI Program under DMR-0520655 for thermal analysis instrumentation.
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