title: Heat Capacity of Spider Silk-like Block Copolymers.
abstract: We synthesized and characterized a new family of di-block copolymers based on the amino acid sequences ofNephila clavipesmajor ampulate dragline spider silk, having the form HABnand HBAn(n=1-3), comprising an alanine-rich hydrophobic block, A, a glycine-rich hydrophilic block, B, and a histidine tag, H. The reversing heat capacities, Cp(T), for temperatures below and above the glass transition, Tg, were measured by temperature modulated differential scanning calorimetry. For the solid state, we then calculated the heat capacities of our novel block copolymers based on the vibrational motions of the constituent poly(amino acid)s, whose heat capacities are known or can be estimated from the ATHAS Data Bank. For the liquid state, the heat capacity was estimated by using the rotational and translational motions in the polymer chain. Excellent agreement was found between the measured and calculated values of the heat capacity, showing that this method can serve as a standard by which to assess the Cpfor other biologically inspired block copolymers. The fraction of beta sheet crystallinity of spider silk block copolymers was also determined by using the predicted Cp, and was verified by wide angle X-ray diffraction and Fourier transform infrared spectroscopy. The glass transition temperatures of spider silk block copolymer were fitted by Kwei's equation and the results indicate that attractive interaction exists between the A-block and B-block.
authors.affiliation: Department of Physics and Astronomy, Tufts University, Medford, MA 02155, USA.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Huang
authors.forename: Sreevidhya
authors.initials: S
authors.lastname: Krishnaji
authors.forename: Xiao
authors.initials: X
authors.lastname: Hu
authors.forename: David
authors.initials: D
authors.lastname: Kaplan
authors.forename: Peggy
authors.initials: P
authors.lastname: Cebe
keywords: Block copolymer; Glass transition; Heat capacity; Infrared spectroscopy; Spider silk; Temperature modulated differential scanning calorimetry; X-ray diffraction