Heat capacities of solid poly(amino acids). I. Polyglycine,poly(L-alanine), and poly(L-valine)

Heat capacities of polyglycine, poly(L -alanine), and poly(L -valine) were analyzed using approximate group vibrations and fitting of the skeletal vibrations to a two-parameter (Θ₁, Θ₃) Tarasov function. New experimental data were measured by differential scanning calorimetry in the temperature range of 230–390 K. Good agreement between our experimental data and the calculated data was observed for all three poly(amino acids). Previous investigations showed agreement between calculation and reported experimental data for only limited low temperature ranges. At higher temperatures, discrepancies of up to 55% existed between experiment and calculation. The cause of this discrepancy must be assumed to be experimental error. Recommended experimental data are revised on the basis of this investigation. Computed heat capacities are available for the three biopolymers in the solid state from 0 to 1000 K.