Solid state side chain transitions of poly(alpha-amino acids). I. Investigation by differential scanning calorimetry

The differential scanning calorimetric behavior of a series of alpha-amino acid homopolymers and copolymers was investigated in the range of temperature from -80 to +130 degrees C. The following polymers have been examined: poly(N'-carbobenzoxy-L-lysine), poly(O-carbobenzoxy-L-tyrosine), random copolymers of O-carbobenzoxy-L-tyrosine and N'-carbobenzoxy-L-lysine, poly(Ngamma-carbobenzoxy-L-diaminobutyric acid), and poly(N sigma-carbobenzoxy-L-ornithine). Each sample exhibited a prominent glass-like transition between +30 and +60 degrees C with a specific heat increment deltacp of the order of 0.03-0.11 cal/(g degrees C). Endothermal peaks, developed by annealing, have been also been revealed. It is concluded that in poly(alpha-amino acids) side chain motions are capable of undergoing glass-like transition.