The possibility of a low-temperature glass transition is proposed for two poly(amino acid)s: poly(L-methionine) and poly(L-serine). The suggestion is based on deviations of the experimental heat capacity from values calculated from the vibrational spectrum. The discrepancy consists in an increase of the heat capacity over a wide temperature range (260-400 K) to values more typical of liquids. Qualitative experiments are performed that show the rubbery nature of the samples above room temperature and brittleness below. The broadness of the proposed glass transition may be caused by the presence of some low level of crystallinity. It is speculated that the motion begins in the side groups around room temperature and causes a gradual devitrification of the whole molecule at higher temperatures.
Посилання на статтю:
A possible glass transition for poly(L-methionine) and poly(L-serine) / A. Xenopoulos*, K. Roles and B. Wunderlich // Polymer. – 1993. – Vol 34. – P. 2559-2563.