DEPENDENCE OF THE SPECIFIC-HEAT IN GLASSY POLYBUTADIENE ON THERMAL HISTORY

The specific heat of glass-forming polybutadiene in the glass transiti on region depends strongly on the thermal history of the sample. After cooling and waiting at a temperature T(w) < T(g) (T(g) almost-equal-t o 178 K is the glass transition temperature) for a (constant) time t(w ), the peak value of the specific-heat anomaly at T(g) passes over a m aximum as a function of T(w) at T(w) almost-equal-to 169 K. The energy taken up by the sample when heating through T(g) after waiting at T(w ) = 169 K increases with t(w) and can be described by a Kohlrausch law DELTAQ(t(w)) approximately {1 - exp[-(t(w)/tau)beta]} with beta almos t-equal-to 0.5 and tau = = 100 min. Comparison with recent neutron-sca ttering data indicates that the different time scales of microscopic a nd macroscopic relaxations may be attributed to their different length scales.