Heat capacities of cis-1,4-polyisoprene from 2 to 360 K

Heat capacities of amorphous synthetic cis-1,4-polyisoprene have been determined for the quenched and annealed glasses from 2 to T _g (around 200 K) and for the liquid from T _g to 360 K, with a precision of better than 0.05 percent above 15 K. T _g as determined from H versus T plots, is 203 K for the quenched glass and 198 K for the annealed glass. For the glasses the heat capacity values from this research are about 1 percent higher than that reported in 1935 for natural rubber hydrocarbon. For the liquid the result from this research agrees better (within 1 percent) with recently (1967) proposed values than those from the earlier experiment cited. Effects of crystallization and melting, stark rubber crystals, and additives (antioxidants and stabilizers) were also studied.