SUMMARY:In an adiabatic vacuum calorimeter the temperature dependence of the heat capacity C p 0 of tetramethylene urethane (TMU) (2-oxo-hexahydro-1,3-oxazepine) and poly(tetramethylene urethane) (PTMU) was studied between 4.3 and 300 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield the energies of combustion D U comb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions