By high-precision dynamic calorimetry the temperature dependences of heat capacity of dimethylene urethane (DMU) between 320 and 370 K and partially crystalline poly(dimethylene urethane) (PDMU) in the range 326-490 K at standard pressure have been determined within +/-1.5%. The thermodynamic characteristics of fusion of the substances, namely the temperature interval of melting, temperature, enthalpy and entropy of fusion, as well as the characteristics of devitrification and glassy state for poly(dimethylene urethane) have been estimated. The first and the second cryoscopic constants have been calculated for dimethylene urethane. The experimental data obtained in the present work and literature findings on the heat capacity of the substances were used to calculate their thermodynamic functions: the heat capacity C(p)degrees (T), enthalpy Hdegrees(T) - Hdegrees(0), entropy Sdegrees(T) and Gibbs function Gdegrees(T) - Hdegrees(0) over the range from T --> 0 to (370-480) K. Based on the data, the thermodynamic characteristics of polymerization process with five-membered ring opening Delta(pol)Hdegrees, Delta(pol)Sdegrees and Delta(pol)Gdegrees of dimethylene urethane with the formation of linear partially crystalline poly(dimethylene urethane) have been evaluated. (C) 2003 Elsevier B.V. All rights reserved.