Abstract
Poly (ethylene glycol) (PEG) oligomer forms itself into a complex with barbiturates and with urea. The stability of the complexes was studied by kinetic analysis of TG curves for thermal decomposition in N2. Activation energies obtained by the OZAWA method are 106.8 and 84.7kJ mol-1 for the urea-PEG 4000 complex and urea, respectively. The time required for 10% weight decrease at the isothermal condition of 100°C was 7 hours for the urea-PEG complex while it was only 3 hours for pure urea. The activation energies of the barbiturate complexes found are nearly equal to those of corresponding pure barbiturates. The urea complex decomposes according to the first order mechanism but the decomposition of barbiturate complexes is expressed as the zero order reaction.
