The homogeneous grafting of both poly (ethylene glycol) allenyl methyl ether macromonomer (PEGA39), and 2-acrylamido-2-methylpropane sulphonic acid (AMPS) onto ethyl cellulose (EC) was carried out in benzene and benzene: ethanol (1 : 1 v/v ratio) solvent systems, respectively. The thermal decomposition behaviour of the grafted products, ethyl cellulose and homopolymers was investigated using TGA and DTG thermal methods. The thermal stability of the grafted products EC-g-PEGA39 are increased by increasing the macromonomer content, whereas the decomposition temperatures of the grafted products with AMPS (EC-g-AMPS) are decreased remarkably in most cases compared to those of ethyl cellulose and PAMPS. The activation energies of the decompositions are determined and related to the thermal stabilities of the various polymers. (C) 2000 Kluwer Academic Publishers.