Lithium and sodium salts of methacrylic acid were prepared and polymerised by free radical initiation. Monomers and polymers were characterised using infrared (FTIR) analyses and the glass transition temperatures of the polymers were determined by differential scanning calorimetry (DSC). The thermal degradation behaviour was studied using thermogravimetry (TG) and showed high thermal stability of the salts. The solid degradation products have been investigated by FTIR and the results suggest that methacrylic salts polymerise under heating prior to degradation. The spectra of the residues obtained from the degradation of the monomers and polymers showed that they are composed of metal carbonate/bicarbonate. (C) 2000 Elsevier Science Ltd. All nights reserved.