New thermally stable condensation polymers containing central ketal moieties derived from malonaldehydetetramethyl acetal and dihydroxyaromatic compounds
A number of new condensation polymers with acetal units in the main chain and having linear and ladder-form structure and high thermal stability were synthesized by solution polycondensation of dihydroxyaromatic compounds with malonaldehydetetramethyl acetal as a reactive protected 1,3-dicarbonyl compound. Optimal conditions for polycondensation were obtained via study of the model compounds. In order to obtain high molecular weight polymers, general investigations on the influence of reaction conditions, such as monomer concentration and reaction temperature were carried out. All polymers were obtained in high yields and moderate inherent viscosity ranging from 0.25 to 0.41 dL/g. The proposed chemical structures of condensation polymers were confirmed by 1H-NMR, 13C-NMR, FTIR spectroscopies, TGA, and DSC. Thermal analysis indicated that these polymers are stable up to 360 °C, and a 10% weight loss (T10) were recorded on the TG curves in the temperature range of 381–411 °C in nitrogen atmosphere, indicating their good thermal stability.