New polyether and poly(ether ketone)s containing the rigid 1,6-diazaspiro[4.4]nonane-2,7-dione (spirodilactam) core in the backbone are described. The polymers are soluble in common solvents from which clear, colorless films are readily cast. Excellent thermo-oxidative stability is shown by all of the systems studied with TGA stabilities up to 595 degrees C or 598 degrees C in air and argon respectively. Dielectric constants ranged from 2.53 to 3.00 and water absorption results were nil to 3.6%. (c) 2006 Elsevier Ltd. All rights reserved.