Experimental values at different temperatures of the mean-square dipole moment, (mu(2)),of 2,2’-bisphthalimido diethyl ether (PTDE) and 1,8-bisphthalimido-3,6-dioxaoctane (PTDO), model compounds of imide-ether molecular chains, are reported. The values obtained for this quantity in dioxane are 8.28-8.31 D-2 and 11.04-11.22 D-2 for PTDE and PTDO, respectively, in the temperature range 20-50 degrees C. These results indicate that imide-ether chains exhibit much lower polarity than their benzamide-ether counterparts. The interpretation of the H-1 NMR spectrum of PTDE suggests that an increase in the polarity of the solvent raises the gauche population about NCH2-CH2O bonds. Both the NMR results and the conformational energy calculations by semiempirical methods suggest that these bonds are nearly freely rotating. However, the evaluation of the mean-square dipole moments as a function of the energy of gauche states about NCH2-CH2O bonds indicates that good agreement between theory and experiments is obtained for values of this energy 0.4 +/- 0.2 K cal mol(-1) above that of the alternative trans states.