Random coil configuration of the polyformals (CH 2O (CH 2) yO-): 4. Dipole moments of poly(1,3-dioxocane) ( y =5) and poly(1,3-dioxonane) ( y = 6)

Abstract

Samples of poly(1,3-dioxocane) [CH 2O(CH 2) 5O-] and poly(1,3-dioxonane) [CH 2O(CH 2) 6O-] were prepared by reacting paraformaldehyde with 1,5-pentanediol and 1,6-hexanediol, respectively. Fractions of both polymers, obtained by liquid-liquid precipitation separations, were studied in benzene solutions by means of dielectric constant measurements from 20 to 60°C. Mean-square dipole moments 〈 μ 2〉 0 thus obtained were compared with theoretical results based on rotational isomeric state models of the two chains. Very good agreement is obtained for the magnitudes of the dipole moments, and for their dependence on chain length and temperature. Values of the dipole moment ratio 〈μ 2〉 0 nm 2 , where n is the number of bond dipoles of moment m, are essentially the same for the polyformals corresponding to y = 2,4,5, and 6. This indicates that even the very short CH 2CH 2 non-polar sequences strongly suppress the correlations between the polar oxymethylene CH 2OCH 2OCH 2 sequences in this type of chain. The configurational analysis also identifies the lowest energy conformations of poly(1,3-dioxocane) and poly(1,3-dioxonane), and they are found to be the conformations adopted by the chains in crystalline state.