Conformational analysis of higher poly(oxyalkylenes) using empirical force field calculations

Abstract

AbstractThe conformational energies for the various rotational isomers of model compounds for poly(oxytrimethylene), POM3, and poly(oxytetramethylene), POM4, were calculated by means of the empirical force field method, and statistical mechanics calculations were made for the configuration‐dependent properties of POM3 and POM4. Although the dipole moment ratios of these polymers directly calculated from the results of the force field calculations agreed well with the observed ones, the estimated characteristic ratios did not agree with the observed ones. When the two geometric parameters of POM3 were changed, excellent agreement between the experimental values and the estimated ones was obtained. In case of POM4, when only geometric parameters were changed, the agreement was less satisfactory. The value for the interaction energy Eσ, which is directly derived from the result of the force field calculation for the model compound of POM4, seems to be overestimated because of a fault minimum. The value for the interaction energy Eσ is estimated to be the same as for POM3. Moreover, when the four geometric parameters were changed, the estimated values agreed well with the experimental ones. The direct use of the results of the force field calculations is not always satisfactory, but the parameters obtained are a good initial set of parameters to reproduce the observed configuration‐dependent properties.