ABSTRACT:Configuration-dependent properties of the poly(oxyethylene) (POE) chain were calculated within the framework of the rotational isomeric state (RIS) approximation. Conformational energies of the chain have been determined by the 1 H and 13 C NMR studies on 1,2-dimethoxyethane (DME) and POE as described in our recent paper as well as in the present work. The unperturbed chain dimension C ( = Ix were calculated as a function of RIS parameters such as bond angles, rotational angles, and conformational energies. The value of C ( = 5.2) determined in organic solutions by Beech and Booth was found to be favorably reproduced by these calculations. The SANS result (C=6.9) recently reported by Kugler et al. on the melt exceeds the limit of a probable range estimated from uncertainties involved in each of the RIS parameters. Within the limit mentioned above, a set of RIS parameters was chosen so as to give an optimum agreement with observed values of the configurational properties of POE. Conformational energies thus estimated are as follows: E.= -0.5-kcal mol-1 for the C-C bond and EP =0.8 kcal mol-1 for the C-0 bond, both representing the energy of the gauche form expressed relative to the trans state. Use of the conformational energies (E.= -1.2 and EP = 1.1 kcal mol-1 ) determined in D 2 0 leads to a value of C= 3.2, suggesting that the end-to-end dimension of the chain for the state unperturbed by longrange interactions may be considerably small in pure water.