Abstract: A full-relaxation optimization of molecular structure and the Dreiding Ⅱ force field are employed to obtain the geometry parameters and the conformational energies of meso and racemic dyad of poly(vinyl methyl ether)(PVME). It is found in this study that three different side-group orientations result in different energetic contour maps. A reasonable RIS model of PVME has thus been built up based on the statistical average of the energies from the three different orientation models. The characteristic ratio of PVME calculated was found to be agreement with the experiment result. Therefore, considering the orientation of side-group allows us to satisfactorily reproduce the experimental dimensions of random PVME chain.

Key words: Poly(vinyl methyl ether), Side-group orientation, Conformational energy, Characteristic ratio