Improved united atom force field for poly(dimethylsiloxane)

We develop a new united atom force field for computer simulations of poly(dimethylsiloxane) (PDMS) malts. The model is based on an explicit atom, class II potential studied previously. The effects of partial charges on the intermolecular structure are found to be stronger in the united atom model than in the explicit atom model, due to the lack of explicit hydrogen atoms. By adjusting the partial charges of the united atom force field, we obtain reasonable agreement with the results of the explicit atom model for the intermolecular structure, the pressure, and the chain dimensions in the melt.