High-resolution solid-state C-13-NMR has been used to study the phase separation and molecular motion in two series of polyurethane foams. These two series differ by one possessing the additive of lithium chloride, LiCl. NMR relaxation times can map the motion throughout the polymer molecule and detect changes in that motion arising from either microseparation or phase mixing between the different segments. There are only slight changes in the soft segment T1rho(C-13) values as well as an increase in the hard segment T1rho(H-1) values with increase in the hard segment content for the foams studied. The T1rho(H-1) and T1rho(C-13) values do indicate that the phase separation of the hard and soft segments is similar for all foams. A decrease in the T1rho(H-1) and T1rho(C-13) values with increasing LiCl content indicates that the motion of the soft segments is restricted more by the hard segments. This is explained by more phase mixing in the foams containing the LiCl additive. (c) 1994 John Wiley & Sons, Inc.