C-13 NMR spin-lattice relaxation times as a probe of local polymer dynamics in plasticized polyethers

C-13 NMR spin-lattice relaxation times T-1 are used to investigate the effect of low molecular,weight diluents, including N,N-dimethylformamide, N-methylformamide, propylene carbonate, gamma-butyrolactone, triglyme and tetraglyme, on the local polymer segmental motion in polyether-urethane;networks. In all cases, an increase in the local mobility is deduced from the increasing T,measurements consistent with a decreasing glass transition temperature. The-extent of plasticization; however, is dependent on the nature of the small molecules. Those molecules' which can either form strong polymer-diluent interaction's (for example through dipolar interactions) or are themselves rigid, give the least enhancement of polymer mobility and the greatest deviation from the Fox equation for T-g. In the presence of alkali metal salts, N,N-dimethylformamide and propylene carbonate are shown to have opposite effects on the local polymer motion, as seen from the T-1 measurements. In both cases, addition of the plasticizers increases the C-13 T-1 relaxation times for the plasticizer. However, propylene carbonate decreases the polymer C-13 T-1 whilst N,N-dimethylformamide results in the expected increase in polymer C-13 T-1.