화학공학소재연구정보센터
Macromolecules, Vol.31, No.25, 8907-8911, 1998
Correlation times of motion of deuterium oxide in polyamide 6 rods
Deuterium nuclear magnetic resonance (NMR) studies of varying amounts of D2O absorbed in undrawn commercial polyamide 6 (PA6) rods at room temperature suggest the presence of only one type of water closely associated with amide sites via hydrogen bonding and that its motion can be modeled as both isotropic rotational and translational diffusion. Time constants for spin-lattice relaxation (T-1) and spin-spin relaxation (T-2) are used to obtain correlation times for the motions. The dependence of T-1 on D2O content shows a minimum, indicating that the correlation time is on the order of omega(0)tau(c) similar to 1. Translational diffusion occurs on the time scale of less than 1 ms and describes the motion of D2O hopping between different solvated sites. The corresponding range of diffusivity of D2O in PA6, similar to 10(-10) cm(2)/s, agrees with values reported for macroscopic diffusion measurements. Within each solvated site the solvent molecules undergo isotropic reorientation diffusion on the order of nanoseconds. The correlation times of both motions increase with decreasing D2O content, a trend consistent with plasticization of the polyamide matrix. No evidence is found for "free" water. Solid echo experiments also show that there is slow exchange (similar to 10(-5) s) between deuterium oxide and the ND bonds of PA6.