51822-75-4Relevant articles and documents
Multicomponent Diffusion of Distearyldimethylammonium Polyelectrolyte Solutions in the Presence of Salt: Coupled Transport of Sodium Chloride
Thies, Michael,Clancy, Shaun F.,Paradies, Henrich H.
, p. 9881 - 9891 (1996)
A sensitive conductance method has been used to determine binary and ternary diffusion coefficients of distearyldimethylammonium chloride, bromide, and hydroxide (DSDMACl, DSDMABr, and DSDMAOH) in aqueous solutions in the absence and presence of salt.Experiments were conducted above and below the critical micelle concentration (CMC) at 25 deg C, and the concentration of salt, when present, was 0.015 M NaX (X = Cl, OH, Br).The experiments reveal that diffusion of DSDMA chloride, bromide, and especially hydroxide induces concurrent flow of NaCl, NaBr, and NaOH, respectively.Also diffusion of DSDMAX in the presence of NaCl drives countertransport of DSDMACl or DSDMAOH.At pH 7.5 and an ionic strength of 0.015 M, each mole of diffusing DSDMACl (Nagg = 72, α = 0.15), cotransports 9.0 mol of NaCl.However, coupled flow of NaCl decreases as the solution pH approaches 5.2 and is almost zero at pH 4.5.The corresponding value for diffusing DSDMAOH at pH 7.5 is about 120 mol of NaCl.At pH 6.5 only 10 mol of NaCl are cotransported, and the value is almost zero at pH 5.5.However, at pH 4.5, diffusing DSDMAOH generates a counterflow of NaCl due to bound protons and a release of H2O (DSDMAOH + H(1+) DSDMA(1+) + H2O), yielding a net positive charge; hence, the D21 value is negative.The cross-diffusion coefficient D21 of diffusing DSDMACl in the presence of 0.015 M (0.095-0.009) NaOH and 0.015 M NaCl yields a flux density of NaOH and NaCl, which is generated by the DSDMAX (X = Cl + OH) gradient.A similar cross-diffusion coefficient, D21, is revealed when DSDMAOH, is used, instead of DSDMACl, in the presence of 0.015 M NaCl through induced coupled transport of salt.The coupled transport of NaCl or of NaCl and NaOH is primarily driven by the diffusion-induced electric field along the DSDMAOH and DSDMACl concentration gradients.For the DSDMAOH system, the direction and magnitude of the coupled flow of either NaCl or NaOH can be explained through the ionic mobility of DSDMA(1+) and OH(1-), in addition to the charge and degree of dissociation (Nagg = 6400, α = 0.33-0.35) at 25 deg C.The tracer and mutual diffusion coefficients for the DSDMAX system were compared with those from light-scattering measurements of polyelectrolyte solutions of DSDMAX.
