Ivanova, O. ; Soltwedel, O. ; Gopinadhan, M. ; Köhler, R. ; Steitz, R. ; Helm, C.A.: Immobile light water and proton - deuterium exchange in polyelectrolyte multilayers. Macromolecules 41 (2008), p. 7179-7185
10.1021/ma800456z
Abstract:
To describe the swelling of polyelectrolyte multilayers (PEMs) on a molecular scale, the PEM architecture is varied. The polyanion is poly(styrenesulfonate) (PSS) and the polycation poly(allylamine hydrochloride) (PAH). PEM either consists of 10 protonated polyelectrolyte bilayers (p10), 10 deuterated bilayers (d10), or two different blocks, p5d5 or d5p5. Prior to the exposure to 100% relative humidity (RH) D2O or H2O, the PEM is immersed in liquid D2O or H2O, respectively. The obtained scattering length density profiles provide insight into the exchange rates of the constituent molecules: The data indicate that three mobile protons of each PAH monomer are replaced by deuterium ions, yet most of the H2O molecules found in PEM at 0% RH remain bound at 100% RH D2O. This is in consistency with the fact that the core of PEM is in a glassy state. At 0% RH, the amount of bound water in the deuterated layers does not depend on the film architecture, whereas in the protonated layers it does.