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Linearly assembled polyelectrolyte multilayers (PEMs) are prepared by sequential adsorption of polyanions and polycations from 0.1 mol/L NaCl. The internal structure of PEMs is investigated with neutron reflectivity. The films are made from poly(ethylenimine) (PEI), poly(diallyldimethylammonium) (PDADMA) and poly(styrenesulfonate) (PSS or deuterated PSS-d). Each film consists of a protonated and a deuterated block, built from m protonated and n deuterated polycation/polyanion layer pairs, respectively. Annealing in salt solution (1 mol/L NaCl) allows the polyelectrolytes to gain entropy by adopting a more coiled conformation and by intermixing. During annealing the internal interface between the two blocks broadens due to interdiffusion; thus, the PSS diffusion coefficient is measured. Eventually the annealing leads to a uniform distribution of protonated and deuterated PSS throughout the film. Yet, if one polycation layer in the film center is branched PEI, then this PEI layer serves as a diffusion barri...

The internal interfaces of polyelectrolyte multilayers are investigated with neutron reflectivity. The films are made from poly(diallyldimethylammonium) (PDADMA), poly(styrenesulfonate) (PSS), and deuterated PSS-d. Each film consists of a protonated and a deuterated block. The internal roughness is smallest next to the film/air interface and increases with the number of layer pairs away from the film/air interface until a metastable state is reached. Both the final internal roughness and the interdiffusion constant increase with the salt concentration in the deposition solution and with PDADMA polymer weight. The increased mobility found with high molecular weight PDADMA is attributed to residual stresses occurring during film formation. The experiments suggest that PSS and PDADMA move partly as a complex. Postpreparation immersion in 1 M NaCl salt solutions has little effect if the multilayer is prepared from low salt solution and with high molecular weight PDADMA. However, almost complete intermixing is...

Using neutron reflectivity, the internal structure of polyelectrolyte multilayers is described on the nanoscale. Each film consists of a protonated and a deuterated block, built from x protonated and y deuterated polycation/polyanion bilayers, respectively. The number of bilayers N = x + y is kept constant; the position of the interface between the blocks is varied systematically. The polyanion is poly(styrenesulfonate) (PSS), and the polycation is poly(allylamine hydrochloride) (PAH) or poly(diallyldimethylammonium chloride) (PDADMAC). Always, the first four to five bilayers are thinner than the average bilayer thickness, but the three terminating bilayers are sometimes thicker. In the core zone, the bilayer thickness is constant. The internal roughness is smallest next to the film/air interface and increases with the number of bilayers away from the film/air interface. This suggests that each deposition step promotes the interdiffusion of the supporting layers. At the selected preparation conditions, th...

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...