Roughness and Salt Annealing in a Polyelectrolyte Multilayer

Abstract

The surface roughness of polyelectrolyte multilayers made from poly(diallyldimethylammonium chloride), PDADMAC, and poly(styrene sulfonate), PSS, was measured as a function of film deposition conditions. For dry multilayers, the significant roughness which builds up for thicker films is much more apparent for multilayers terminated with PSS. Corresponding roughness for PDADMA-capped multilayers may be seen by imaging in situ under electrolyte. Roughness may be substantially reduced, but not eliminated, by annealing in salt. Annealing does not lead to loss of polyelectrolyte from the film, even under conditions where the salt concentration is high enough to place the film properties beyond the glass transition. Roughness does not correlate with the molecular weight of the polyelectrolyte and is thus not caused by solution or film polymer chain conformations. The wavelength of the roughness features is approximately proportional to film thickness, which supports a mechanism whereby roughness is generated by anisotropic swelling due to water and polyelectrolyte addition in a manner similar to water uptake in hydrogels. Roughness is preserved by the glassy PSS layer and probably incorporated within the film as it grows.

Label‐Free Bioanalysis Based on Low‐Q Whispering Gallery Modes: Rapid Preparation of Microsensors by Means of Layer‐by‐Layer Technology

“…The LbL process allows subsequent deposition of homogeneous polyelectrolyte layers of a few nanometers of thickness each. As reported in the literature, deposition of polyelectrolyte layers should have a negligible effect upon the surface roughness . In fact, this is confirmed by our WGM spectra of LbL‐coated PS beads in case of small number of deposited layers (<3 double layers).…”

Ultrafast Fabrication of Gradient Nanoporous All‐Polysaccharide Films as Strong, Superfast, and Multiresponsive Actuators

“…On the contrary of the ion‐out self‐shaping mechanism for temperature, the double folding deformation is triggered by diffusion of counter ions into the CS/SA film (referred to as ion‐in mechanism), which leads to the electrostatic screen of both complex and noncomplex segments of the polyelectrolytes (denoted as S C and S N‐C , respectively). The screening of S N‐C can lead to the de‐swelling of S N‐C and thus the de‐swelling of the film, whereas the screening of S C can destroy the electrostatic complexation of S C and result in the swelling of the complex film . From the swelling ratio variation curves with time (Figure S7b, Supporting Information), it can be seen that the complex film first de‐swells and then swells, indicating the deformations at early and late stage are driven by the electrostatic screen of S N‐C and S C segments, respectively.…”

Sacrificial polyelectrolyte multilayer coatings as an approach to membrane fouling control: Disassembly and regeneration mechanisms

“…(PAH/PMAA) 4 , or increased rejection, e.g. (PDADMAC/PMAA) 4 , the acid and base likely induce conformational changes in the film without removing sufficient PE to enhance permeability [52].…”