title: Chain conformation and dynamics in spin-assisted weak polyelectrolyte multilayers.
abstract: We report on the effect of the deposition technique on film layering, stability, and chain mobility in weak polyelectrolyte layer-by-layer (LbL) films. Ellipsometry and neutron reflectometry (NR) showed that shear forces arising during spin-assisted assembly lead to smaller amounts of adsorbed polyelectrolytes within LbL films, result in a higher degree of internal film order, and dramatically improve stability of assemblies in salt solutions as compared to dip-assisted LbL assemblies. The underlying flattening of polyelectrolyte chains in spin-assisted LbL films was also revealed as an increase in ionization degree of the assembled weak polyelectrolytes. As demonstrated by fluorescence recovery after photobleaching (FRAP), strong binding between spin-deposited polyelectrolytes results in a significant slowdown of chain diffusion in salt solutions as compared to dip-deposited films. Moreover, salt-induced chain intermixing in the direction perpendicular to the substrate is largely inhibited in spin-deposited films, resulting in only subdiffusional (<2 Å) chain displacements even after 200 h exposure to 1 M NaCl solutions. This persistence of polyelectrolyte layering has important ramifications for multistage drug delivery and optical applications of LbL assemblies.
authors.affiliation: †Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Aliaksandr
authors.initials: A
authors.lastname: Zhuk
authors.affiliation: †Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Victor
authors.initials: V
authors.lastname: Selin
authors.affiliation: †Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Iryna
authors.initials: I
authors.lastname: Zhuk
authors.affiliation: ‡Columbia High School, Maplewood, New Jersey 07040, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Belov
authors.affiliation: §Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: Ankner
authors.affiliation: †Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States.
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Sukhishvili