title: Polyelectrolyte layer-by-layer deposition in cylindrical nanopores.
abstract: Layer-by-layer (LbL) deposition of polyelectrolytes within nanopores in terms of the pore size and the ionic strength was experimentally studied. Anodic aluminum oxide (AAO) membranes, which have aligned, cylindrical, nonintersecting pores, were used as a model nanoporous system. Furthermore, the AAO membranes were also employed as planar optical waveguides to enable in situ monitoring of the LbL process within the nanopores by optical waveguide spectroscopy (OWS). Structurally well-defined N,N-disubstituted hydrazine phosphorus-containing dendrimers of the fourth generation, with peripherally charged groups and diameters of approximately 7 nm, were used as the model polyelectrolytes. The pore diameter of the AAO was varied between 30-116 nm and the ionic strength was varied over 3 orders of magnitude. The dependence of the deposited layer thickness on ionic strength within the nanopores is found to be significantly stronger than LbL deposition on a planar surface. Furthermore, deposition within the nanopores can become inhibited even if the pore diameter is much larger than the diameter of the G4-polyelectrolyte, or if the screening length is insignificant relative to the dendrimer diameter at high ionic strengths. Our results will aid in the template preparation of polyelectrolyte multilayer nanotubes, and our experimental approach may be useful for investigating theories regarding the partitioning of nano-objects within nanopores where electrostatic interactions are dominant. Furthermore, we show that the enhanced ionic strength dependence of polyelectrolyte transport within the nanopores can be used to selectively deposit a LbL multilayer atop a nanoporous substrate.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, D55128, Mainz, Germany.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Lazzara
authors.forename: K H Aaron
authors.initials: KH
authors.lastname: Lau
authors.forename: Ahmed I
authors.initials: AI
authors.lastname: Abou-Kandil
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Caminade
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Majoral
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Knoll
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D008567:Membranes, Artificial; D058608:Nanopores; D036103:Nanotechnology / Q000379:methods*; D009994:Osmolar Concentration; D013057:Spectrum Analysis
chemical_list: D050091:Dendrimers; D004573:Electrolytes; D008567:Membranes, Artificial; D000537:Aluminum Oxide