title: Layer-by-layer assembly of thick, Cu(2+)-chelating films.
abstract: Layer-by-layer adsorption of protonated poly(allylamine) (PAH) and deprotonated poly(N,N-dicarboxymethylallylamine) (PDCMAA) yields thick films with a high density of iminodiacetic acid (IDA) ligands that bind metal ions. When film deposition occurs at pH 3.0, PAH/PDCMAA bilayer thicknesses reach 200 nm, and Cu(2+) binding capacities are ~2.5 mmol per cm(3) of film. (PAH/PDCMAA)10 films deposited at pH 3.0 are 4-8-fold thicker than films formed at pH 5.0, 7.0, or 9.0, presumably because of the low charge density on PDCMAA chains at pH 3.0. However, with normalization to film thickness, all films bind similar amounts of Cu(2+) from pH 4.1 solutions of CuSO4. In micrometer-thick films, equilibration of binding sites with Cu(2+) requires ~4 h due to a low Cu(2+) diffusion coefficient (~2.6 × 10(-12) cm(2)/s). Sorption isotherms determined at several temperatures show that Cu(2+) binding is endothermic with a positive entropy (binding constants increase with increasing temperature), presumably because metal-ion complexation involves displacement of both a proton from IDA and water molecules from Cu(2+). (PAH/PDCMAA)10 films retain their binding capacity over four absorption/elution cycles and may prove useful in metal-ion scavenging, catalysis, and protein binding.
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: Salinda
authors.initials: S
authors.lastname: Wijeratne
authors.forename: Merlin L
authors.initials: ML
authors.lastname: Bruening
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Baker
mesh_terms: D000327:Adsorption; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004058:Diffusion; D006046:Gold / Q000737:chemistry; D007098:Imino Acids / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010316:Particle Size; D011073:Polyamines / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature
chemical_list: D002614:Chelating Agents; D007098:Imino Acids; D009942:Organometallic Compounds; D011073:Polyamines; C063994:polyallylamine; D006046:Gold; D003300:Copper; C008109:iminodiacetic acid
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