Layer-by-layer polyelectrolyte architectures with ultra-fast and high loading/release properties for copper ions

The solid surfaces functionalization with high number of organic moieties from polymer chains became an interesting route to obtain new materials which can load/release a wide variety of chemical compounds due to the stimuli responsiveness (pH, ionic strength, temperature, solvent quality) of the organic part. Weak polyelectrolytes are very useful materials in construction of composite systems with thin layer-by-layer organic films on the surface with high potential in solid phase extraction. Herein, two facile strategies to modify silica microparticle surfaces with single branched poly(ethyleneimine) (PEI) multilayers are reported, the formed composites having ultra-fast response and high capacity for multiple loading/release of copper ions from aqueous solutions. The composites were obtained using a layer-by-layer technique in which PEI and poly(acrylic acid) (PAA) (strategy A) or PEI4-Cu complex and PAA (strategy B) were alternately deposited and cross-linked with glutaraldehyde (GA) onto silica microparticles. Silica//(PEI)(n) composites were obtained after PAA extraction in basic media from silica//(PEI/PAA)(n) composites or after Cu2+ and PAA extraction from silica//(PEI4-Cu/PAA)(n) composites. The amount of loaded Cu2+ depended on the amount of composites organic part, while the kinetic of sorption depended more on the flexibility and accessibility of functional groups inside the (PEI)(n) film. The maximum recorded value, after 10 cycles of loading/release of copper ions onto silica//(PEI) 7, was (similar to)12 mg Cu2+/g composite (or (similar to)200 mg Cu2+/g polymer). Composite microparticles based on cross-linked PEI chains on the surface of silica could be very promising solid supports for using in multiple loading/release of heavy metal ions with applications in water purification or in chromatography.