The Structure of Colloidal Polyethylenimine–silica Nanocomposite Microparticles

Deposition of silica from an organosilane tetraethoxysilane (TEOS) onto parent polyethylenimine (PEI) microgel particles produces a novel PEI–silica nanocomposite, which possesses greater adsorption capacity for copper ions than either parent material. This study explores factors governing interactions of silica with the PEI matrix, along with structural features of resulting PEI–silica composite particles, to explain their properties and determine their application potential. The influence of initial TEOS/PEI mass ratio and the duration of silica deposition on the final silica content and distribution in the composite are studied. A comparative analysis of the structural architecture of chemically etched silica remnants, original PEI–silica composite particles and the parent PEI-microgel is carried out using X-ray photoelectron spectroscopy, small-angle X-ray scattering, and electron microscopy techniques. It is found that silica sol nanoparticles are evenly distributed throughout the PEI-microgel framework and interlinked with it via electrostatic interactions, enabling a structural model of the PEI–silica nanocomposite to be proposed. The chemical stability of resulting nanocomposite particles in parallel with the parent PEI-microgel is tested and shown to be robust for more than 100 days of storage in aqueous dispersions across a range of pH conditions, highlighting the application potential for these particles in copper capture.