Iron(III) ion reinforced P(NiPAAm‐ co ‐AA) beads as tunable smart organogels

Abstract

P(NiPAAm‐ co ‐AA) organogel beads were prepared by UV‐induced droplet polymerization and mechanically reinforced through treatment with iron(III) chloride. Energy‐dispersive X‐ray spectroscopy mapping revealed a structure generation dependent on the amount of iron incorporation: beads with a low iron(III) loading have a core–shell architecture; high loadings result in a more homogeneous distribution of the ions over the particle volume. Fourier transform infrared analysis and proton release indicate coordination of iron(III) ions to formed carboxylic entities in the copolymer. A colorimetric thiocyanate assay allowed us to quantify the iron uptake, identifying a limit at a ratio of Fe ³⁺ to COOH entities of approximately 1:3.8. The compressive Young's modulus of the 5 mm beads increased by a factor of 378 from 6.1 kPa in the parent gel to 2.3 MPa in the Fe ³⁺ ‐saturated beads. The gels show a highly reversible shrinkage and swelling during solvent exchange between ethanol and ethyl acetate. The reinforced beads with a low and a high Fe ³⁺ content conditioned in ethanol undergo a shrinkage of their volume after immersing in ethyl acetate of 38% and 25%, respectively; the time constants for shrinkage increase most significantly with the iron content; the rate of swelling is comparable. No iron(III) leaching was detected over multiple swelling–shrinkage cycles. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.