Design and preparation of thermo-responsive vinylamine-containing micro-gel particles for reversible absorption of carbon dioxide

To obtain a temperature-responsive CO₂ absorbent with a high amine content, temperature-responsive gel particles (GPs) consisting of poly(N-isopropylacrylamide-co-polyvinylamine) (poly(NIPAm-co-VAm)) were designed and prepared. Stable poly(N-isopropylacrylamide) GPs with a high N-vinylformamide (NVF) content were prepared in aqueous media by optimization of the concentrations of the surfactant and monomers used in the polymerization step. GPs with a high polyvinylamine (pVAm) content up to 3.2 mmol amine per g GPs (∼30 mol%) were prepared as a stable aqueous solution via the complete and selective hydrolysis of pNVF in the poly(NIPAm-co-NVF) GPs in a methanol solution, then dialyzed against water. The GPs with 3.2 mmol amine per g GPs pVAm showed a volume phase transition at a temperature of ∼65 °C. Conductivity experiments established that the aqueous solution of the poly(NIPAm-co-VAm) GPs reversibly absorbed CO₂ in response to a small thermal stimulus (30-75 °C). In addition, the foaming of amine-functionalized GP solutions during CO₂ bubbling was prevented by increasing the amount of crosslinking in the GPs.