Synthesis of coumarin-containing multi-responsive CNC-grafted and free copolymers with application in nitrate ion removal from aqueous solutions.

Cellulose nanocrystals (CNC)-grafted and free copolymers were synthesized in three different ratios of DMAEMA and coumarin monomers (30:5, 40:7, and 50:10) through reversible addition-fragmentation chain transfer polymerization. These multi-responsive polymers to carbon dioxide (CO2), temperature, and light triggers can be used in nitrate ions removal from aqueous solutions. These amphiphilic copolymers were self-assembled to vesicular structures in water. Adsorption of nitrate ions was carried out by protonation of the CO2-responsive block with inserting of CO2. Proton nuclear magnetic resonance and thermogravimetric analysis were used to confirm the synthesis process. Responsivity to temperature, CO2, and light in addition to the adsorption of nitrate ions from aqueous solutions was studied by UV-vis spectroscopy and dynamic light scattering. By increasing the PDMAEMA content, the adsorption capacity has also increased. The CNC-grafted copolymers showed lower adsorption in comparison with the free copolymers. The CNC-grafted copolymers can be regenerated by light and filtration processes.