Thermoresponsive polymers as macromolecular coordination ligands: complexation-dependence of thermally induced aggregation in aqueous solution

We have designed novel macromolecular coordination ligands (MCLs) by conjugation of thermoresponsive polymers based on poly(N-isopropylacrylamide) (M-n around 3 to 25 kg mol(-1)) with 1,2,4-triazole coordination sites. These triazole units were integrated into two fundamentally different MCL architectures via reversible addition-fragmentation chain transfer polymerization following two synthetic strategies: (I) The customized chain transfer agent 1-{[3-(4H-1,2,4-triazol-4-yl)propyl]amino}-2-methyl-1-oxopropan-2-yl dodecyl carbonotrithioate (DMP-APTRZ) was employed for hemi-telechelic MCLs with a single triazole end group. (II) A tailored comonomer N-[3-(4H-1,2,4-triazol-4-yl)propyl]methacrylamide (APTRZMAAm) provides access to multidentate MCLs with a controllable number of triazole side groups along the polymer backbone. The thermally controlled variation of the MCL volume demand in aqueous solution was exploited for reversible aggregate formation upon Fe2+ complexation. Thermal response was studied via UV/Vis turbidity measurements, aggregate dimensions were determined via DLS, while the aggregate morphology was analyzed via customized TEM.

Automated summary

Novel macromolecular coordination ligands (MCLs) were designed by conjugating thermoresponsive polymers with 1,2,4-triazole coordination sites, leading to reversible aggregate formation. The thermal response, aggregate dimensions, and morphology were studied for potential applications in coordination chemistry.