A new thermoresponsive double hydrophilic block copolymer bearing a terpyridine moiety formed a hydrogel with a sol–gel thermoreversible transition in the presence of Fe 2+ ions.
A well-defined poly( N, N-dimethylacrylamide)- b-poly( N-isopropylacrylamide- co-2-vinyl-4,4-dimethylazlactone) thermoresponsive double hydrophilic block copolymer bearing a terpyridine entity (Tpy-PDMA- b-P(NIPAM- co-VDM)) was synthesized by successive RAFT polymerizations. An amphiphilic macro-chain transfer agent bearing a terpyridine moiety (Tpy-PDMA-CTA) was synthesized and used for the preparation of a double hydrophilic block copolymer (Tpy-PDMA- b-P(NIPAM- co-VDM)) by RAFT dispersion polymerization. The RAFT dispersion polymerization of water-soluble monomers showed good control over the molar mass and dispersity, as characterized by size exclusion chromatography (SEC) and 1H-NMR spectroscopy. Complexation in the presence of metal ions (Fe 2+) and self-assembly of the Tpy-PDMA- b-P(NIPAM- co-VDM) copolymer in diluted solution (0.5% w/v) were investigated. The formation of dynamic metallo-supramolecular flower-like micelles was demonstrated by UV-Vis spectrophotometry and dynamic light scattering (DLS). The effect of the addition of Fe 2+ ions to a concentrated solution (8% w/v) of the Tpy-PDMA- b-P(NIPAM- co-VDM) copolymer at low temperature was investigated and the thermal profile of the metallic bis-terpyridine complex ([Fe(Tpy-PDMA- b-P(NIPAM- co-VDM)) 2] 2+) has been studied by differential scanning calorimetry (DSC). The influence of temperature on the aqueous solution (8% w/v) of the ([Fe(Tpy-PDMA- b-P(NIPAM- co-VDM)) 2] 2+) metallic complex was investigated by rotational rheometry. The results show that the self-assembly of the thermoresponsive block of the metallic bis-terpyridine complex formed a dynamic hydrogel with a sol–gel thermoreversible transition.