Novel thermo and ion-responsive copolymers based on metallo-base pair directed host-guest complexation for highly selective recognition of Hg 2+ in aqueous solution.

The development of materials with highly selective recognition towards Hg ²⁺ is of great significance in environmental monitoring. Herein, a novel thermo-responsive copolymer with Hg ²⁺ recognition property is prepared via thermally-initiated copolymerization of 5'-O-Acryloyl 5-methyl-uridine (APU) and N-isopropylacrylamide (NIPAM). The chemical structure and stimuli-sensitive properties of poly(N-isopropylacrylamide-co-5-methyl-uridine) (P(NIPAM-co-APU)) linear polymers and hydrogel are thoroughly investigated. At the supramolecular level, P(NIPAM-co-APU) linear polymers could respond to both temperature and Hg ²⁺ stimuli with highly selective recognition towards Hg ²⁺ over other 18 metal ion species (at least 5 fold difference) and common anions. Upon capturing Hg ²⁺ by APU units as host metal receptors, the lower critical solution temperature (LCST) of P(NIPAM-co-APU, PNU-7 and PNU-11) linear polymers are significantly shifted more than 10 °C due to the formation of stable APU-Hg ²⁺ -APU directed host-guest complexes. Accordingly, at the macroscopic level, P(NIPAM-co-APU) hydrogel display selective and robust recognition of Hg ²⁺ under optimum conditions, and its maximum Hg ²⁺ uptake capacity was 33.1 mg g ^-1 . This work provides a new option for Hg ²⁺ recognition with high selectivity, which could be facilely integrated with other smart systems to achieve satisfactory detection of environmental Hg ²⁺ .
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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