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Synthesis, Structural Characterization, and Thermoresponsivity of Hybrid Supramolecular Dendrimers Bearing a Polyoxometalate Core
Author(s) -
Chen Hailong,
Yang Yang,
Wang Yizhan,
Wu Lixin
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201300289
Subject(s) - dendrimer , polyoxometalate , lower critical solution temperature , supramolecular chemistry , chemistry , triethylene glycol , polymer chemistry , cationic polymerization , aqueous solution , solvent , chemical engineering , materials science , molecule , organic chemistry , polymer , engineering , copolymer , catalysis
A series of cationic dendrons bearing triethylene glycol monomethyl ether terminal groups of different generations have been synthesized and used to encapsulate an inorganic polyanionic cluster [K 12.5 Na 1.5 (NaP 5 W 30 O 110 )] through electrostatic interactions. The resulting dendritic cation–encapsulated polyoxometalate (POM) complexes, cluster–dendrimers, are soluble in water and exhibit lower critical solution temperatures (LCST). The thermoresponsivities of these complexes in aqueous solutions were studied by turbidimetry and variable‐temperature 1 H NMR spectroscopy. The observed cloud points show a remarkable dependence on the generation of the dendrons. Complexes composed of first‐generation dendrons exhibit no obvious thermoresponsive properties, but for complexes bearing second‐generation dendrons, the LCST decreases as the number of dendritic cations around the POM cluster increases. Complexes composed of third‐generation cations underwent reversible aggregation and disaggregation upon heating and cooling, respectively. This thermally induced self‐aggregation was characterized by DLS and TEM. In addition, the effects of salt and solvent on the LCST were investigated. This research demonstrates a new type of thermoresponsive dendritic organic–inorganic hybrid complex and provides a general route to the endowment of POMs with temperature‐sensitive properties through electrostatic interactions.