Abstract
Hydrophilic copolymers containing 2,2′:6′,2″-terpyridine moieties and acrylic acid (AA) units poly (acrylic acid-co-4-(2,2′:6′,2″-terpyridin-4′-yl)styrene) (P(AA-co-TPY)) were synthesized and characterized. Coordinated with different transition metal ions, the dilute aqueous solution of the copolymers exhibited red-shifted UV-vis absorption peaks of π-π* transition from 317 to 340 nm. Further, interacting with iron ions, the copolymer showed new absorption peaks at a longer wavelength region (570 nm) and the absorption intensity enhanced with increase of the ion concentration. When enough ions were added to coordinate with the 2,2′:6′,2″-terpyridine moieties, novel metallo-supramolecular hydrogels were obtained due to the formation of metal coordination bonds between polymer back bones and transition metal ions (Ni2+, Zn2+, Cd2+, Fe2+ and Cu2+), which acted as self-assembly crosslinking structures. The mechanical strength and morphology of the resulting metallo-supramolecular hydrogels have been investigated.
Highlights
While molecular chemistry is based on covalent bonds, supramolecular chemistry has been developed as the chemistry of the entities generated via intermolecular non-covalent interactions [1].Supramolecular polymers (SP) are those in which the monomers are held together by noncovalent interactions such as host-quest recognition, hydrogen bonds, electrostatic force, metal ion coordination, ð-ð interactions and so on, and can be used to bring monomeric building blocks together to form SP backbones [2,3,4,5,6].As polymers with lightly crosslinked network structures, hydrogels have been extensively studied since the 1950s [7]
The terpyridine-based monomer was prepared from the precursor 4-(2,20 :60,200 -terpyridin-40 -yl) recrystallizing in dichloromethane and methanol, pale yellow crystals (6.71 g, 84.5%) were methylbenzene with a good yield
Using the appropriate ratio of copolymer ligand and metal ions, novel metallo-supramolecular hydrogels were prepared that were self-assembly crosslinked by coordination bonds between the 2,20 :60,200 -terpyridine moieties and transition metal ions
Summary
While molecular chemistry is based on covalent bonds, supramolecular chemistry has been developed as the chemistry of the entities generated via intermolecular non-covalent interactions [1].Supramolecular polymers (SP) are those in which the monomers are held together by noncovalent interactions such as host-quest recognition, hydrogen bonds, electrostatic force, metal ion coordination, ð-ð interactions and so on, and can be used to bring monomeric building blocks together to form SP backbones [2,3,4,5,6].As polymers with lightly crosslinked network structures, hydrogels have been extensively studied since the 1950s [7]. Over the past few decades, enormous research interest has been directed towards the development of novel supramolecular hydrogels, in which the supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions occurs [19]. Due to their dynamic behavior, these novel polymeric networks usually exhibit attractive properties such as stimuli-responsiveness and self-healing for use in a wide variety of emerging applications [20]
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