A Supramolecular Hydrogel Based on Copolymers of Acrylic Acid and Maleic Anhydride Derivatives with Terpyridine Motifs

Abstract

A kind of terpyridine derivative (NH2-Tpy) in which the amino was incorporated by a short alkyl chain was synthesized. Through grafting of terpyridine units into the hydrophilic copolymers of maleic anhydride and acrylic acid PAAMa via the reaction of the amino groups in NH2-Tpy and the maleic anhydride units, a series of gelator polymers—P1, P2, and P3—containing different contents of terpyridine units was synthesized. Under coordination of Ni2+ and terpyridine ligands in linear polymers, the supramolecular hydrogels H1, H2, and H3 with different cross-linking degrees were prepared. The linear polymers P1–P3 had a strong absorption peak at about 290 nm in the UV-vis spectra which was attributed to π–π* transition, and there was a new peak at about 335 nm led by the metal-to-ligands charge transfer (MLCT) when coordinated with Ni2+ ions. According to the rheological behaviors, the storage modulus (G′) was larger than the loss modulus (G′′). These hydrogels showed typical gel-like characteristics when the terpyridine content of the hydrogels exceeded 10%, and the hydrogels showed liquid-like characteristics when the terpyridine content of the hydrogels was less than 7%. The results of the micromorphological investigation of the xerogels from SEM illustrated the metal–terpyridine coordination cross-linking could have an important influence on the microstructures of the resulting hydrogels. Furthermore, these hydrogels based on supramolecular cross-links exhibited reversible solution–gel transition at different environmental temperatures. At the same time, the equilibrium swelling of the supramolecular hydrogels was 8.0–12.3 g/g, which increased with the decrease in the content of the terpyridine units in the resulting hydrogels.

Special Issue: Synthesis, Processing, Structure and Properties of Polymer Materials

“…In this Special Issue, 33 original articles have been published on various topics, including the preparation, characterization, and some examples of application of polymeric materials. This issue includes review articles [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] and research articles [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

“…The scope of research articles of papers included a Special Issue is very wide. It includes papers on the synthesis and study of the properties of new thermoplastic polymers [ 9 , 10 , 11 , 12 , 13 ], obtaining of composites [ 14 , 15 , 16 ], nanocomposites [ 17 , 18 , 19 ], microspheres [ 20 , 21 ], polymeric blends [ 22 , 23 , 24 ], hydrophobic nanostructures [ 25 ], polymeric membranes [ 26 , 27 ], hydrogels [ 28 ] and others [ 29 , 30 , 31 , 32 , 33 ].…”

“…Chi et al [ 28 ] obtained and characterized novel metal-supramolecular hydrogels. The hydrophilic polymers were based on acrylic acid and maleic anhydride, and in addition, the polymer chain was grafted with terpyridine units.…”

Effect of Coordination Sacrificial Bond Strength on Toughening Properties of Polyesters

“…The difficulty lies in the design of a system where other effects are similar while only the SB strength is different. This is hard to be achieved in most systems but is feasible when using metal-coordination interactions as SBs since the strength of coordination bonds can be flexibly tuned by varying the metal ions. − However, the interactions of pyridine-type ligands with transition metals are usually very weak; thus, their effects on the properties of elastomers are hard to be investigated. Compared to mono- and bidentate ligands, tridentate ligands exhibit a much larger binding affinity range due to the efficient chelation.…”