Poly(vinyl alcohol)-Based Hydrogels Formed by “Click Chemistry”

Abstract

Novel poly(vinyl alcohols) (PVA) functionalized with pendant acetylene and azide groups were prepared by carbonyldiimidazole (CDI)-mediated couplings of the amines terminated with functional groups, 1-azido-2-aminoethane, propargylamine, or N-methylpropargylamine, to PVA. Low degrees (1-5%) of PVA modification were required in order to retain solubility in water. Azide-modified PVA and alkyne-modified PVA components were cross-linked by mixing of their solutions together with Cu(I) catalyst, a type of Huisgen's 1,3-dipolar azide-alkyne cycloaddition, recently defined as a powerful "click" chemistry. Reaction of the two different polymers results in a chemoselective coupling between alkynyl and azido functional groups with the multiple formation of triazole cross-links to give hydrogel formation. In another version the PVA-based hydrogels were obtained by cross-linking of alkyne-modified PVA with the telechelic bifunctional poly(ethylene glycol)diazide cross-linker. The hydrogels prepared by these two methods were characterized by their equilibrium swelling in water, by their viscoelastic properties in the swollen state, and by their soluble fraction. It was demonstrated that network properties are affected by the type of cross-linker with polyfunctional PVA cross-linkers having higher gelation capacity than the bifunctional PEG cross-linker. The approach we describe here presents a promising alternative to a common chemical hydrogel preparation technique, which utilizes bifunctional low-molecularweight cross-linkers.

Click Chemistry, A Powerful Tool for Pharmaceutical Sciences

“…A few attempts have been made to use click chemistry to synthesize polymer networks with high efficiency and reduced defects (73)(74)(75). The problem with this approach, however, is the difficulty of removing copper catalyst from the network.…”

Thermoresponsive hydrogels in biomedical applications

“…More specifically, in situ forming hydrogels can provide a means for simple, "custom-made" therapeutics and diagnostics. A polymer solution can be prepared and allowed to gel in situ, after photopolymerization [4,5], chemical crosslinking [6,7], ionic crosslinking [8] or in response to an environmental stimulus such as temperature, pH or ionic strength of the surrounding medium [9,10]. Hydrogels that respond to temperature change are the subject of this review.…”

Regular Linking of Cellulose Nanocrystals via Click Chemistry: Synthesis and Formation of Cellulose Nanoplatelet Gels

“…26 They modified hyaluronic acid with the alkyne and azido groups to achieve suitable precursor for the 1,3-dipolar cycloaddition reaction. 9,15,16,[27][28][29] Once these precursors were mixed in the aqueous media substantial gel formation was observed. Recently, similar methodology has been successfully applied for cellulose modifications in heterogeneous media.…”