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Issue 29, 2017
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Cross-linking of COOH-containing polymers using Ag(I)-catalyzed oxidative decarboxylation in aqueous solution

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Abstract

Cross-linking that defines the three-dimensional networks in hydrogels has a significant impact on their physiochemical properties. The cross-linking of hydrophilic polymers via post-polymerization reactions is an ideal way to manufacture hydrogels with high reproducibility and without monomer residuals. We herein report the use of Ag(I)-catalyzed oxidative decarboxylation to cross-link poly(acrylic acid) (PAA) and a family of COOH-containing hydrophilic polymers. Our method is based on the radical-mediated elimination reaction to remove COOH group(s) and generate alkyl radical(s) simultaneously, in the presence of AgNO3 and persulfates. The further intermolecular radical coupling is demonstrated to be very effective in inducing cross-linking and gelation of COOH-containing hydrophilic polymers. The cross-linking reaction can be readily achieved by simply mixing a small amount of AgNO3 (as low as 0.03 wt%) and persulfates with polymers at room temperature in air. Rheological measurements show that the gelation occurs in 20–30 min. The applications of oxidative decarboxylation in the preparation of hydrogels of COOH-containing hydrophilic copolymers and their interpenetrating polymer network (IPN) hydrogels are further validated. Finally, the residual Ag(I) ions in hydrogels are discussed in terms of how Ag(I) ions further change the mechanical and optical properties of hydrogels by photoreduction of Ag(I) to Ag nanoparticles. We expect that this Ag(I)-catalyzed oxidative decarboxylation chemistry can not only serve as a facile and general strategy to produce hydrogels through post-polymerization, but also enrich the toolbox of cross-linking chemistries of COOH-containing polymers in all forms (e.g. films, colloids and dispersions).

Graphical abstract: Cross-linking of COOH-containing polymers using Ag(i)-catalyzed oxidative decarboxylation in aqueous solution

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Publication details

The article was received on 27 Apr 2017, accepted on 13 Jun 2017 and first published on 13 Jun 2017


Article type: Paper
DOI: 10.1039/C7SM00825B
Citation: Soft Matter, 2017,13, 5028-5037
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    Cross-linking of COOH-containing polymers using Ag(I)-catalyzed oxidative decarboxylation in aqueous solution

    G. Weng, Y. Huang, S. Thanneeru, H. Li, A. Alamri and J. He, Soft Matter, 2017, 13, 5028
    DOI: 10.1039/C7SM00825B

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