鈥淚nverse Polyampholyte鈥?Hydrogels from Double-Cationic Hydrogels: Synthesis by RAFT Polymerization and Characterization

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• 作者：Kyriaki S. Pafiti ; Marios Elladiou ; Costas S. Patrickios
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：March 11, 2014
• 年：2014
• 卷：47
• 期：5
• 页码：1819-1827
• 全文大小：454K
• 年卷期：v.47,no.5(March 11, 2014)
• ISSN：1520-5835

文摘

We present two novel, homologous, pyridine-based monomers, 2-(pyridin-2-yl)ethyl methacrylate (PyEMA) and (pyridin-2-yl)methyl methacrylate (PyMMA), which, despite their structural similarity, the former can be readily thermolyzed to methacrylic acid, while the latter remains intact under the same conditions. This was most dramatically demonstrated in the present work, where PyEMA and PyMMA were randomly terpolymerized with a dimethacrylate cross-linker using reversible addition鈥揻ragmentation chain transfer polymerization to yield weakly double-cationic polyelectrolyte hydrogels of three different compositions which, upon thermal treatment, they were readily converted to polyampholyte hydrogels. While the parent double-cationic polyelectrolyte hydrogels exhibited a swelling response only to low-pH conditions, the daughter polyampholyte hydrogels presented swelling responses to both high- and low-pH conditions. Owing to the relative values of the effective pK_a鈥檚 of the weakly acidic and weakly basic units, with the latter being lower than the former (鈥渋nverse polyampholyte鈥?behavior), the swelling profiles of the daughter hydrogels were insensitive to polyampholyte composition.