Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Golm, Germany.
Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany.
J Phys Chem B. 2021 Apr 8;125(13):3398-3408. doi: 10.1021/acs.jpcb.0c10601. Epub 2021 Mar 26.
Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker ,,','-tetramethyl-,'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(-3-sulfopropyl-,-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers.
采用新型高水溶性交联剂,,','-四甲基-,'-双(2-乙基甲基丙烯酰基)-丙基-1,3-二铵二溴化物和磺基甜菜碱单体 2-(-3-磺丙基-,-二甲基铵基)乙基甲基丙烯酸酯，制备了具有分级结构的水凝胶。两种化合物的自由基聚合反应迅速，得到的水凝胶尺寸可达 5 厘米，近乎透明。流变学表明，单体与交联剂的比例与水凝胶的储能模量和损耗模量之间存在明显的相关性。冷冻扫描电子显微镜、低场核磁共振（NMR）光谱和小角 X 射线散射表明，凝胶具有纳米到亚毫米尺度的分级结构。NMR 研究受到凝胶的明显不均匀性和磺基甜菜碱单体复杂化学结构的挑战。NMR 光谱表明，通过考虑基于甲基丙烯酸酯单体侧链的流动性梯度的新型拟合方法，可以解决这些复杂性问题。
