In the present work we used microgels as colloidal containers for the loading of hydrophobic magnetic nanoparticles using the solvent exchange method. We varied systematically two parameters: (i) the crosslinking degree of microgels (1–4.5 mol% crosslinker) and (ii) loading of hydrophobic magnetite nanoparticles (d = 7 nm) in microgels (2–10 wt%). The experimental data show that the interplay between these two parameters provides efficient control over the clustering of magnetic nanoparticles in the microgel structure. Transverse magnetization relaxation measurements indicate that the formation of nanoparticle clusters in microgels induces non-linear enhancement of the relaxivity with the increase of nanoparticle loading in microgels. The results suggest that the modulation of the microgel network architecture can be efficiently applied to trigger self-assembly processes inside microgels and design hybrid colloids with unusual morphologies and properties.

中文翻译：

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微凝胶中磁性纳米粒子的可调谐簇：通过调节网络体系结构提高磁弛豫性†

在目前的工作中，我们使用微凝胶作为胶体容器，通过溶剂交换方法装载疏水性磁性纳米颗粒。我们系统地改变了两个参数：（i）微凝胶的交联度（1-4.5 mol％交联剂）和（ii）疏水磁铁矿纳米颗粒的负载量（d= 7 nm）（2-10 wt％）。实验数据表明，这两个参数之间的相互作用提供了对微凝胶结构中磁性纳米粒子簇的有效控制。横向磁化弛豫测量结果表明，随着微凝胶中纳米颗粒负载的增加，微凝胶中纳米颗粒簇的形成会引起弛豫性的非线性增强。结果表明，微凝胶网络体系结构的调制可以有效地应用于触发微凝胶内部的自组装过程，并设计具有异常形态和特性的混合胶体。