Microgels prepared without exogenous crosslinker have recently been explored for diverse applications in biotechnology. However, our fundamental understanding of structure-property relationships for this class of materials is still lacking, especially in the context of more complex structures such as core-shell particles. In this article, core-shell microgels were prepared by seed-mediated, surfactant-free emulsion polymerization using a N,N ′-methylenebis (acrylamide) (BIS) cross-linked poly( N -isopropylacrylamide) (pNIPAm) microgel core upon which a crosslinker-free poly( N -isopropylacrylamide)-co-acrylic acid (ULC10AAc) shell was synthesized. Dynamic light scattering (DLS) and phase analysis light scattering (PALS) measurements show that the hydrodynamic radius and electrophoretic mobility of the core-shell microgels increase significantly with increasing pH due to the pH responsive ULC10AAc shell, while the temperature sensitivity of the microgels is also strongly pH dependent. The turbidity and the temperature-dependent scattering intensity plots of microgels at different pH also provide insight into the charged state of the microgels under the studied conditions. For example, we observe multiple temperature-induced transitions when the pH is either 4.5 or 6.5, illustrating that the core and shell domains, while remaining mechanically connected, are only partially coupled thermodynamically. These studies provide insight into the perturbation of ULC microgel behavior that might be brought about due to the presence of a higher density core region. Complex architectures such as these are relevant in biotechnology applications where the soft, deformable ULC shell is advantageous to control the polymer-biology interface, but a denser core region might be required to obtain a higher loading of encapsulated therapeutics, tracking dyes, or oligonucleotides. Thus, it is important to understand the synthetic conditions that allow a ULC shell to remain “ULC-like” despite the presence of a denser core. Graphical abstract

中文翻译：

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具有交联核的 pH 和温度敏感性超低交联微凝胶的消溶胀研究

最近已经探索了在不使用外源性交联剂的情况下制备的微凝胶在生物技术中的多种应用。然而，我们对这类材料的结构-性能关系的基本理解仍然缺乏，尤其是在核壳颗粒等更复杂结构的背景下。在本文中，使用 N,N'-亚甲基双（丙烯酰胺）（BIS）交联聚（N-异丙基丙烯酰胺）（pNIPAm）微凝胶核，通过种子介导的无表面活性剂乳液聚合制备核壳微凝胶合成了不含交联剂的聚（N-异丙基丙烯酰胺）-共聚丙烯酸（ULC10AAc）壳。动态光散射 (DLS) 和相分析光散射 (PALS) 测量表明，由于 ULC10AAc 壳具有 pH 响应性，核壳微凝胶的流体动力学半径和电泳迁移率随着 pH 值的增加而显着增加，而微凝胶的温度敏感性为也强烈依赖于 pH 值。微凝胶在不同 pH 下的浊度和温度依赖性散射强度图也提供了对研究条件下微凝胶带电状态的洞察。例如，当 pH 值为 4.5 或 6.5 时，我们观察到多个温度引起的转变，说明核域和壳域在保持机械连接的同时，仅在热力学上部分耦合。这些研究提供了对 ULC 微凝胶行为扰动的深入了解，这种扰动可能由于存在更高密度的核心区域而引起。诸如此类的复杂结构与生物技术应用相关，其中柔软、可变形的 ULC 壳有利于控制聚合物-生物界面，但可能需要更密集的核心区域才能获得更高负载的封装治疗剂、示踪染料或寡核苷酸。因此，了解使 ULC 壳保持“类似 ULC”的合成条件是很重要的，尽管存在更致密的核。图形概要 可变形的 ULC 壳有利于控制聚合物-生物界面，但可能需要更密集的核心区域才能获得更高负载的封装治疗剂、示踪染料或寡核苷酸。因此，了解使 ULC 壳保持“类似 ULC”的合成条件是很重要的，尽管存在更致密的核。图形概要 可变形的 ULC 壳有利于控制聚合物-生物界面，但可能需要更密集的核心区域才能获得更高负载的封装治疗剂、示踪染料或寡核苷酸。因此，了解使 ULC 壳保持“类似 ULC”的合成条件是很重要的，尽管存在更致密的核。图形概要