The emulsion-solvent evaporation method has been widely employed as a route to achieve three-dimensional confined assembly for preparing block copolymer (BCP) microparticles. The interfacial property of emulsion droplets plays an important role in controlling the shapes and internal structures of the microparticles. In this report, we employed iron oxide nanoparticles (NPs) covered by pH-responsive poly(acrylic acid)-b-polystyrene (Fe₃O₄@PAA-b-PS) to control the oil/water interfacial interaction and the morphology of the resulting polystyrene-b-poly(dimethylsiloxane) (PS-b-PDMS) microparticles. A dramatic deformation of BCP microparticles from ellipsoidal Janus pupa-like particles to spherical onion-like particles was achieved by varying the location of Fe₃O₄@PAA-b-PS NPs through adjusting the pH value of the aqueous phase. The mechanism for the deformation was systemically investigated by varying the pH value of the aqueous phase, the weight fraction of Fe₃O₄@PAA-b-PS NPs in the oil phase, and the property of aqueous surfactants. Moreover, these Fe₃O₄-loaded hybrid BCP microparticles showed morphology-dependent T₂-weighted magnetic resonance imaging (MRI) performance, which may provide an alternative route to optimize the efficiency of MRI contrast agents.

中文翻译：

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通过pH响应纳米粒子的可控定位可变形嵌段共聚物微粒。

乳液-溶剂蒸发法已被广泛用作实现制备嵌段共聚物（BCP）微粒的三维受限组装的途径。乳液液滴的界面性质在控制微粒的形状和内部结构中起着重要作用。在本报告中，我们采用了pH响应型聚丙烯酸（丙烯酸）-b-聚苯乙烯（Fe ₃ O ₄ @ PAA- b -PS）覆盖的氧化铁纳米颗粒（NPs ）来控制油/水界面相互作用和分子筛的形貌。生成的聚苯乙烯-b-聚二甲基硅氧烷（PS- b-PDMS）微粒。通过调节水相的pH值来改变Fe ₃ O ₄ @ PAA- b -PS NPs的位置，从而使BCP微粒从椭圆形的Janus pupa类颗粒转变为球形的洋葱状颗粒。通过改变水相的pH值，油相中Fe ₃ O ₄ @ PAA- b -PS NPs的重量分数以及水性表面活性剂的性质，系统地研究了变形的机理。此外，这些装载Fe ₃ O _4的杂化BCP微粒表现出形态依赖性的T _2。加权磁共振成像（MRI）性能，可以提供优化MRI造影剂效率的替代途径。