Shang Meng, Ni Xinjiong, Xu Jiasheng, Cao Yuhua
School of Chemical and Material Engineering, Jiangnan University Wuxi 214122 People's Republic of China
RSC Adv. 2019 Dec 13;9(70):41280-41286. doi: 10.1039/c9ra08962d. eCollection 2019 Dec 9.
Herein, a facile, simple and rapid self-assembly of magnetic colloidal nanoparticles (MCNPs) to build magnetically responsive photonic crystals (MRPCs) was devolved. A nonionic amphiphilic random copolymer poly(styrene--vinylpyrrolidone) P(St--VP) with the monomer molar ratio of 1 : 9 was used not only as an emulsifier for miniemulsion self-assembly of FeO magnetic nanoclusters, but also as the coating material on the magnetic nanoclusters through itself assembly. The self-assembly of the magnetic nanocluster and the polymer coating were completed simultaneously without another polymerization process. The characterization of the MCNPs and the optical properties of the MRPCs were investigated in details. TEM showed that the MCNPs had regular spherical structures with an average diameter of 104.6 nm (RSD = 13.9%, = 100). P(St--VP) self-assembly coating was confirmed by IR and XPS, and thermogravimetric analysis showed that the magnetite content was 76.15%. The large content of magnetite and the thin coating of the copolymer gave MCNPs the high saturated magnetization ( ) of 52.60 emu g. Under an external magnetic field, the MCNPs could assemble MRPCs instantaneously and reversibly. The structural color covered entire visible spectrum by tuning the strength of the external magnetic field. On basis of the steric hindrance from neighboring PVP stretching chains, rather than electrostatic repulsion or solvation layer to counterbalance magnetic attraction, the MRPCs could tolerate the electrolyte as high as 0.10 mol L and the variance of pH from 2.0-12.0. The stability of P(St--VP) self-assembly coating was testified through the invariability of the structural color of MRPCs after repeated washing, as well as the recovery of structural color after removing the electrolytes.
在此，我们开发了一种简便、快速的磁性胶体纳米粒子（MCNPs）自组装方法，用于构建磁响应光子晶体（MRPCs）。使用单体摩尔比为1:9的非离子两亲性无规共聚物聚（苯乙烯-乙烯基吡咯烷酮）P（St-VP），不仅作为FeO磁性纳米团簇微乳液自组装的乳化剂，还通过自身组装作为磁性纳米团簇的包覆材料。磁性纳米团簇与聚合物包覆的自组装过程同时完成，无需额外的聚合过程。详细研究了MCNPs的表征和MRPCs的光学性质。透射电子显微镜（TEM）显示，MCNPs具有规则的球形结构，平均直径为104.6 nm（相对标准偏差RSD = 13.9%，n = 100）。通过红外光谱（IR）和X射线光电子能谱（XPS）证实了P（St-VP）的自组装包覆，热重分析表明磁铁矿含量为76.15%。高含量的磁铁矿和共聚物的薄包覆赋予MCNPs高达52.60 emu g的高饱和磁化强度（Ms）。在外部磁场作用下，MCNPs能够瞬间且可逆地组装成MRPCs。通过调节外部磁场强度，结构色覆盖了整个可见光谱。基于相邻聚乙烯吡咯烷酮（PVP）伸展链的空间位阻，而非静电排斥或溶剂化层来平衡磁吸引力，MRPCs能够耐受高达0.10 mol L的电解质以及pH值在2.0 - 12.0之间的变化。通过MRPCs结构色在反复洗涤后不变以及去除电解质后结构色的恢复，证明了P（St-VP）自组装包覆的稳定性。
