From the Unimolecuclar Template of Water-Soluble Multiarm Star Brush Copolymers to One-Dimensional Colloidal Nanocrystal Clusters: Facile Synthesis via a Combination of Magnetic Assembly with Photoind

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• 作者：Junjing Bai ; Xiaobing Wang ; Peng Fu ; Zhe Cui ; Qingxiang Zhao ; Xinchang Pang ; Minying Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 14, 2016
• 年：2016
• 卷：120
• 期：1
• 页码：705-714
• 全文大小：571K
• ISSN：1932-7455

文摘

An effective process for the fabrication of one-dimensional (1D) colloidal superparamagnetic magnetite (Fe₃O₄) nanocrystal clusters was developed by combining magnetic assembly and photoinduced cross-linking under an external magnetic field. First, a series of water-soluble multiarm star brush copolymers with different molecular weights using α-cyclodextrin as a multifunctional initiator, star brush copolymer PEO-g-PAA, which consisted of poly(ethylene oxide) (PEO) as the main chain and poly(acrylic acid) (PAA) as functional side chains, were prepared by combining anionic ring-opening copolymerization with atom transfer radical polymerization (ATRP). Sequentially, star brush copolymer PEO-g-PAA as a spherical unimolecuclar template was utilized to structure-direct the in situ formation of spherical superparamagnetic Fe₃O₄ colloidal nanocrystal clusters by loading precursors of Fe₃O₄ (FeCl₃ and FeCl₂) into the PAA compartment. Surface-tethered PAA grafting chains of spherical Fe₃O₄ colloidal nanocrystal clusters, produced by ATRP, retain terminal bromine atoms that were subsequently converted into photo-cross-linkable azide groups (-N₃) through nucleophilic substitution. The spherical Fe₃O₄ colloidal nanocrystal clusters coated with photo-cross-linkable azide groups were assembled into temporary 1D secondary nanostructures by being exposed to external magnetic fields. The resulting temporary 1D nanoclusters were efficiently cross-linked by exposure to UV light to stabilize the 1D secondary nanostructures of Fe₃O₄ nanocrystals. The dimension of the resulting stable and cross-linked 1D clusters can be tuned by adjusting the strength of the external magnetic field.