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The dispersion of magnetic nanorods in poly(2-vinylpyridine)

Authors


Correspondence to: Chieh-Tsung Lo, Department of Chemical Engineering, National Cheng Kung University, 1 University Road, Tainan City 701, Taiwan. E-mail: tsunglo@mail.ncku.edu.tw

Abstract

The dispersion of magnetic nanorods in poly(2-vinylpyridine) (PVP) as a function of rod length, particle loading and molecular weight of PVP was investigated. The nanorods were organized into small spherical clusters at low particle loading. Further increasing the particle concentration caused an increase in the size of the aggregates. Additionally, the internal structure of the nanorods developed into a raft-like structure, forming rectangular clusters. The incorporation of longer nanorods in the PVP amplified the magnetic interaction energy, which created conditions to induce extensive aggregation. The entanglement of the polymer also played an important role in the arrangement of the nanorods. This behavior could be categorized into two regimes, MPVP > Me and MPVP < Me, where MPVP and Me are the number-average molecular weight and entanglement molecular weight of PVP, respectively: for MPVP > Me, PVP formed entanglements that prevented nanorods from extensive aggregation; for MPVP < Me, PVP could not form entanglements, and nanorods could move freely in the PVP, and thus significant rod aggregation occurred. Simple calculations to assess the contribution of the magnetic interaction, the van der Waals interaction and the free energy of mixing of the system to the arrangement of magnetic nanorods in the homopolymer are discussed. © 2013 Society of Chemical Industry

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