This work presented the surface modification of magnetite nanoparticle (MNP) with poly[(t-butyl acrylate)-stat-(poly(ethylene glycol) methyl ether methacrylate)] copolymers (P[(t-BA)-stat-PEGMA])viaa surface-initiated “grafting from” atom transfer radical polymerization (ATRP). Loading molar ratio oft-BA to PEGMA was systematically varied (100 : 0, 75 : 25, 50 : 50, and 25 : 75, resp.) such that the degree of hydrophilicity of the copolymers, affecting the particle dispersibility in water, can be fine-tuned. The reaction progress in each step of the synthesis was monitoredviaFourier transform infrared spectroscopy (FTIR). The studies in the reaction kinetics indicated that PEGMA had higher reactivity than that oft-BA in the copolymerizations. Gel permeation chromatography (GPC) indicated that the molecular weights of the copolymers increased with the increase of the monomer conversion. Transmission electron microscopy (TEM) revealed that the particles were spherical with averaged size of 8.1 nm in diameter. Dispersibility of the particles in water was apparently improved when the copolymers were coated as compared to P(t-BA) homopolymer coating. The percentages of MNP and the copolymer in the composites were determinedviathermogravimetric analysis (TGA) and their magnetic properties were investigatedviavibrating sample magnetometry (VSM).
The surface of magnetite nanoparticle (MNP) was modified with poly(acrylic acid)(PAA)-poly(ethylene glycol) methyl methacrylate (PEGMA) (co)polymer to obtain water dispersible MNP with pH sensitive surfaces via atom transfer radical polymerization (ATRP) of tert-butyl acrylate (t-BA), followed by the t-BA group deprotection. Molar compositions of the (co)polymer were systematically varied, namely 100:0, 75:25, 50:50 and 25:75 of P(t-BA)/PEGMA, respectively, such that the grafting density of carboxylate groups on the MNP surface after the deprotection can be fine-tuned. Transmission electron microscopy (TEM) indicated that the MNP were spherical (ca.5-12 nm in diameter) with some nanoclustering observed. The roles of PAA and PEGMA affecting the hydrodynamic size and zeta potential of the nanocomposites observed via photocorrelation spectroscopy (PCS) were discussed. The percentages of the polymeric composition in the nanocomposites in each step of the reaction were determined via thermogravimetric analysis (TGA) and their magnetic properties were studied via vibrating sample magnetometry (VSM). These novel nanocomposites with pH sensitive surface and magnetically guidable properties might be advantageous for further conjugations either by covalent or ionic bonding with bioentities. HIGHLIGHTS Magnetite nanoparticle (MNP) coated poly(acrylic acid)(PAA)-poly(ethylene glycol) methyl methacrylate (PEGMA) (co)polymer were fabricated via ATRP The ratio of t-BA to PEGMA used in the copolymerization was studied The nanocomposites showed pH sensitive surface and magnetically guidable properties GRAPHICAL ABSTRACT
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