Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)

Abstract

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

A controlled approach to iron oxide nanoparticles functionalization for magnetic polymer brushes

“…Even though not many comparable data are available in the literature on this point, these densities are relatively high comparing to similar studies reported. In particular, Garcia [20], and Babu and Dhamodhran obtained 2.0 molecules/nm 2 for a phosphonic acid terminated ATRP initiator [21]. This confirms that the optimization of reaction conditions can lead to an increase in graft density.…”

Synthesis of Polymer Grafted Magnetite Nanoparticle with the Highest Grafting Density via Controlled Radical Polymerization

“…One way of testing this hypothesis is to study the grafting density of surface-initiated ATRP, involving monomers with varying rate of propagation. Therefore, we choose to study the grafting density of surface-initiated ATRP involving three different monomers, viz., benzyl methacrylate, styrene, and methyl methacrylate [41]. The results from these study are summarized below.…”

“…The synthesis of magnetite nanoparticles as well as the ATRP initiator, 2-bromo-2-methyl-propionic acid 2-phosphonooxy-ethyl ester ( 1 ) and its anchoring to the magnetite nanoparticle to get ATRP initiator immobilized magnetite nanoparticle ( 2 ) has been reported by us in the literature [41]. …”

“…In comparison, the ambient temperature ATRP of methyl methacrylate from a phosphonic acid anchored magnetite surface results in a grafting density of an initiator 1 chain/nm 2 for an initiator grafting density of 2 molecules/nm 2 . Thus 50% of the surface initiating groups on the magnetite surface participated in the polymerization [41]. This was carried out without sacrificial initiator as well as without the initial addition of Cu(II).…”

“…In order to explore this hypothesis in detail, we have chosen monomers that polymerize faster as well as slower in comparison with methyl methacrylate and report the results obtained. In this work, the ATRP of benzyl methacrylate at ambient temperature as well as that of styrene at 100 °C is carried out from the magnetite nanoparticle surface, without using the sacrificial initiator [42] to compare its grafting density with that of methyl methacrylate, which was polymerized from the surface of MNs, at ambient temperature [41]. Surface-Initiated polymerization without the use of sacrificial initiator could offer certain advantages such as the elimination of the step associated with the removal of unattached polymer that is formed from the sacrificial initiator.…”