A Comparative Study of Chemical Routes for Coating Gold Nanoparticles via Controlled RAFT Emulsion Polymerization

Abstract

The synthesis of core‐shell Au nanoparticles protected by an amphiphilic block copolymer is investigated by distinct reversible addition fragmentation chain transfer (RAFT) emulsion polymerization routes. The controlled polymerization of polymer shells onto Au nanoparticles is attempted by using the macroRAFT (MR) agent based on 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid synthesized via RAFT polymerization of poly(ethylene glycol) methyl ether acrylate and exploring several approaches, which include (i) post‐modification; (ii) in situ synthesis and (iii) “grafting from” strategies. In the conditions investigated here all these strategies lead to Au polymer nanocomposites but morphological well‐defined core‐shell nanoparticles are only obtained by applying the “grafting from” strategy. In particular, conditions that promote chain extension from the MR agent adsorbed onto the Au nanoparticles are found necessary to obtain nanostructures with such morphological characteristics and that still show the localized surface plasmon resonance typical of colloidal Au nanoparticles.

Biofunctional Polymer Coated Au Nanoparticles Prepared via RAFT-Assisted Encapsulating Emulsion Polymerization and Click Chemistry

“…In this case, only 34% conversion was reached after 24 h; see Figure S2B in Supporting Information . When comparing the results obtained using VA-044 at 70 °C with those obtained using ACPA also at 70 °C in our previous studies [ 15 , 16 ], it is striking to observe that 81% monomer conversion was only obtained after 4 h of reaction, when the latter was used as an initiator. Differences in the rate of polymerization using ACPA and VA-044 at 70 °C were previously reported by Perrier et al [ 32 , 33 ] and are due to the fact that VA-044 has a higher decomposition rate coefficient ( k d ) which allows increasing the rate of the polymerization reaction without affecting its livingness.…”

“…This was further supported by the fact that azides can undergo cycloaddition reactions with the double bonds of methyl methacrylate monomers [ 31 ]. As in our previous studies, the encapsulation of Au NPs via REEP was carried out at 70 °C using ACPA as the initiator [ 15 , 16 ], and the effect of temperature on VA-044 on the polymerization of the hydrophobic monomers via RAFT emulsion polymerization was first studied in the absence of Au NPs.…”

“…For comparative purposes, chain extension of the macroRAFT P(PEGA 40 )-TTC was first carried out via RAFT emulsion polymerization at 70 °C using VA-044 as the initiator. The polymerization conditions, [macroRAFT]/[initiator] and [monomer]/[macroRAFT] ratios, were kept the same as in our previous work where ACPA was used as the initiator [ 16 ] as well as the mixture of hydrophobic monomers methyl methacrylate (MMA) and butyl acrylate (BA) (10:1 w / w ) [ 15 ]. As expected, monomer conversion was much higher when VA-044 was used.…”

“…Since then, chemical and morphological distinct inorganic cores have been encapsulated, such as carbon nanomaterials, CdS, PbS, CeO 2 , SiO 2 , montmorillonite, and SiO 2 @Gd 2 O 3 :Eu 3+ [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The use of REEP to encapsulate colloidal gold nanoparticles (Au NPs) with an average diameter of 15 nm has also been explored due to its potential applications in biosensing [ 15 , 16 ]. Au NPs exhibit localized surface plasmon resonances (LSPR) that are sensitive to the size, shape, and the surrounding environment (such as interparticle interaction and surface modification).…”

“…Following our previous works on the encapsulation of Au NPs via REEP at 70 °C [ 15 , 16 ], we decided to investigate the combination of REEP and click chemistry in order to prepare biofunctional polymer@Au NPs with core–shell structures. As such, azide-polymer@Au NPs have been prepared using REEP at 44 °C and subsequently functionalized with biotin via click chemistry.…”