Thermosensitive Hairy Hybrid Nanoparticles Synthesized by Surface-Initiated Atom Transfer Radical Polymerization

Abstract

This article reports on the synthesis of thermosensitive polymer brushes on silica nanoparticles by atom transfer radical polymerization (ATRP) and the study of thermo-induced phase transitions in water. Silica nanoparticles were prepared by the Stöber process and the surface was functionalized by an ATRP initiator. Surface-initiated ATRPs of methoxydi(ethylene glycol) methacrylate (DEGMMA) and methoxytri(ethylene glycol) methacrylate (TEGMMA) were carried out in THF at 40 degrees C in the presence of a free initiator, benzyl 2-bromoisobutyrate. The polymerizations were monitored by 1H NMR spectroscopy and gel permeation chromatography. The hairy hybrid nanoparticles were characterized by thermogravimetric analysis and scanning electron microscopy, and the thermoresponsive properties were investigated by variable temperature 1H NMR spectroscopy and dynamic light scattering. The cloud points of free poly(DEGMMA) and poly(TEGMMA) in water were around 25 and 48 degrees C, respectively. The thermo-induced phase transitions of polymer brushes on silica nanoparticles began at a lower temperature and continued over a broader range (4-10 degrees C) than those of free polymers in water (< 2 degrees C).

Toward Greener Nanosynthesis

“…Candidates for postsynthetic modifications are generally produced by direct synthesis (ω-functionalized particles created by Brust preparations) or sometimes ligand exchange methods (usually involving the introduction of a ligand bearing a reactive pendant functional group). Modification reactions include polymerizations, [213][214][215][216] coupling reactions, 40,48,[217][218][219][220][221] or transformation of an existing chemical moiety. 48,[222][223][224] In all cases, the success of such modifications relies not only on the nanoparticles' tolerance for various reaction conditions but also on the overall reactivity and steric environment presented by functional groups that are constrained through binding to a nanoparticle.…”

Thermo‐Switchable Materials Prepared Using the OEGMA‐Platform

“…Zhao and co-workers studied the modifi cation of model silica particles (Figure 2 ). [ 75 ] The thermoresponsive polymer shells allowed a nearly quantitative thermo-induced transfer of the particles from aqueous to organic phase. [ 76 ] Comparable results were afterwards reported by Wang and co-workers with OEGMA-modifi ed gold particles (Figure 2 ).…”

Dispersion of polymer-grafted magnetic nanoparticles in homopolymers and block copolymers

“…Traditionally, coupling agents or surfactants have been widely used to stabilize the NPs [15,16]. More recently, ''grafting to'' and ''grafting from'' techniques have become popular methods to modify NPs with polymer brushes [17][18][19][20][21][22][23][24][25][26].…”