Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System

Abstract

Fluorinated core–shell spheres have been synthesized using a novel semibatch emulsion polymerization protocol employing slow feeding of the initiator. The synthesis results in aqueous dispersions of highly monodisperse spheres bearing a well-defined poly(ethylene glycol) graft (PEGylation). Measurements are consistent with the synthesis achieving a high grafting density that moreover consists of a single PEG layer with the polymer significantly elongated beyond its radius of gyration in bulk. The fluorination of the core of the particles confers a low index of refraction such that the particles can be refractive index matched in water through addition of relatively small amounts of a cosolvent, which enables the use of optical and laser-based methods for studies of concentrated systems. The systems exhibit an extreme stability in NaCl solutions, but attractions among particles can be introduced by addition of other salts, in which case aggregation is shown to be reversible. The PEGylated sphere dispersions are expected to be ideally suited as model systems for studies of the effect of PEG-mediated interactions on, for instance, structure, dynamics, phase behavior, and rheology.

A combined 3D and 2D light scattering study on aqueous colloidal model systems with tunable interactions

“…The PEGylated fluorinated particles were prepared by surfactant free emulsion polymerization, following the procedure given in ref. 36. In a typical synthesis, 1000 mL H 2 O are deoxygenated three times in a 3 L three-necked round bottom flask by firstly applying a vacuum and afterwards flooding with nitrogen.…”

“…We prepared FBMA latex particles which are charge stabilized in aqueous media and which are additionally stabilized sterically by chemically attached PEG chains, according to a semi-batch emulsion polymerization procedure. 36 Electrophoresis measurements using a Malvern Zetasizer 2000, show that the particles behave as charged spheres at low ionic strengths with a zeta potential of À30 mV. The density of particles was determined to be 1.5266 g mL À1 with a density meter (Anton Paar DMA 4500).…”

“…Continued effort has made it possible to synthesize particles with a single and well-defined PEG layer. 36 Moreover, this system bridges fundamental research to life science application, as PEG is a biocompatible material and e.g. PEGylation has already been widely used for drug delivery applications.…”

Synthesis of Sub‐100 nm Glycosylated Nanoparticles via a One Step, Free Radical, and Surfactant Free Emulsion Polymerization

“…diameters under 100 nm using "surfactant free" controlled radical polymerization. [2,[19][20][21][22][23][24][25] One such technique is reversible addition-fragmentation chain transfer emulsion polymerization, in which a short amphiphilic di-block copolymer is prepared, then suspended in water to act as a surfactant for the emulsion polymerization. The initial di-block subsequently becomes bound to the resulting latex particle via chain extension, conveniently imparting functionality from the hydrophilic section onto the resulting latex and avoiding the need for dialysis.…”

“…However, particles made using a surfactant must then be extensively dialyzed to remove the surfactant for use in applications such as drug delivery and photonics . There has therefore been a large amount of research into synthesizing functional nanoparticles with diameters under 100 nm using “surfactant free” controlled radical polymerization . One such technique is reversible addition‐fragmentation chain transfer emulsion polymerization, in which a short amphiphilic di‐block copolymer is prepared, then suspended in water to act as a surfactant for the emulsion polymerization.…”