Poly(glycerol monomethacrylate)–Poly(benzyl methacrylate) Diblock Copolymer Nanoparticles via RAFT Emulsion Polymerization: Synthesis, Characterization, and Interfacial Activity

Victoria J Cunningham,Graham J Leggett,Osama M Musa,Kate L Thompson,Abdullah M Alswieleh,Steven P Armes,Mark Williams

doi:10.1021/ma501140h

Abstract

A poly(glycerol monomethacrylate) (PGMA) macromolecular chain transfer agent has been utilized to polymerize benzyl methacrylate (BzMA) via reversible addition–fragmentation chain transfer (RAFT)-mediated aqueous emulsion polymerization. This formulation leads to the efficient formation of spherical diblock copolymer nanoparticles at up to 50% solids. The degree of polymerization (DP) of the core-forming PBzMA block has been systematically varied to control the mean particle diameter from 20 to 193 nm. Conversions of more than 99% were achieved for PGMA51–PBzMA250 within 6 h at 70 °C using macro-CTA/initiator molar ratios ranging from 3.0 to 10.0. DMF GPC analyses confirmed that relatively low polydispersities (Mw/Mn < 1.30) and high blocking efficiencies could be achieved. These spherical nanoparticles are stable to both freeze–thaw cycles and the presence of added salt (up to 0.25 M MgSO4). Three sets of PGMA51–PBzMAx spherical nanoparticles have been used to prepare stable Pickering emulsions at variou...

Highlights

Conventional aqueous emulsion polymerization requires a water-immiscible monomer, a water-soluble initiator, surfactant and water
poly(glycerol monomethacrylate) (PGMA) has been previously deployed as a reactive steric stabilizer for the synthesis of diblock copolymer nanoparticles via reversible addition−fragmentation chain transfer (RAFT) aqueous dispersion polymerization.[36−38] In particular, a PGMA macro-CTA was chain-extended with a watermiscible monomer, 2-hydroxypropyl methacrylate (HPMA)
The growing water-insoluble PHPMA block led to Polymerization-induced self-assembly (PISA), which in turn produced a wide range of diblock copolymer morphologies, including spheres, worms, jellyfish, octopi and vesicles.[39]

Summary

■ INTRODUCTION

Conventional aqueous emulsion polymerization requires a water-immiscible monomer, a water-soluble initiator, surfactant and water. Hawkett et al developed the first successful ab initio RAFT emulsion polymerization using a poly(acrylic acid) macromolecular chain transfer agent (macro-CTA), which was chain-extended using n-butyl acrylate to form stable latex particles.[12−14] This formulation was further developed to produce ABC triblock copolymers by the addition of styrene as the third block.[15]. Two PGMA macro-CTAs have been chain-extended using a waterimmiscible monomer, benzyl methacrylate (BzMA), via RAFT aqueous emulsion polymerization, see Figure 1. The phenylboronic acid-functionalized wafers were immersed in a 0.01% w/w aqueous dispersion of fluorescently-labeled PGMA51−PBzMA100 nanoparticles at either pH 4 or pH 10 for 2 h at 20 °C. The molecular weights and polydispersities of the PGMA macro-CTA and PGMA−PBzMA diblock copolymers were determined by DMF GPC at 60 °C. For the sake of brevity “G” denotes PGMA and “B” denotes PBzMA.) bMonomer conversion determined by 1H NMR spectroscopy. cDetermined by DMF GPC using a series of near-monodisperse poly(methyl methacrylate) calibration standards

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ REFERENCES