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Issue 24, 2014
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Optimization of the RAFT polymerization conditions for the in situ formation of nano-objects via dispersion polymerization in alcoholic medium

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Abstract

Hydrophilic polymer brushes based on poly(ethylene glycol) methyl ether acrylate (P(PEGA454)) or poly(ethylene glycol) methyl ether methacrylate (P(PEGMA475)), both having a trithiocarbonate end group, were prepared in water–dioxane (9 : 1) at 44 °C via RAFT polymerization, and subsequently used in RAFT dispersion polymerization of styrene in isopropanol at 90 °C. RAFT reaction conditions were first optimized to prepare P(PEGA454) and P(PEGMA475) macro-RAFT agents at high monomer conversions (>90%) and very low fraction of dead chains (<1%). The macro-RAFT agents were then shown to have similar efficiency in terms of reinitiating and controlling the polymerization of styrene in dispersion polymerization. Both polymer brushes allowed the preparation of well-defined amphiphilic diblock copolymers (P(PEGA454)-b-PS and P(PEGMA475)-b-PS) which self-assemble in situ into nano-objects with various morphologies. Using relatively long chain P(PEGA454) or P(PEGMA475) macro-RAFT agents (DP ≈ 75) leads to the formation of near uniform spherical nano-particles with diameters ranging from 30 to 140 nm, depending on the targeted DP of the PS block. In contrast, TEM and DLS studies demonstrated that using a shorter P(PEGA454) or P(PEGMA475) macro-RAFT agent (DP ≈ 20) enables the formation of worm-like micelles, vesicles and large compound vesicle morphologies, in addition to spheres. Cryo-TEM was used to confirm polymerization induced morphology transition, rather than morphologies obtained via self-assembly driven by selective solvent or solvent evaporation during the preparation of samples for characterization.

Graphical abstract: Optimization of the RAFT polymerization conditions for the in situ formation of nano-objects via dispersion polymerization in alcoholic medium

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Publication details

The article was received on 19 Jun 2014, accepted on 28 Aug 2014 and first published on 28 Aug 2014


Article type: Paper
DOI: 10.1039/C4PY00855C
Citation: Polym. Chem., 2014,5, 6990-7003
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    Optimization of the RAFT polymerization conditions for the in situ formation of nano-objects via dispersion polymerization in alcoholic medium

    W. Zhao, G. Gody, S. Dong, P. B. Zetterlund and S. Perrier, Polym. Chem., 2014, 5, 6990
    DOI: 10.1039/C4PY00855C

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