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This work describes a versatile method to encapsulate graphene oxide (GO) with polymers using reversible addition-fragmentation chain transfer (RAFT) mediated emulsion polymerization. A living low molecular weight anionic macro-RAFT statistical copolymer of sodium styrene sulfonate, acrylic acid, and butyl acrylate (BA) was synthesized using 2-{[(butylsulfanyl)carbonothioyl] sulfanyl} propanoic acid as the chain transfer agent. GO was dispersed in water by pretreating the surface with poly(allylamine hydrochloride) (PAH), before being stabilized by the addition of the anionic macro-RAFT copolymer. PAH was used to facilitate the adsorption of the macro-RAFT copolymer to the GO surface via electrostatic attraction between opposite charges. The dispersed GO sheets were encapsulated with polymer by the free radical emulsion polymerization of methyl methacrylate and BA under starved fed conditions. The polymer shells encapsulating the GO sheets were formed by the chain extension of the adsorbed living macro-RAFT copolymer. TEM, SEM, FTIR, and AFM were used to confirm the presence of the polymer layer on the surface of the GO. The thickness of the polymer coating can be adjusted by controlling the amount of monomer fed into the system. Partial polymer coatings of the GO could be achieved by varying the amount of PAH. The encapsulated GO was found to be easily dispersed in both aqueous and organic solvents over a range of polarities. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1413–1421

In this study, we propose an alternative method to produce high solids, micrometer-sized polystyrene (PS) latexes with narrow size distribution, based on the use of large amounts of polymerization initiator and allowing the presence of oxygen in the reaction vessel. We have demonstrated that the deoxygenation of the reaction mixture in surfactant-free emulsion polymerization becomes redundant if enough radical initiator is employed, and that particles with narrow size distribution can be obtained in the presence or absence of oxygen. The significance of this method lies in its simplicity and robustness: the method requires only a single-neck flask sealed with a rubber septum, a magnetic stirrer, and an oil bath. We also show that the use of large amounts of radical initiator allows the preparation of latexes with particularly high solid contents (up to 20 wt %), which is uncommon in systems with no added stabilizing agent.

In this work, successful polymer coating of COOH-functionalized multiwalled carbon nanotubes (MWCNTs) via reversible addition fragmentation chain transfer (RAFT) mediated emulsion polymerization is reported. The method used amphiphilic macro-RAFT copolymers as stabilizers for MWCNT dispersions, followed by their subsequent coating with poly(methyl methacrylate-co-butyl acrylate). Poly(allylamine hydrochloride) was initially used to change the charge on the surface of the MWCNTs to facilitate adsorption of negatively charged macro-RAFT copolymer onto their surface via electrostatic interactions. After polymerization, the resultant latex was found to contain uniform polymer-coated MWCNTs where polymer layer thickness could be controlled by the amount of monomer fed into the reaction. The polymer-coated MWCNTs were demonstrated to be dispersible in both polar and nonpolar solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

We demonstrate the ability of the reversible addition-fragmentation chain transfer (RAFT) process to produce well-defined block co-oligomers for which each block has a narrow molecular weight distribution and degrees of polymerization ranging from 2 to 33. We exploit RAFT versatility to control the structure of the co-oligomers and produce amphiphilic block co-oligomers of styrene, acrylic acid and ethylene glycol. A detailed study shows that the amphiphilic diblock co-oligomers self-assemble in solution and form micelles or particles, depending on the hydrophobicity of the diblock. These oligomers present an excellent alternative to traditional amphiphilic molecules, by combining the properties of polymers with those of single molecule surfactants.

In this work, successful synthesis of polymer nanorattles containing titanium dioxide pigment particles in the centers of air voids is reported. The method used amphiphilic macro-RAFT copolymers as stabilizers for pigment dispersion and the subsequent encapsulation of the pigment with polymer. The particles were first encapsulated by a water swellable hydrophilic layer, followed by a hard hydrophobic layer. Nanorattles were formed by swelling of hydrophilic polymer layers on the surface of the encapsulated pigment particles in a basic solution at elevated temperature. After swelling, the outer hard polymer shell was crosslinked to improve its strength. Air void sizes of the nanorattles were found to be controlled by swelling time, temperature, and the hydrophilic polymer layer thickness. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The diffusion coefficients are reported of rubbery ternary systems consisting of the polymer, its monomer analogue (i.e., the saturated equivalent of the monomer), and trace quantities of oligomers (dimer, trimer, tetramer and hexamer) for 2-hydroxyethyl methacrylate (HEMA). These have been obtained with pulsed-field-gradient NMR spectroscopy with a polymer weight fraction (f(p)) of 0 less than or equal to fp less than or equal to 0.4. The oligomers are macromonomers synthesized with a cobalt catalytic chain-transfer agent. The diffusion coefficients are about an order of magnitude smaller than those for monomers such as methyl methacrylate; this effect is ascribed to hydrogen bonding in HEMA. The diffusion coefficient D-i of an i-meric oligomer has been fitted with moderate accuracy by an empirical universal scaling relation, D-i(f(p))/D-1(f(p)) approximate to i(-(0.66?)), previously found to provide an adequate fit to corresponding data for styrene and for methyl and butyl methacrylates. The approximate empirical scaling relation seems to hold for a remarkably wide range of types of monomer/polymer systems. These results are of use in modeling rates and molecular weight distributions in free-radical polymerization, particularly for termination (which is chain-length-dependent and is controlled by the diffusion coefficient of chains of the low degrees of polymerization studied here). (C) 2003 Wiley Periodicals, Inc.