New Route to Amphiphilic Core−Shell Polymer Nanospheres: Graft Copolymerization of Methyl Methacrylate from Water-Soluble Polymer Chains Containing Amino Groups

Abstract

A novel method has been developed to prepare amphiphilic core-shell polymer nanospheres via graft copolymerizations of methyl methacrylate (MMA) from water-soluble polymer chains containing amino groups. Thus, amine-substituted biopolymers and synthetic polymers are treated with a small amount of tert-butyl hydroperoxide (TBHP, 0.08 mM) in water at 80 °C to generate free radicals on the amine nitrogens, which subsequently initiate the graft copolymerization of MMA. tert-Butoxy radicals are also generated that either initiate the homopolymerization of MMA or abstract hydrogen from the polymer backbones. The amphiphilic macroradicals generated in situ self-assemble to form polymeric micelle-like microdomains, which promote the emulsion polymerization of the monomer. Thus, well-defined, amphiphilic core-shell nanospheres, which range from 60 to 160 nm in diameter, are produced in the absence of surfactant. The conversion and grafting efficiency of the monomer strongly depend on the TBHP concentration and the structure of the amino-containing water-soluble polymer. Polymers containing primary amine groups are considerably more effective than those containing secondary or tertiary groups, while ammonium cations do not induce the polymerization. The particle size and stability strongly depend on the structure and molecular weight of the hydrophilic polymer, as well as the pH of the mixture. Transmission electron microscopic (TEM) images of the particles clearly show well-defined core-shell morphologies where PMMA cores are coated with hydrophilic polymer shells. The amphiphilic core-shell nanospheres can be produced in high concentrations (up to 22% solids content). This new method is scientifically and technologically significant because it provides a commercially viable route to a wide variety of novel amphiphilic coreshell nanospheres.

Preparation of block copolymer vesicles in solution

“…That group 110 also investigated the mixing of hydroxyl-containing PS in chloroform and P4VP in nitromethane, followed by crosslinking and core removal by DMF, to produce hollow spheres that were resistant to vacuum drying. Li et al 103 used tert-butyl hydroperoxide to treat amine-substituted biopolymers (e.g., bovine serum albumine (BSA) and gelatin) and synthetic polymers in water in the presence of methyl methacrylate to create graft copolymers that were then used to form 60 -160 nm hollow spheres. Kramer et al 105 constructed core-shell structures from dendritic polymers, polyglycerol and poly-(ethylene imine), by selective and reversible functionalization.…”

Synthesis and characterisation of sterically stabilised polypyrrole particles using a chemically reactive poly(vinyl amine)-based stabiliser

“…Primary amine-based polymers have been examined as reactive steric stabilisers by Li et al for the aqueous emulsion 85 polymerisation of vinyl monomers such as styrene, n-butyl acrylate or methyl methacrylate [19,20]. In this case, the judicious selection of a suitable free radical initiator (e.g.…”

Polyethylenimine-Based Amphiphilic Core–Shell Nanoparticles: Study of Gene Delivery and Intracellular Trafficking

“…The PMMA-PEI amphiphilic core-shell nanoparticles were prepared according to our previously described method [25]. After polymerization, the crude particle dispersion was purified through repeated centrifugations and decantations with de-ionized water until the conductivity of the supernatant was similar to that of the water used.…”

“…The PMMA-PEI amphiphilic core-shell nanoparticles were prepared according to our previously described procedures [25]. Methyl methacrylate (MMA) monomer was polymerized with cationic branched PEI (25 kDa) in a weight ratio of 1:2.…”

“…To address the PEI cytotoxicity problem and enhance gene transfection efficiency, we have previously designed a novel type of amphiphilic core-shell nanoparticle that is composed of a poly(methyl methacrylate) (PMMA) core and a branched PEI shell for gene delivery [25,26]. The PMMA-PEI nanocarrier is spherical in shape, monodisperse in aqueous medium and has a well-defined core-shell nanostructure with a highly extended PEI shell in water.…”