Synthesis of Polymer Brush in Oil-Phase through Photo-Emulsion Polymerization

Oil-dispersed spherical polymer brush consisting of a hydrophilic core and lipophilic shell was synthesized through a novel “grafting from” procedure. Poly(acrylic acid) (PAA) nanoparticles with an average diameter of 100 nm were firstly prepared in toluene by inverse emulsion polymerization. At the end of polymerization, photo initiator 2[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol- methacrylate (HMEM) was slowly added to copolymerize at the surface of PAA nanoparticles. After the addition of N-vinyl carbazole monomer, poly(N-vinyl carbazole) (PVK) chains finally generated from the surface of PAA core to form a brush-like structure via photo-emulsion polymerization under the irradiation of UV light. Dynamic light scattering (DLS) results display an increase in hydrodynamic diameters after photo-emulsion polymerization. In addition, the characteristic peaks of PVK were clearly observed in UV-vis spectra and photoluminescence spectra, indicating PVK chains were grafted onto PAA matrix. Transmission electron microscopy (TEM) shows the spherical shape of PAA-PVK brushes with relatively narrow size distribution. Compared with pure PAA core, the stability of PVK grafted PAA brush was significantly improved in organic solvent. This kind of novel core-shell structure is promising in the field of fluorescence labeling carrier and protein encapsulation in non-aqueous media.