Tunable morphology for silica/poly(acrylic acid) hybrid nanoparticles via facile one-pot synthesis

Double in Situ Preparation of Raspberry-like Polymer Particles

Well-defined raspberry-like poly(styrene- co-4-vinylpyridine)-SiO₂ nanocomposite particles with a diameter of around 200 nm were easily prepared by a double in situ process in nanoemulsion with the water-soluble dye Eosin Y as the stabilizer. During radical polymerization of the nanodroplets comprising styrene, 4-vinylpyridine (4-VP), and tetraethoxysilane (TEOS), the silane phase is expelled from the polymer phase to the oil/water (o/w) interface. In the later polymerization stage, SiO₂ nanoparticles with a size of around 25 nm were produced via the in situ sol-gel reaction of TEOS at the o/w interface promoted by the negatively charged dye. The pyridine moieties in the copolymer fix the SiO₂ nanoparticles on the surface of the polymer particles by electrostatic interactions without any sign of free unbound silica particles as proven by transmission electron microscopy.

The effect of tunable morphology on the potential application of p(acrylic acid-co-2-ethylhexyl acrylate)/silica nanohybrids

The present study deals with the one-pot synthesis of acrylate copolymers/silica latexes through the use of simultaneous radical polymerization of acrylic monomers and a silica sol-gel precursor. In presence of 3-methacryloxypropyltrimethoxysilane (γ-MPS) and 3-aminopropyltriethoxysilane (APTS), compatibility of acrylate chains to the silica species was improved by the chemical bonds as revealed by Fourier transform infrared spectroscopy (FTIR) analysis. Transmission electron microscopy (TEM) demonstrated the successful formation of p(acrylic acid-co-2-ethylhexyl acrylate)/silica nanohybrids with core-shell morphology. The nanohybrids have been used to modify a glassy carbon electrode (GCE). Cyclic voltammetry and electrochemical impedance spectra were utilized to investigate the properties of the modified electrode in a 1.0 m KCl solution that contained 1.0 mm K4[Fe(CN)6]/K3[Fe(CN)6], and the interface properties of electrode surfaces. The result showed a dramatic decrease in redox activity as compared to the bare GCE electrode. This revealed a slight increase in electron transfer resistance and the conductivity of the copolymer oligomers and silica species in the hybrid nanostructure. All the electrochemical results illustrated that the p(acrylic acid-co- 2-ethylhexyl acrylate)/silica nanohybrids could immobilize the selective analytes on the electrodes, which had electrochemical catalytic activity. The barrier properties of the hybrid films were also examined via ultraviolet (UV) absorption capacity of the films. It could be concluded that the adsorption capacity was a function of the silica content and uniform dispersion of the nanoparticles in the resultant films.