Encapsulation of titanium dioxide in styrene/n‐butyl acrylate copolymer by miniemulsion polymerization

Abstract

Miniemulsion copolymerization of styrene/ n-butyl acrylate was investigated as a means of encapsulating hydrophilic titanium dioxide (TiO 2 ) in a film-forming polymer. Dispersion studies of the TiO 2 were first carried out to determine the choice of stabilizer, its concentration, and the dispersion process conditions for obtaining stable TiO 2 particles with minimum particle size. Through screening studies of various functional stabilizers and shelf-life stability studies at both room and polymerization temperatures, Solsperse 32,000 was selected to give relatively small and stable TiO 2 particles at 1 wt % stabilizer and with 20 -25 min sonification. The subsequent encapsulation of the dispersed TiO 2 particles in styrene/n-butyl acrylate copolymer (St/BA) via miniemulsion polymerization was carried out and compared with a control study using styrene monomer alone. The lattices resulting from the miniemulsion encapsulation polymerizations were characterized in terms of the encapsulation efficiencies (via density gradient column separations; DGC) and particle size (via dynamic light scattering). Encapsulation efficiencies revealed that complete encapsulation of all of the TiO 2 by all of the polymer was not achieved. The maximum encapsulation efficiencies were 79.1% TiO 2 inside 61.7% polystyrene and 63.6% TiO 2 inside 38.5% St/BA copolymer. As the density of the particles collected from the DGC increased from one layer to another, both the average particle size and the number of the TiO 2 particles contained in each latex particle increased.

Preparation and characterization of poly(MMA–BA)/nano-ATO hybrid latex via miniemulsion polymerization

“…Monomer droplet nucleation becomes predominant in miniemulsion, and each droplet can be considered as an independent ''nanoreactor.'' 7 Miniemulsion polymerization has become a convenient one-step nanoencapsulation method, attributable to the special nucleation mechanism, which has been widely used in the encapsulation of inorganic nanoparticles, such as silica, [8][9][10][11][12] titanium dioxide, [13][14][15] Fe 3 O 4 , [16][17][18][19][20] and alumina. 21 However, there is no report so far of this method having been used to encapsulate nano-ATO with polymer.…”

Synthesis of PEG-PCL-based polyurethane nanoparticles by miniemulsion polymerization

“…In principle, polymerization occurs in submicrometric droplets allowing the encapsulation of different compounds via step or chain polymerizations. As reported by Tiarks and Landfester (2001) [19], when PU nanoparticles are prepared by direct oil in water miniemulsion polymerization two reaction paths may occur: 1) polyaddition of isocyanate with the polyol to form urethane and 2) hydrolysis of isocyanate to form urea with CO 2 release [18]. This second reaction path results in a loss of stoichiometry, as well as to the formation of polymers with a lower molar mass and thus, is usually sought to be minimized [10], [11], [20] and [21].…”

“…Miniemulsion is defined as dispersions of relatively stable oil droplets with a size range from 50 to 500 nm, prepared by shearing a system containing oil, water, surfactant and costabilizer [17] and [18]. In principle, polymerization occurs in submicrometric droplets allowing the encapsulation of different compounds via step or chain polymerizations.…”

Morphology and kinetic mechanism of facile one-step preparing TiO2/polyacrylate/TiO2multilayer core–shell hybrid emulsion via miniemulsion polymerization

“…Recently, there is some research on the preparation of nano-TiO 2 /polymer core-shell hybrid emulsion via miniemulsion polymerization. [28][29][30] To the best of our knowledge, one cannot obtain TiO 2 /polymer/TiO 2 multilayer core-shell structure via one miniemulsion polymerization in the current literature. What is more, the existence of inorganic nanoparticles leads to complicated interactions between nanoparticles, monomers, emulsifiers, and initiator.…”