Polystyrene latex, transmission electron microscopy

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

The transmission electron microscopy results are consistent with a segregated latex particle consisting of a polystyrene rich core and a soft poly-n-butyl acrylate rich shell. 

Aniline was added to a monodisperse cationic polystyrene latex and polymerisation initiated by the addition of ammonium persulphate solution, forming a core-shell latex, which was characterised by infrared spectroscopy, and scanning and transmission electron microscopy. The composites exhibited electrical conductivity comparable to that of pure polyaniline, with a percolation threshold of approximately 3 wt% polyaniline. 12 refs. 

Figure 5.12 Scaling law time dependence for two polystyrene latexes. The H135 material was composed of latexes of 325,000 g/mol polymer having hydrogen end groups. The SI35 material had —SO3 groups at the end of each molecule, with a molecular weight of 325,000 g/mol also. Particle sizes by transmission electron microscopy were in the range of 100-120 nm in all cases. Measurements were by SANS on samples annealed for interdiffusion at 135°C (79).

The hyperbranched PILs represent effective stabilizers in heterogeneous polymerization reactions. When employing water-soluble PEHO-ClImOTs as the emulsifier in the 2,2 -azobis(2-methylpropionitrile) (AIBN) initiated mini-emulsion polymerization of styrene, stable polystyrene (PS) latexes were obtained. Characterization by means of transmission electron microscopy (TEM) indicated the presence of spherical PS nanoparticles (see Figure 7.5). Further studies revealed that, by modifying parameters such as the PIL/monomer ratio and the duration of the ultra-sonication treatment prior to the polymerization, the mean diameter of the obtained PS particles can be varied from 40 nm to 110 nm. In contrast to PEHOClImOTs, the use of the low-molecular-weight ILs 1,3-dimethylimidazolium tosylate or 1-butyl-3-methylimidazolium tosylate did not result in the formation of stable latexes. 

Visualization of the QDs within the latex particles is the most reliable proof of their existence. Transmission electron microscopy [TEM] micrographs of certain polystyrene latexes prepared are shown in Figure 6.19. 

Figure 4.48. Transmission electron microscopy micrographs of freeze dried polystyrene latex (A) used as a control for the experiment shows three dimensional particles with no deformation, whereas an air dried film forming latex (B) shows flat regions that have no shadow. The same latex as in (B) after freeze drying is clearly three dimensional, based on the shadows present (C).

Transmission and scanning electron microscopy, differential scanning calorimetry and minimum film temperature analysis supports a core/shell morphology for the two-stage latex polymers, consisting predominantly of a polystyrene rich core surrounded by a soft acrylic rich shell. 

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