Poly 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. 

Peculiar DNA architecture was demonstrated in 25% aqueous ethanol when DNA was complexed with series of cationic detergents in the presence of poly(glutamic acid) [124]. Electron microscopy and x-ray scattering demonstrated that DNA can pack cetyltrimethylammonium bromide molecules into rodlike micelles, which form a hexagonal lattice. Interestingly, circular dichroism spectroscopy revealed that in these complexes DNA adopts left-handed conformation. 

In order to obtain Pt nanoparticles, aqueous solution of 10 M K2PtCl4, which contained 10 M (as monomer unit) of poly-NIPA or poly-NEA, was bubbled with Ar gas and then H2 gas. Then the reaction vessel was sealed tightly and kept in a water bath at a suitable temperature. At given reaction times, the vessels were opened and the samples for transmission electron microscopy (TEM) were prepared by soaking a grid (carbon substrate, Oken) in the colloidal solution and then drying it in the air. The TEM (Hitachi H-8100) was operated at 200 kV. 

Recently, Kroeze et al. prepared polymeric iniferter 34 including poly(BD) segments in the main chain [152]. They successfully synthesized poly(BD)-block-poly(SAN), which was characterized by gel permeation chromatography, elemental analysis, thermogravimetric analysis, NMR, dynamic mechanical thermal analysis, and transmission electron microscopy. By varying the polymerization time and iniferter concentration, the composition and the sequence length were controlled. The analysis confirmed the chain microphase separation in the multiblock copolymers. 

In a more simple and cheap way, silver clusters can be prepared in aqueous solutions of commercially available polyelectrolytes, such as poly(methacrylic acid) (PM A A) by photo activation using visible light [20] or UV light [29]. Ras et al. found that photoactivation with visible light results in fluorescent silver cluster solutions without any noticeable silver nanoparticle impurities, as seen in electron microscopy and from the absence of plasmon absorption bands near 400 nm (F = 5-6%). It was seen that using PMAA in its acidic form, different ratios Ag+ MAA (0.15 1-3 1) lead to different emission bands, as discussed in the next section (Fig. 12) [20]. When solutions of PMAA in its sodium form and silver salt were reduced with UV light (365 nm, 8 W), silver nanoclusters were obtained with emission band centered at 620 nm and [Pg.322]

Panyam, J., Sahoo, S.K., Prabha, S., Bargar, T., Labhasetwar, V., Fluorescence and electron microscopy probes for cellular and tissue uptake of poly(D,L-lactide-co-glycolide) nanoparticles. Int J Pharm 262, 1-11 (2003). 

Microspheres were monitored by scanning electron microscopy (SEM JEOL 35C), and their diameters were determined from the corresponding SEM microphotographs. Typically, ca. 500 particles in randomly sampled areas of microsphere specimens were analyzed. Molecular weight of poly(L-Lc) was determined by GPC. A system consisting of a LKB 2150 pump, Ultrastyragel 1,000, 500, 100, 100 columns, and Wyatt Optilab 903 interferometric refractometer was used for the measurements. GPC traces were analyzed by using calibration with narrow polydispersity < 1.15)... 

---