Benzene electron micrograph

Figures 13.4-13.7 are scanning electron micrographs of 10 -, lO" -, 10 -, and 500-A Jordi gels, respectively, produced as described earlier. Generally, 100-A polydivinyl benzene gels are not used because the porosities obtainable are very low, and hence a 67% pore volume 500-A column will actually do...

Figure 1 The transmission electron micrographs of the crosslinked products of MCI cast from benzene, (a) at a 0.05 wt% polymer concentration and shadowed with Cr at an angle of 20°, and (b) at a 0.05 wt% concentration [24].

Polyacrylonitrile is also quite insoluble in benzene, so that dilution of the monomer with benzene does not change the heterogeneous polymerization in any essential way. The effect of dilution on the specific surface is shown in Table III. There is a discernible trend toward lower surface areas at low acrylonitrile concentration. This is also evident in electron micrographs (Figure 2), where the particles from a benzene-acrylonitrile mixture are more compact and dense in appearance than those in Figure 1. Nevertheless, the surface is still extensive, and this has profound effects on the rate of polymerization. 

Figure 10. Scanning electron micrographs of membrane cross-sections prepared from a solution of 15 % polyamide in a) DMAc b) 75 % DMAc and 25 % benzene and c) 60 % DMAc and 40 % benzene by precipitation in water at room temperature.

An electron micrograph of benzene molecule, which shows clearly the ring structure. 

As we saw in Section 9.8, the properties of benzene are best represented by both of An electron micrograph of benzene... 

Figure 4-13. IVans mission electron micrograph of Pt clusters in zeolite L. [184] Virtually all the clusters are in the zeolite pores. They have an average of 5 or 6 atoms each, as determined by EXAFS spectroscopy. The material shown here is a highly selective catalyst for the conversion of n-hexane into benzene and Hj. Catalysts of this type will soon be applied industrially for this reaction. Reproduced from Catalysis Letters with permission of J. C. Baltzer AG.

Figure 3 shows a transmission electron micrograph of poly(NMMAm) in a poly(p-methylstyrene)(p-MeSt) matrix. The sample was prepared by an AIBN-initiated polymerization of a p-MeSt solution containing dispersed poly(NMMAm). Poly-(NMMAm) formed in a photo-sensitized polymerization of NMMAm with DBPO in benzene was used for this electron microscopic examination. 

Figure 12a shows an electron micrograph of the polymer particles formed in the polymerization of NMMAm (3.68 mol/1) with AIBN (1.01 x 10 mol/I) at 50 °C for 160 min in benzene. A cluster of several polymer particles of 0.8-1.8 pm diameter was observed. Such a wide size distribution of the particles su ests that an a lomera-tion of the primary particles occurred during polymerization. Furthermore, the particles had rough surfaces, implying that the propagation proceeded at isolated points on polymer surfaces. 

Lastly, the effect of the casting solvent on the domain structure of the block copolymer in the solid state was investigated. GBG-4 membrane cast from CF includes rather fine cylindrical domains (Figure 9-H), while an electron micrograph reveals more coarce domains for the same sample membrane cast from benzene (Figure 9-1). 

Fig. 25 a and b. Electron micrographs of the free surface of films casted from a benzene solution of two fractions of polyphenylisobutylsilsesquioxane with the molecular weight 100,000 a and 200,000 b >... 

It is interesting to note that some of their electron micrographs exhibit features similar to those of a linear polystyrene-block-poly((4-vinylbenzyl)di-methylamine)-block-polyisoprene triblock copolymer with almost equal amounts of the three components, when cast from benzene [168] (Fig. 16c,d). Also a quaternary star copolymer consisting of polystyrene, polyisoprene, polybutadiene, and poly(4-methylstyrene) was reported, but no morphological characterization was given [79]. 

Figure 4 Electron micrograph of a film of a polystyrene-h/oc/c-polyisoprene-h/oc/c-polystyrene (12 500 35 500 12 500 M ) copolymer cast from benzene solution (the molecular weights of the blocks are given inside the brackets). View shows polystyrene cylinders end-on in a polyisoprene matrix. Scale bar indicates 50 nm (reproduced from ref. 29 with permission of...

Figure 15 Transmission electron micrographs of microsphere SV500-M cast from benzene (a) 0.05 wt % of polymer concentration and shadowed with Cr (b) 1 wt % of polymer concentration. (From Ref 45.)...

Studies by optical microscopy of the material left after evaporating the benzene show a variety of what appear to be crystals—mainly rods, platelets and star-like flakes. Figure 1 shows a micrograph of such an assemblage. All crystals tend to exhibit six-fold symmetry. In transmitted light they appear red to brown in colour in reflected light the larger crystals have a metallic appearance whereas the platelets show interference colours. The platelets can be rather thin and are thus ideally suited for electron-diffraction studies in an electron microscope (see the inset in Fig. 3). 

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