Staining of polymers

Staining of polymers can be conducted either before or after sectioning. The sample is cut into small blocks, about 1-3 mm across, and immersed in the stain solution or exposed to the vapor. Materials can be embedded and the blocks faced and then stained, especially when the stain diffuses into the polymer slowly. This method permits the sectioning and collection of the near surface material which is the most thoroughly stained. If sections can be cut prior to staining then they are stained either in the vapor, immersed in the solution, or placed on the surface of a stain droplet. 

Staining of polymers is an important part of sample preparation for electron microscopy as it provides the enhanced contrast required to image the structures. There are few staining techniques that work for a range of polymers and there are several stains with limited applicability. For many polymers there is no proven stain, and thus preparative treatments must be found by experimentation. This sunnnary will provide a listing (Tables 4.1-4.3) of those polymers which have been shown to be stained by the various reagents described in this section. In addition, several stains that are applicable for only a few polymers are also listed here, even though they were not fully described. 

Staining of polymers can be conducted either before or after sectioning. The sample is cut into small blocks, about 1-3 mm across, and immersed in the stain solution or exposed to the... 

Hydroxyhydroquinone and pyrogaHol can be used for lining reactors for vinyl chloride suspension polymerization to prevent formation of polymer deposits on the reactor walls (98). Hydroxyhydroquinone and certain of its derivatives are useful as auxiUary developers for silver haUde emulsions in photographic material their action is based on the dye diffusion-transfer process. The transferred picture has good contrast and stain-free highlights (99). 5-Acylhydroxyhydroquinones are useful as stabilizer components for poly(alkylene oxide)s (100). 

Some of the most difficult heterophase systems to characterize are those based on hydrocarbon polymers such as mbber-toughened polypropylene or other blends of mbbers and polyolefins. Eecause of its selectivity, RuO staining has been found to be usehil in these cases (221,222,230). Also, OsO staining of the amorphous blend components has been reported after sorption of double-bond-containing molecules such as 1,7-octadiene (231) or styrene (232). In these cases, the solvent is preferentially sorbed into the amorphous phase, and the reaction with OsO renders contrast between the phases. 

The formation and role of hydroperoxide groups, particularly in the early stages of polymer oxidation is well discussed in the introduction to the next chapter and also features in many of the references cited in this chapter. Their detection and quantification is therefore important. Although this can be done directly or implicitly through many of the instrumentation techniques discussed in this chapter, there are several tests that have been developed, some of which are still widely used, that are based more on chemical methods, titration or staining. The majority have been applied to polyolefins, especially polyethylene. 

Fig. 8.11 (A and B) Expression and purification of insulin-polymer fusion protein detected in copper (A) and Coomassie (B) stained gels. The same gel was first stained with copper, destained and restained with Coomassie R-250. Lane 1 Prestained marker Lane 2 Purified extract of polymer-insulin fusion protein from the chloroplast vector pSBL-OC-40Pris Lane 3 Reverse orientation of fusion protein from pSBL-OC-40Pris Lane 4 Purified extract of polymer-insulin fusion protein from the chloroplast vector pLD-OC-40Pris ...

Nylon blends, dyeing, 9 204 Nylon block copolymer, 19 762 Nylon carpet fibers, stain-resistant, 19 764 Nylon-clay nanocomposites, 11 313-314 Nylon extrusion, temperatures for, 19 789t Nylon feed yarns, spin-oriented, 19 752 Nylon fiber(s), 24 61 production of, 19 740 world production of, 19 7654 Nylon fiber surfaces, grafting of polymers on, 19 763-764... 

Styrolux is an example of a nanostructured polymer which is used in food packaging. It is a polystyrene-polybutadiene block copolymer where polymer chains are build up of alternating polystyrene and polybutadiene blocks. These blocks appear as dark lamellae in the TEM image due to the staining of the polybutadiene with OSO4. This structured nanoscale architecture of the pol5mier, which can be controlled during manufacture, allows the optimum combination of impact resistance and transparency. 

Recently, a method has been developed to microinject cell-polymer suspensions into 3-D collagen matrices in a 96-well plate format. This was used to perform a proof-of-principle screen of known signaling pathway inhibitors in murine breast cancer cells. The cells were visualized by staining of the actin cytoskeleton and effects of the compounds measured using multiparametric imaging. The system also proved amenable to the use of enzymatically... 

In general, it is almost impossible to incorporate selective stains into polymers in a high enough concentration to produce contrast enhancement in thin sections [2]. An exception is the use of osmium tetroxide to stain unsaturated rubbers. 

What type of polymer would be best to use in the manufacture of stain-resistant carpets ... 

As with any scientific endeavor, chance discovery played an important role in the development of polymers. In all cases, however, there was a scientist with an open and innovative mind who was ready to recognize and take advantage of a chance observation. Charles Goodyear accidentally tipped sulfur into heated natural rubber to discover vulcanized rubber. Christian Schobein inadvertently wiped up a nitric acid spill with a cotton rag to discover nitrocellulose. Jaques Brandenberger thought of cellophane as he observed the accidental stains on tablecloths. Also, as was discussed in Chapter 1, Teflon was discovered upon the unexpected disappearance of a chemical in a gas cylinder that Roy Plunkett was compelled to saw in half. 

Landells, G., and C. S. Whewell Preparation and properties of regenerated cellulose containing vinyl polymers. I. Internal deposition of polymers. J. Soc. Dyers Colourists 67, 338 (1951). II. Staining, swelling, and stiffness characteristics. J. Soc. Dyers Colorists 71, 171 (195S). III. Moisture relations. J. Soc. Dyers Colorists 73, 496 (1957). 

Figure 3. Ultrathin cross sections of OsO, -stained two-stage (S//S-B) latex particles at the stage ratio of 20/80 showing the effect of polymer compatibility ((A) 30 parts butadiene (LS-7) (B) JO parts butadiene (LS-8) and (C) 5 parts...

Figure 8. Transplanted kidney stained for C4d using (a) an ultrasensitive polymer detection system (EnVision) and (b) standard strepavidin-biotin peroxidase system. There was clear staining of peritubular capillaries in (b) compared to the polymer system where the stain extended into the intertubular interstitium masking the capillaries.

As it was demonstrated by staining the oxidized polypropylene and its observation by UV microscope, a high degree of inhomogeneity at the micron level was observed even for the most thoroughly annealed samples. In most cases this is clearly associated with the catalyst residues. An observation of microdomains in the oxidized polymer in which the degree of oxidation is by far pronounced than in the rest of polymer may be explained by the effect of higher oxidation state of transition metal ions M which interact directly with polymer ... 

It has already been pointed out that it is not only PolyPs but other anionic polymers, such as [X)I y-ft -hy< I rox ybutyrate, which may form metachromatic granules in the cells of prokaryotes. However, recently a number of methods for differential staining of PolyPs and polyhydroxyalkanoate-containing granules in cells have been developed (see the review of Serafim et al, 2002). 

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