Re linked

NBu4]5[ AgRe7C(CO)21 2(/r-Br)] IR Yes Two Re6 octahedra, each with an interstitial C atom and two opposite faces capped by Ag and Re, linked together by sharing a common Br atom bonded to both Ag atoms 118... 

A hyperbranched polymer 47 containing Re(bipyridine)(CO)3Cl chromophores (the Re(CO)3Cl+ moiety is denoted as [Re]) linked by bipyridineethylene bridges was deposited with a sulfonated polythiophene to yield a solar energy conversion material. This displayed open-circuit voltages of 1.2 V and photocurrents of 27 iA cm 2 under solar illumination [94]. 

A re-linking process in which the broken chain ends are joined together via the antiozonant. 

Objections to the protective film theory are less clear cut. Murray (1972) has stated that if the film were to be composed only of antiozonant or ozonized antiozonant, then some rather unrealistic rates of diffusion would have to be assumed in order to form such a film in the time period observed . On the other hand the results of Andries et al (1975), who studied the surface of ozonized natural rubber compounds by attenuated total reflectance spectroscopy obtained results consistent with this theory (and for that matter the scavenger theory) but not with the re-linking and diversionary theories. 

As with all thermoplastic elastomers, the copolyesterethers can be processed as thermoplastics. They are linear polymers and contain no chemical cross-links, thus the vulcanisation step needed for thermosetting elastomers is eliminated and scrap elastomer can be re-used in the same process as virgin material (176—180). 

KD Ball, RS Beii y, RE Kunz, E-Y Li, A Proykova, DJ Wales. Erom topographies to dynamics of multidimensional potential energy surfaces of atomic clusters. Science 271 963-966, 1996. RS Berry, N Elmaci, JP Rose, B Vekhter. Linking topography of its potential surface with the dynamics of folding of a protein model. Proc Natl Acad Sci USA 94 9520-9524, 1997. Z Guo, D Thii-umalai. J Mol Biol 263 323-343, 1996. 

The mode of action of plasticizers can be explained using the Gel theory [35 ]. According to this theory, the deformation resistance of amorphous polymers can be ascribed to the cross-links between active centres which are continuously formed and destroyed. The cross-links are constituted by micro-aggregates or crystallites of small size. When a plasticizer is added, its molecules also participate in the breaking down and re-forming of these cross-links. As a consequence, a proportion of the active centres of the polymer are solvated and do not become available for polymer-to-polymer links, the polymer structure being correspondingly loosened. 

FIGURE 5.18 Methods for cleavage of disulfide bonds in proteins, (a) Oxidative cleavage by reaction with performic acid, (b) Reductive cleavage with snlfliydryl compounds. Disulfide bridges can be broken by reduction of the S—S link with snlfliydryl agents such as 2-mercaptoethanol or dithiothreitol. Because reaction between the newly reduced —SH groups to re-establish disulfide bonds is a likelihood, S—S reduction must be followed by —SH modification (1) alkylation with iodoac-etate (ICH,COOH) or (2) modification with 3-bromopropylamine (Br— (CH,)3—NH,). 

Nevertheless, the system, composed of chain fragments of oxyfluoroniobate complexes, is thermodynamically less stable. Dipole properties of fragments of a certain length are re-orientated so as to be linked into typical infinite chains. There is no doubt that the fragment re-orientation and linking process initiates the partial reduction of niobium to Nb4+ and the oxidation of fluoride to elementary fluorine. The process scheme can be presented as follows ... 

In a very recent study, it has been demonstrated116 that zinc 5,15-bis(3,5-di-tert-butylphenyl)-porphyrin (13) without any activating halogen atoms at the chromophore can be directly linked in a very simple oxidative coupling reaction with silver(I) hexafluorophosphate to a mixture of porphyrin dimers, trimers and tetramers. The separation of the product mixture was achieved by gel-permeation chromatography based on the molecular weights of the oligomers. The dimer when re-exposed to the same reaction conditions yielded 25% of the tetramer.116... 

Bellisario, R., and Cormier, M. J. (1971). Peroxide-linked bioluminescence catalyzed by a copper-containing, non-heme luciferase isolated from a bioluminescent earthworm. Biochem. Biophys. Res. Commun. 43 800-805. 

Vulcanization A process in which rubber or TS plastic (elastomer) undergoes a change in its chemical structure brought about by the irreversible process of reacting the materials with sulfur and/or other suitable agents. These cross-linking action results in property changes such as decreased plastic flow, re-... 

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