Ether linkages, scission

Therefore, phenols must be participating directly in the course of scission of ether linkage. 

The study indicated that the random chain scission occurs primarily at the ether linkage, and only under more severe pyrolysis conditions does it involve the ketone linkage. 

The photodegradation is assumed to be initiated either by hydroperoxides initially present or by scission of the ether linkage [122]. 

The radiolysis of either a complex carbohydrate, such as starch, or solutions of simpler saccharides, such as glucose or sucrose, leads primarily to scission of C-H bonds and disruption of the ether linkages between glucose units [32-34]. 

Numerous ways to evaluate the degradation behaviour of polyarylene sulfones are reported in the literature. Danilina and co-workers [17] used infrared (IR) analysis for the pyrolysates of PES and PSF along with a change in the absorption peaks after two hours at 470 °C, they showed the formation of sulfur dioxide and phenol from the scission of sulfone and ether linkages. Crossland and co-workers [18] reported the results of TGA and Py-MS in the evaluation of the pyrolysis mechanism and pyrolysates of various PSF main-chain scission and hydrogen abstraction were indicated. However, the relative stability of the different PSF could not be postulated... 

The thermotropic polymers used in these studies are all random copolyesters. As has previously been documented for other types of polymers, the presence of aromatic rings and/or conjugated bonds, and the absence of CH2—CH2 and ether linkages yield materials most resistant to beam damage (by processes such as chain scission and cross-linking). The family of thermotropic copolyesters most extensively studied here comprises the following randomly sequenced segments ... 

Reacting polyepichlorohydrin with sulfite introduces sulfonic acid sites, but some chain scission occurs at ether linkages, depending on the nature of the crosslinker used (9). Cleavage is more... 

Although polymers in-service are required to be resistant toward hydrolysis and solar degradation, for polymer deformulation purposes hydrolysis is an asset. Highly crystalline materials such as compounded polyamides are difficult to extract. For such materials hydrolysis or other forms of chemolysis render additives accessible for analysis. Polymers, which may profitably be depolymerised into their monomers by hydrolysis include PET, PBT, PC, PU, PES, POM, PA and others. Hydrolysis occurs when moisture causes chain scissions to occur within the molecule. In polyesters, chain scissions take place at the ester linkages (R-CO-O-R ), which causes a reduction in molecular weight as well as in mechanical properties. Polyesters show their susceptibility to hydrolysis with dramatic shifts in molecular weight distribution. Apart from access to the additives fraction, hydrolysis also facilitates molecular characterisation of the polymer. In this context, it is noticed that condensation polymers (polyesters, -amides, -ethers, -carbonates, -urethanes) have also been studied much... 

In disaccharides and polymeric carbohydrates, the ether-type radicals such as 7 and 8 have the radical site proximate to the glycosidic linkage and therefore play a major role in its scission (see below). In glucosamine [20] and N-acetylglucosamine [21] as well as in their related polymers chitin, chitosan and hyaluronic acid, one must further consider radicals of the type 9-11. Thus, one may expect that in addition to the behaviour shown by the prototypical carbohydrate radicals, reactions such as are observed with amino acids (c/. [22]) and peptides (c/. [23-25]), may also play a role. 

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