Hydroperoxide groups poly

Depending on the nature of the sulfur or phosphorus compound used, the product R2S = O or R3P = O may undergo a number of further reactions with ROOH groups, all of which convert the hydroperoxide group into an alcohol. These compounds tend to be only weakly effective so are generally used in conjunction with synergistic promoters. Suitable mixtures are used to stabilise a variety of polymers including poly(alkenes), ABS, and poly(stryrene). 

In the field of free radicals and liver injury there is a vast body of work concerning a group of compounds that have proven to be of great value as experimental models but are of little clinical significance. The most frequently used compounds are quinones (particularly menadione), paraquat and diquat, bromobenzene, and organic hydroperoxides, particularly cumene hydroperoxide and r-butyl hydroperoxide (see Poli et al., 1989b). 

Breck at al (68) havs recently examined the reactivities of a number of saturated and unsaturated polymers towards singlet oxygen generated by microwave generator. The saturated ohain polymers as polystyrene,polyurethane and polyethylene were found to be inert within the experimental conditions with singlet oxygen,while the unsaturated polymers as poly-dienes were found to react quite readily.In this paper concentration of hydroperoxide groups has been measured. 

Sensitization of degradation has been achieved by copolymerizing acenaphthylene, and chloromethyl vinyl ketone. The mode of action of benzo-phenone has been attributed to its ability to sensitive decomposition of hydroperoxide groups. Blends of polystyrene with poly(phenylene oxide) have attracted some attention. " It is worth noting that the last paper reports that singlet oxygen had no effect on pure polystyrene or its blends. ... 

Olefinic unsaturation, carbonyl and hydroperoxide groups are also incorporated into the poly(vinyl chloride) molecule during the mechanodegra-dation process. 

The initial rates of both thermal and photo-oxidative degradations are linearly related to the concentration of hydroperoxide groups in poly(vinyl chloride) samples, but not to the unsaturated groups and carbonyl concentration. 

Allen, N. S., Edge, M., Mohammadian, M. and Jones, K., UV and thermal hydrolytic degradation of poly (ethylene terephthalate) importance of hydroperoxides and benzophenone end groups, Polym. Degrad. Stabil., 41, 191-196 (1993). 

One of the first attempts to extend polymer-assisted epoxidations to asymmetric variants were disclosed by Sherrington et al. The group employed chiral poly(tartrate ester) hgands in Sharpless epoxidations utilizing Ti(OiPr)4 and tBuOOH. However, yields and degree of stereoselection were only moderate [76]. In contrast to most concepts, Pu and coworkers applied chiral polymers, namely polymeric binaphthyl zinc to effect the asymmetric epoxidation of a,/9-unsaturated ketones in the presence of terPbutyl hydroperoxide (Scheme 4.11). 

The utility of classical antioxidants such as hindered amines, phenols, and nitrones for the stabilization of pristine polyacetylene (29), poly(methyl acetylene) (30), and poly(l,6-heptadiyne) (31) has been examined. Poly(methyl acetylene), although dopable to only low conductivities (10" S/cm), has similar oxidative behavior to polyacetylene and serves as a good model for other polyenes. In general, the improvement in stability of poly(methyl acetylene) was limited, but combinations of hindered phenols and hydroperoxide scavengers resulted in a factor of 5 decrease in the oxidation rate (30) as monitored by the appearance of IR absorption bands attributable to carbonyl groups. These degradation rates are still too high for the use of these polyenes in an unprotected environment. The compatibility of such stabilizers with the dopants commonly used for polyacetylene was not studied. 

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