Singlet-oxygenated polymers

Table I. Activation Energies for Chemiluminescence from Autoxidized ° and Singlet-Oxygenated Polymers...

Hindered amines, such as 4-(2,2,6,6-tetramethylpiperidinyl) decanedioate, serve as radical scavengers and will protect thin Aims under conditions in which ultraviolet absorbers are ineffective. Metal salts of nickel, such as dibutyldithiocarbamate, are used in polyolefins to quench singlet oxygen or elecbonically excited states of other species in the polymer. Zinc salts function as peroxide decomposers. 

B. Ranby and J. F. Rabek (eds.) Singlet Oxygen Reactions with Organic Compounds and Polymers, Wiley, Chichester, 1978, 331 pp. 

The PP sample exposed to ozone shows for a rapid formation of polymer peroxy radicals. A singlet unsymmetric line ESR spectrum (Fig.l) is very characteristic for oxygenated polymer radicals (29). 

Emission from dimols of singlet oxygen may be detected by photomultipliers used for measurement of chemiluminescence from hydrocarbon polymers with a maximum spectral sensitivity at 460 nm. The above scheme, however, requires the presence of at least one molecule of hydrogen peroxide in close vicinity to the two recombining peroxyl radicals and assumes a large heterogeneity of the oxidation process. 

Other speculative mechanisms [26] may be proposed based on the presence of singlet oxygen and C = C in oxidized polymer. The reaction of the latter may lead to the transient formation of dioxetanes, the decomposition of which has an even higher quantum yield of luminescence than CIEEL mechanism [27],... 

In other cases fullerene antibacterial action takes place after photoirradiation of fulleropyrrolidinium salts. It is not yet clear if the photodynamic action implies the participation of superoxide and hydroxyl radicals (type I mechanism) or singlet oxygen (type II mechanism) but the efficacy is really interesting with the death of more than 99.9% of bacterial and fungal cells and a special selectivity for microbes over mammalian cells (Tegos et al., 2005). Also a sulfobutyl fullerene derivative is able to inhibit environmental bacteria after photoirradiation and it exerts its action on E. coli even if incorporated in coated polymer (Yu et al., 2005). 

In the present work, we performed the hydroperoxidation of unsaturated polymers as EPDM or polyoctenamer by using singlet oxygen photo-generated at 365 nm by anthracene / O2. The resulting hydroperoxidized polymer (POOH) was then decomposed by UV irradiation (X > 300 nm) in the presence of unsaturated monomers or nitroxyl radicals. The efficiency of these new grafted polymers as new photo- and thermo-stabilizers will be finally demonstrated. 

Copolymers of ethylene (E) or propylene (P) with acrylic acid (AA) or methacrylic acid (MA) were obtained from SP2 (USA) and used as received (EAA, PAA, PEAA, PMA). Copolymers of ethylene and vinyl alcohol (EVOH) were prepared by hydrolysis (NaOH 0,5M in methanol, reflux, 48 h), of commercial ethylene-vinyl acetate copolymers (EVA, Elf-Atochem) containing 5, 9, 14, and 18 w% of acetate. Hydroperoxides of EPDM based on 5-ethylidene-2-norbornene (0.7 mol Kg 1, Exxon) and polyoctenamer (Vestenamer, VEST, Hiils) resulted from a reaction of polymer films with singlet oxygen. 

We studied dienic elastomer films (EPDM, poly-octenamer, poly-isobutylene-co -iso-prene) which react with singlet oxygen, 02, according a "ene" reaction described elsewhere1 12. The resulting hydroperoxidized polymers can also be treated by nitric oxide and acetyl chloride but the reactions result now in the formation of nitrate and perester respectively ... 

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