Effect of isotopic composition on free-radical reactions in polyolefins. [Gamma and uv radiation]

Journal Article · Thu Jan 01 04:00:00 EST 1976 · J. Polym. Sci., Polym. Chem. Ed.; (United States)

DOI:https://doi.org/10.1002/pol.1976.170140610· OSTI ID:7234497

Milinchuk, V K; Klinshpont, E R; Vasilenko, V V

On substitution of hydrogen by deuterium the radiation yield of free radicals in polyolefins decreases ca. 2-fold. Under ultraviolet illumination (lambda <300 nm) in deuterated polyethylene (DPE), allyl radicals are converted into alkyl radicals --CD/sub 2/CDCD/sub 2/-- (hfs constants ..cap alpha../sub alpha/sup D/ = 3.2 Oe, ..cap alpha../sub beta/sup D/ = 4.4 Oe); in deuterated polypropylene (DPP), allyl and peroxide radicals are converted into alkyl radicals --CD/sub 2/C(CD/sub 3/)CD/sub 2/--(..cap alpha../sub beta/sup D/ = 3.7 Oe). At 77/sup 0/K under ultraviolet light in ..gamma..-irradiated polyethylene (PE) and DPE, triene, tetraene, dienyl, trienyl, and tetraenyl radicals are formed. Deuterium subsitution has no effect on absorption spectra of polyenyl radicals and polyenes. In polyolefins the quantum yields of photochemical reactions of allyl and peroxide radicals are 0.1 to 1.0. Photochemical reactions of peroxide radicals result in a radical concentration increae of ca. 3-fold. In reactions of peroxide radicals in the dark, a kinetic isotope effect has been observed. Activation energies of substitution reactions of peroxide radicals are in PE, 9.3 +- 0.3 kcal/mole; in DPE, 10.2 +- 0.3 kcal/mole; in PP, 12.7 +- 0.4 kcal/mole; in DPP, 14 +- 0.5 kcal/mole. Possible mechanisms of the effect of polyolefin isotope composition on radical formation by high energy irradiation as well as on photochemical and dark reactions of free radicals are discussed. The effect of the energy released from phototransformations and radiationless deactivation of macroradicals on the migration of free valence is also considered.

• Research Organization: Inst. of Physical Chemistry, Moscow
• OSTI ID: 7234497
• Journal Information: J. Polym. Sci., Polym. Chem. Ed.; (United States), Journal Name: J. Polym. Sci., Polym. Chem. Ed.; (United States) Vol. 14:6; ISSN JPLCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400302 -- Organic Chemistry-- Isotope Effects-- (-1987)
400500 -- Photochemistry
400600* -- Radiation Chemistry
ALKYL RADICALS
ALLYL RADICALS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DEUTERIUM
G VALUE
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PEROXY RADICALS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
POLYMERS
POLYOLEFINS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
STABLE ISOTOPES