The EPR spectrum of δ-irradiated polymethyl methacrylate specifically deuterated in the methylene group

Journal Article · Mon Jan 01 04:00:00 EST 1962 · Tetrahedron Letters

DOI:https://doi.org/10.1016/S0040-4039(00)70956-7· OSTI ID:4642313

Kouřím, P.; Vacek, K.

Polymethyl methacrylate (PMMA) on exposure to ionizing nadiations gives an EPR spectrum identical to the one obtained on polymerizing methyl methacrylate MMA) and trapping free radicals in the polymer gel. To clarify the nonequivalence of interaction of protons with the unpaired electron in the free radical concerned, MMA was synthesized, specifically deuterated in the methylene group. The infrared spectra of normal and deuterated MMA show the specificity and the practically quantitative degree of deuteration. The absorption band at 3010 cm/sup -1/, assigned to the stretching vibration C-- H of = CH/sub 2/ group, and other bands due to deformation vibrations C-- H of the same group in the regions 1410, 680, and 800 cm/sup -1/, disappear in the spectrum of deuterated MMA and a new band due to C-- D stretching vibration appears at 2230 cm/sup -1/. Absorption bands of stretching and deformation vibrations C-- H of --CH/sub 3/ groups remain unchanged. The monomer thus obtained was block polymerized at 60 deg C during 400 min with dibenzoyl peroxide as initiator (36 mmole/l) and then gamma irradiated with a dose of 2.64 x 10/sup 18/ ev/ml at a rate of 11.7 x 10/ sup 16/ ev/min/ml by a Co/sup 60/ source. The EPR spectra of normal and deuterated PMMA, polymerized and irradiated at identical conditions, show unequivocally the interaction equivalence of the methyl protons, that gives evidence of the correctness of the Ingram hypothesis of free rotation of the methyl group around the C-- C bond with a frequency higher than 10/sup 7/ rev/sec. The interaction with one deuteron broadens the spectral lines; the broadening at max slope amounts to 4 plus or minus 2 gauss. The quartet in the EPR spectrum of normal PMMA arises from the interaction with the methyl protons only. Should this quartet originate from an interaction with two protons of the methyl group and one proton of the methylene group, there would have to be a weaker triplet superimposed upon the quartet in the EPR spectrum of deuterated PMMA; this is, however, not the case. Therefore, the quartet of normal PMMA probably arises in such a conformation of the macroradical where the axis of the unpaired electron orbital just halves the angle between the methylene C-- H bonds. (BBB)

• Research Organization: Nuclear Research Inst., Czechoslovak Academy of Sciences, Prague
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-035913
• OSTI ID: 4642313
• Journal Information: Tetrahedron Letters, Journal Name: Tetrahedron Letters Journal Issue: 23 Vol. 3; ISSN 0040-4039
• Publisher: Elsevier
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
BENZOIC ACID
CHEMISTRY
CONFIGURATION
DEUTERIUM COMPOUNDS
ELECTRONS
FREE RADICALS
FREQUENCY
GAMMA RADIATION
INFRARED RADIATION
INTERACTIONS
IONIZATION
MAGNETIC RESONANCE
METHACRYLIC ACID
METHYL RADICALS
OXIDES
POLYMERIZATION
POLYMERS
PROTONS
RADIATION DOSES
RADIATION EFFECTS
SPECTRA
VIBRATIONS