ISSN:
0360-6376
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
α-Methylstyrene (α-Me-St) in bulk undergoes a variety of thermally induced processes which we investigated in detail by product-distribution analysis. The oligomeric products, shown by GC-MS coupling techniques and independent syntheses, consisted of nine dimers and nine trimers with no detectable higher oligomers or polymers. Two isomeric cyclobutanes and one of the open-chain unsaturated dimers were formed by a conventional two-step cycloaddition; a Flory-type diradical was the common intermediate. In contrast to these 2π + 2π products, the majority of the remaining oligomers could not be interpreted on the basis of π-electron interaction between closed shell molecules. Their structures, however, were compatible with a free radical process in which cumyl(MH·) and 1,4-dimethyl-1-phenyl-tetrahydronaphthalene-yl(THN·), which are consecutive products of 4π + 2π and 2π + 2π interactions, respectively, were involved in addition and transfer reactions. Because of the small rate of initiation and the obvious lack of free radical recombination products, a mechanism was suggested in which MH· and THN· radicals react predominantly in a closed sequence of elementary processes and to a rather small extent only by bimolecular free radical termination. Two sorts of stabilization steps, hydrogen transfer to monomer (RnH· + M → Rn + MH·) and hydrogen abstraction from a hypothetical 4π + 2π intermediate I (RnH· + I → RnH2 + THN·), are attributed to the high rates of unsaturated and saturated oligomer formation.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1982.170201020
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