92301-02-5Relevant academic research and scientific papers
Thermal Degradation of Polymers and Polymer Models. V A Model for Copoly(styrenemethyl methacrylate)
Fallon, Gary D.,Holland, Kelvyn A.,Rae, Ian D.
, p. 521 - 533 (2007/10/02)
The synthesis of (+/-)- and meso-dimethyl 2,3-dimethyl-2,3-bis(2'-methyl-2'-phenylpropyl)butanedioate from methyl 2,4-dimethyl-4-phenylpentanoate, via a silyl enol acetal, is described.The X-ray structure of the meso isomer shows serious distortions from normal bond lengths and angles, most notably a length of 162.7(4) pm for the crowded central C-C bond.The compounds were synthesized as models for head-to-head units which might form by chain termination through dimerization of macroradicals during copolymerization of styrene and methyl methacrylate.Thermal degradation of the diphenyl-substituted diesters at 210 deg gave products which may have formed by plausible routes from radicals resulting from homolytic cleavage of the crowded C-C bond.Inclusion of the phenyl groups makes the molecules more crowded than the corresponding tetraesters which were reported earlier, and a comparative rate study shows that the aromatic compounds are less stable to heat as a result of the penultimate effects of greater crowding at carbons which are β to the thermally vulnerable bond.
