Radical stabilization of aromatic diacetylenes (dinaphthylbutadiynes) in the free radical polymerization of methyl methacrylate

In the presence of naphthylbutadiyne (DNB) and dinitronaphthylbutadiyne (DNNB), ESR signals of propagating PMMA radicals with concentration of the order of 1014–1015 radicals per ml were observed from early stage of polymerization, and their concentration increased with conversion. The concentration of the DNNB system was about double of that of the DNB system, indicating that electron accepting groups increase the stabilization of PMMA radicals. No fragment of the butadiynes are found in the PMMA obtained, indicating that the aromatic diacetylenes stabilize free radicals without suffering the addition reaction.