Novel symmetrical bis(unsymmetrical t-alkyl and t-aralkyl azo) compounds of the general formula I: r -- n = n -- r.sub.12 -- n = n -- r' (i) where R = R' = (R").sub.3 C--, e.g., 1,2-ethylene bis(4-t-butylazo-4-cyanovalerate); and the use of I for sequential generation of free radicals, e.g. styrene monomer and 1,2-ethylene bis(4-t-butylazo-4-cyanovalerate) are reacted to obtain polystyrene containing attached azo groups which in turn is reacted with methyl methacrylate monomer to obtain a block copolymer of polystyrene and poly(methyl methacrylate).
化合物I的通式为:r -- n = n -- r.sub.12 -- n = n -- r' (i),其中R = R' = (R").sub.3 C--,例如1,2-
乙烯基双(4-t-丁基偶氮基-4-
氰基酸酯)。该化合物可用于顺序自由基产生,例如,
苯乙烯单体和1,2-
乙烯基双(4-t-丁基偶氮基-4-
氰基酸酯)反应,得到含有偶氮基的聚
苯乙烯,然后再与
甲基丙烯酸甲酯单体反应,得到聚
苯乙烯和
聚甲基丙烯酸甲酯的嵌段共聚物。