ORGANOCUPRATES AS INITIATORS FOR THE POLYMERIZATION OF METHYL-METHACRYLATE IN THF

Several types of lithium organocuprates (I) e.g. R2CuLi, RR'CuLi, R3Cu Li2, R2CuLi2X (X= CN, SCN), were prepared and used as polymerization i nitiators for methyl methacrylate in THF at temperatures ranging from -30 to +20-degrees-C. Polymerization initiated by a mixed homocuprate, e.g. lithium n-butyl(thien-2-yl)cuprate was studied in more detail. K inetic measurements indicated an overall large (-4 to -14 kcal ) appar ent negative activation energy of polymerization in the -30 + +20-degr ees-C temperature range. The reaction was shown to haw a kinetic order of about 1.5 with respect to initiator concentration. Conductance mea surements indicate that the equivalent conductance increases with init iator concentration in the 10(-2)+10(-1) M range indicating the format ion of multiple ions formed by intermolecular association. The data ar e consistent with a polymerization involving aggregated ion pairs of a s yet undetermined composition. The negative activation energy is tent atively interpreted as due to the exothermic formation of aggregates e xisting as highly solvated im pairs.