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

Several types of lithium organocuprates (I) e.g. R2CuLi, RR'CuLi, R3CuLi2, R2CuLi2X (X= CN, SCN), were prepared and used as polymerization initiators 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. Kinetic measurements indicated an overall large (-4 to -14 kcal ) apparent negative activation energy of polymerization in the -30 + +20-degrees-C temperature range. The reaction was shown to haw a kinetic order of about 1.5 with respect to initiator concentration. Conductance measurements indicate that the equivalent conductance increases with initiator concentration in the 10(-2)+10(-1) M range indicating the formation of multiple ions formed by intermolecular association. The data are consistent with a polymerization involving aggregated ion pairs of as yet undetermined composition. The negative activation energy is tentatively interpreted as due to the exothermic formation of aggregates existing as highly solvated im pairs.