POLYMERIZATION OF METHACRYLIC-ACID ESTERS WITH THE AGED SYSTEM OF LANTHANUM VERSATATE AND P-CHLOROBENZENEDIAZONIUM TETRAFLUOROBORATE

The aged system of lanthanum versatate (1) and p-chlorobenzenediazoniu m tetrafluoroborate (2) was found to initiate effectively the radical polymerization of acrylic monomers including alkyl methacrylates, buty l acrylate and acrylonitrile, although its initiating activity is lowe r than that of the non-aged system. The polymerization of methyl metha crylate (3) with the aged 1/2 system was studied kinetically in aceton e. The initial polymerization rate (R(p)) is expressed by R(p) k . [ag ed 1/2](0.80) . [3](1.1) at 50 degrees C. The overall activation energ y of the polymerization is 59.0 W mol(-1). The molecular weight of the resulting poly(3) formed in the early stage increases with increasing conversion. The polymerization system involves a persistent radical s howing a four-line EPR spectrum with a g-value of 2.004. A three-line spectrum due to the nitroxyl radical was also observed at lower monome r concentrations. The total concentration of persistent radicals was f ound to correspond well to the instantaneous polymerization rate. The copolymerization of styrene (M(1)) and 3 (M(2)) with the aged initiato r system was examined at 50 degrees C in acetone. r(1) and r(2) are 0. 19 and 0.47, respectively. The former is considerably smaller than tha t (0.52) reported for the conventional radical polymerization.