Polymerization Of Methyl Methacrylate Catalyzed By I₂/AIBN System And By LnNa₈(O^tBu)₁₀(OH)

The thesis consists of two parts: degenerative transfer polymerization of methyl methacrylate (MMA) in the presence of iodine using AIBN as an initiator and coordination polymerization of MMA catalyzed by LnNa8(OBut)10(OH) as a single compound catalyst.Kinedics of degenerative transfer radical polymerization (DT) of MMA using AIBN / I2 system at varrous polymerization temperature was studied. The linear plots of Ln [M0] / [M] vs time indicated that polymerizations were nearly first-order with respect to monomer concentration and the concentration of active species remained almost constant. It was found that induction period was shortened obviously and polymerization rate was increased, while the molecular weight distribution (Mw / Mn) of the resulting polymers kept narrow (in the range of 1.3 to1.5) when the temperature increased from 70 0C to 90 0C. The influence of the concentration of iodine on the polymerization of MMA were investigated at the same time. Increasing the concentration of iodine used, resulted in elongater induction period, slower polymerization rate and narrower molecular weight distribution (Mw / Mn). The theoretical molecular weight (Mn, theo) of polymer depends on the concentration of iodine used. The meansured number average molecular weight of the polymers was greater than theoretical one when polymerization temperature was range from 70 0C to 80 0C,while smaller than that at 90 0C. The poly (methyl methacrylate) obtained at 70, 80 and 90 0C respectively were characterized in detail by 1H NMR. A new peak was appearred at 1.655 ppm, which was assigned as methylene group. The reasonable explanation for the appearance of new peak was that the iodo-termined of polymer Pn?I decomposed to active species which initiated the intramolecular radical rearrangement. The appearance of the methylene indicated the polymerisation at 90 0C proceeded by degenerative transfer and iniferter mechanism simultaneously.Reaction of NaOtBu with LnCl3 in 10 : 1 molar ratio in the presence of one equiv of NaOH gave LnNa8(OtBu)10(OH) (Ln = Pr (1), Sm (2), Eu (3), Er (4), Nd (5), Yb (6)) which were fully characterized and single-crystal X-ray analysis for 1?3 and 5. X?ray structure analyses revealed that the lanthanide atom is six?coordinated with five oxygen atoms of ?OtBu ligands and one oxygen atom of–OH in a distorted octahedron.All clusters can catalyze polymerization of MMA as a single compound catalyst to give iso-rich polymers. The catalytic activity depended on lanthanide metals: Nd > Sm > Eu≈Pr > Yb > Er. The homometallic complex of Na11(OBut)10(OH) and Ln3(OBut)9·2THF as well as the mixfure systems of LnCl3,NaOBut and NaOH showed no activity at all under the same reaction conditions. The results indicated that the activity showed by heterometallic alkoxide clusters may come from cooperation of lanthanide and sodium metals in cluster.