Studies On The Applications Of Rare Earth Catalyst In Ionic Liquids And Reverse ATRP

The applications of rare earth catalysts in ionic liquids and reverse atom transfer radical polymerization (reverse ATRP) were studied in this dissertation.Rare earth catalyst-neodymium versatate (Nd(VA)3)/Al(/-Bu)3 was employed to catalyze the polymerization of methyl methacrylate (MMA) for the first time. Effects of different conditions on the polymerization were studied systemically. Results show that the polymerization of MMA by rare earth catalyst in ionic liquids could be conducted successfully. Furthermore, the rate of polymerization and the molecular weight of the polymer obtained in ionic liquids were much higher than that in toluene or in bulk at the same conditions. It can be concluded that ionic liquids can accelerate the polymerization of MMA. Moreover, it was found that the aging of catalysts disadvantages the polymerization, while benefits to the polymerization in toluene. When [MMA]=3.0mol/L and [MMA]/[Nd]=300, the highest conversion and molecular weight can be achieved in [emim]BF₄ at 60℃. IR, GPC, DSC and ¹H-NMR were used to characterize the structure and property of PMMA obtained in ionic liquid.The polymerization of styrene by ternary catalytic system, Nd(VA)3/Al(/-Bu)3/ CCl₄, were carried out in ionic liquids. Results show that St can't be polymerized in toluene by the ternary catalytic system but no polymerization with no III additive in the system. However, the conversion of monomer was 37% in ionic liquids with no III additive. However, the conversion of monomer was 37% in ionic liquids at the same conditions. The aging of catalysts can increase the molecular weight of PSt obtained in ionic liquids, while didn't increase the conversion of monomer. And the optimum reaction conditions are as follows: [St]=3.8molL^-1 [St]/[Nd]=300, Al/Nd=27, CCl₄/Nd=7 (molar ratio), 60°C, 24h, in [emim]BF₄. Under these conditions, PSt with M_n of 5.13 ×10⁴ and M_w/M_n of 3.52 could be prepared. PSt obtained in ionic liquid was characterized by means of IR, GPC, DSC and ¹H-NMR.The kinetic studies indicated that St polymerization in ionic liquids is first orderwith respect to the monomer concentration and catalyst concentration, Respectively. The apparent propagating constant (kp) is O.lmol^min"1 at 60"C, And the apparent activation energy (Ea) amounts to 67.5kJmol"1.Copolymerization of MMA with St was also conducted in ionic liquids by the same ternary catalytic system. It was found that random and block copolymers can be prepared in ionic liquids by different feed sequences. However, only homopolymer could be obtained when MMA was polymerized first in ionic liquids. Effects of different reaction conditions on the polymerization were studied systemically. IR, GPC, DSC, 2H-NMR and 13C-NMR were used to characterize the structure and property of the copolymers of MMA and St.Ionic liquids-supported rare earth catalysts were synthesized for the first time, and it was used in the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Studies show that La system presented the highest activity among the rare earth elements investigated, and the optimum reaction conditions are as follows: [DTC]=2.5molL"x, [DTC]/[La]=200, 60 °C ,0.5h. PDTC with monomer conversion of 88.6% and Mn of 2.58xlO4 could be prepared under the above conditions. IR, GPC, *H-NMR and DSC were used to characterize PDTC. Through analyzing the end group in PDTC terminated by isopropanol, it can be concluded that the polymerization of DTC by ILs-supported rare earth catalyst was via the breaking of acyl-oxygen bond, which is accord with the polymerization by single component catalyst of rare earth.The copolymerization of CL and DTC by ILs-supported rare earth catalyst was also conducted. Results indicate that both random and block copolymer of CL and DTC can be obtained by different feed sequences. Effects of different rare earths, temperature, solvents, monomer concentration, time and molar ratio of monomer/catalyst were investigated. The characterizations by IR, GPC, DSC, *H-NMR and 13C-NMR testified the formation of PCL-co-PDTC and PCL-b-PDTC copolymers.Ring-opening polymerization of e -caprolactone in ionic liquid was carried out with LnCl;$/epoxide as catalyst. The results show that LnCb/epoxide could catalyzethe polymerization of CL in ionic liquid effectively. The effects of different rare earth chlorides, epoxides, monomer concentration, the molar ratio of epoxide/LnClj and CI/LnCb, polymerization temperature and time on the polymerization of CL were investigated. When the ratio of PO/ ErCl3 is 30, PCL with a viscosity molecular weight of 2.54 X104 and the conversion of 96.0% can be prepared at 60 °C in 30 min. Moreover, the activities of GdCb and ErCb were higher than other rare earth chlorides investigated. The structure and thermal properties of PCL were characterized by means of ^-NMR and DSC respectively. The analyses of PCL structure showed that the polymerization of CL proceeds according to 'coordination-insertion' mechanism with s with acyl-oxygen bond cleavage of the monomer.Reverse ATRP of methyl methacrylate mediated by AIBN/SmCla/lactic acid system was investigated for the first time. The one electron transfer reaction of SmCl3 to SmCl2 was employed in the living radical polymerization successfully. The kinetics studies indicated that the polymerization is first order to monomer concentration. Moreover, the number average molecular weight increased linearly with the monomer conversion, Mn, gpc are close to the theory molecular weight and Mw/Mn were narrower (less than 1.5). These show that the polymerization of MMA was a living/controlled one in the above system. Effects of different reaction conditions, such as solvents, temperature and molar ratio of [I]o/[SmCl3]o/[bpy]o, on the polymerization have been studied. PMMA with narrower molecular weight distribution have been obtained in DMF at 80 °C. Furthermore, the apparent activation energy was calculated about 17.7kcal/mol for the reverse ATRP of MMA initiated by AIBN/SmCl3/lactic acid system.