Research On The Initiator And The Ligand For Atom Transfer Radical Polymerization

The mechanism and the characterizing of "living"/controlled radical polymerization, and the mainly discussed initiator and ligand were reviewed.Investigation on N-chlorosuccinimide (NCS) initiated atom transfer radical polymerization (ATRP) of MMA as initiator and iniferter polymerization as iniferter was carried out. The solubility of complexes of nine different ligands with Cu(I) and Cu(II) in methyl methacrylate respectively, and the relationship of ATRP with the solubility was also detailed studied.1,Atom transfer radical polymerization of methyl methacrylate (MMA) has been carried out with N-chlorosuccinimide (NCS) as the initiator, and CuCl/2,2'-bipyridyl (bpy) used as the catalyst. The polymerization mechanism belonged to atom transfer radical polymerization process, which the rate of polymerization followed the first-order kinetics with respect to the decrease of monomer concentration. The polydistributions of the yield polymers were quite narrow (1.28w/M_n<1.36). But when the polymerization was run in anisole there was appeared bimodal peak in the GPC curves of the yield polymers, which indicated the system exist two polymerization mechanisms, one was ATRP mechanism, and the other one was iniferter polymerization. To develop the rate of polymerization, the other two reaction systems, NCS/CuCl/MA₅-DETA/MMA and NCS/CuCl/PMDETA/ MMA, were also introduced. The polymerization mechanism of the two belonged to the first-order kinetics. And in the first system the polydistributions of the yield polymers were quite narrow (1.19w/M_n<1.44), but in the latter one with the decreasing of monomer concentration the polydistributions were up to 1.72 over 1.5. The end-group analysis of PMMA also indicated the polymerization was initiated by the succinimidyl radicals formed from the redox reaction of NCS. Besides, the polymerization of MMA with NCS as the iniferter was also dicussed. The results showed that the main usage of NCS was transfer and termination the reaction. All of these results revealed that NCS was an special initiatorand can be used as either the initiator of ATRP or the iniferter.2, One to five substituted methacrylate diethylenetriamine (MAn-DETA, n=l-5) has been synthesized from diethylenetriamine (DETA) and methacrylate (MA) in related molar ratio. At the same time selected other four ligands, DETA, N,N,N',N',N"- penta methyldiethylenetriamine (PMDETA), dipyridine (bpy) and triethylamine (TEA) totally nine ligands as a research system to discuss the relationship of the copper-based complexes solubility with atom transfer radical polymerization. The results showed that the system without ligand, the polymerization wouldn't happen; the solubility for the copper-based complex, CuCl/MAn-DETA, n=0-5, had an important effect to the distributions of the PMMA, the more soluble copper-based complex, the narrower distributions. But the solubility of the complex did not have important effect on the polymerization rate. What considered by Matyjaszewski et al. as the homogeneous ligand, PMDETA, behaved in fact same as the heterogeneous ligand of bpy.