以零价铜为催化剂的“活性”/可控自由基聚合反应

‘Living’/controlled Radical Polymerization by Using Zero valent Copper as Catalysts

研究了零价铜为催化剂、以 Ｃ Ｃｌ４ 为引发剂，在 ２，２′邻二吡啶（ｂｐｙ）或 １，１０邻二氮菲（ｐｈｅｎ）存在下的苯乙烯或甲基丙烯酸甲酯的“活性”／可控自由基聚合反应。研究结果表明：聚合过程中 ｌｎ（［ Ｍ ］０／［ Ｍ ］）与反应时间成线性增长关系，同时生成的聚合物的数均分子量与单体转化率也成线性增长关系，聚合过程呈现“活性”特征。

The ‘living’/controlled radical polymerization of St or MMA has been achieved by using copper powder, organic halides and some bidentate ligands. In Cu 0/phen/CCl 4/MMA/ p xylene system ( w Cu =7×10 -5 ), the “living” nature was demonstrated by the linear relationship between the MMA conversion and the number average molecular weight ( M n) of the produced poly (methyl methacrylate) (PMMA) as well as the reaction time and ln ( [M] 0/ [M] ). The molecular weight distribution (MWD) of the PMMA obtained in this case decreases from 1.80 to 1.32 during the polymerization process. The “living” nature is exhibited in Cu 0/phen/CCl 4/St system ( w Cu =4×10 -5 ), but the MWD of polystyrene was found to be quite broad (>2.0). Furthermore, it was found that in both Cu 0/bpy/CCl 4/MMA/ p xylene and Cu 0/phen/CCl 4/MMA/ p xylene system, the “living” nature was also demonstrated, although the MWD of PMMA in the former case was narrower than that in the latter case. In Cu 0/bpy/CCl 4/MMA system, the polymerizations rate decreases and the MWD of PMMA increases with decreasing the amount of Cu 0. However, the Mn of PMMA in this system is still close to the calculated one by assuming that one molecule of CCl 4 initiates only one polymer chain, indicating that CCl 4 should act as an initiator while Cu 0 acts as a catalyst. The analysis of 1H NMR spectrum of PMMA synthesized in the Cu 0/bpy/CCl 4/MMA/ p xylene system shows that CCl 4 acts as a bifunctional initiator.