CuX/bpy催化体系中甲基丙烯酸甲酯的原子转移自由基聚合

Living Radical Polymerization of MMA Promoted by EPN-Br / CuX / bpy

讨论了以α－溴代丙酸乙酯（ＥＰＮ－Ｂｒ）为引发剂、卤化亚铜（ＣｕＸ）／联二吡啶（ｂｐｙ）为催化剂，８０℃下，甲基丙烯酸甲酯（ＭＭＡ）在不同溶剂中的原子转移自由基聚合（ＡＴＲＰ）反应。通过对催化剂ＣｕＢｒ或ＣｕＣｌ及几种溶剂的考察，发现在８０℃下ＥＰＮ－Ｂｒ／ＣｕＢｒ／ｂｐｙ能有效控制丙烯酸甲酯（ＭＡ）的本体ＡＴＲＰ反应，但并不能很好地控制ＭＭＡ在ＥＡｃ溶剂中的“活性”自由基聚合。当用ＣｕＣｌ代替ＣｕＢｒ为催化剂时，ＭＭＡ在ＥＡｃ中的聚合反应为一可控聚合过程，引发效率为０．８４。通过加入过量的催化剂或选用对催化剂溶解度大的溶剂，如ＴＨＦ、乙腈，能有效地提高引发效率。在乙腈中，催化剂溶解度较大，ＥＰＮ－Ｂｒ／ＣｕＣｌ／ｂｐｙ反应体系对聚合产物（ＰＭＭＡ）的分子量和分子量分布控制良好。对该体系的聚合动力学和分子量研究表明：在乙腈中，ＥＰＮ－Ｂｒ／ＣｕＣｌ／ｂｐｙ引发ＭＭＡ的聚合反应为一“活性”自由基聚合。用离子色谱分析了ＰＭＭＡ的端基卤素、用可见光谱分析了ＣｕＣｌ／ｂｐｙ在ＥＡｃ或乙腈中的络合结构，对可能的反应催化中心进行了讨论。

The solution ATRP of MMA at 80℃initiated by EPN-Br / CuX(X=Br,Cl)/bpy was investigated in detail. The results show the reaction system of EPN-Br/CuBr/bpy (1∶1∶3) in EAc fails to control the “living” radical polymerization of MMA. However, when the CuCl/bpy was chosen as catalyst instead of CuBr/ bpy,the polymerization was controlled with lower initiating efficiency(0.84). Further investigation indicates that the initiating efficiency is increased at the reaction condition of EPN-Br/CuCl/bpy(1∶2∶4) in EAc or EPN-Br/CuBr/bpy (1∶1∶3) in solvent with higher solubility to catalyst, such as THF and acetonitrile. Moreover, the logarithmic conversion data plotted against time ( ln(/) vs time ) displayed a first order kinetics in monomer, and the molecular weight increase linearly with the conversion in the ATRP of MMA initiated by EPN-Br/CuCl/bpy(1/1/3) in acetonitrile. The possible catalyst active center ([Cu(I)L2]X ) during the polymerization was discussed through the analysis of terminated halogen during the polymerization of CuCl/bpy in organic solvents. 