异丙醇铝改进的原子转移自由基聚合催化体系

A CATALYTIC SYSTEM INCLUDING Al(OiPr)\-3 AS A PROMOTER FOR ATOM TRANSFER RADICAL POLYMERIZATION

以α溴代异丁酸乙酯［２（ＥｉＢ）Ｂｒ］ 为引发剂，溴化亚铜（ＣｕＢｒ）／ 联二吡啶（ｂｐｙ）／ 异丙醇铝［Ａｌ（ＯｉＰｒ）３］ 为复合催化剂，在环己酮溶液中进行了甲基丙烯酸正丁酯（ＢＭＡ） 的原子转移自由基聚合（ＡＴＲＰ） ．研究了异丙醇铝对聚合速率及产物分子量分布的影响．异丙醇铝可与引发剂和聚合物中的羰基配位，使相邻的Ｃ—Ｂｒ 键活化，ＡＴＲＰ 反应可以在较低温度下进行．适量溴化铜的加入，可调节ＡＴＲＰ 活性，可得到分子量可控且分子量分布窄的ＰＢＭＡ（ ＭＷＤ＝ １－３ ～１－５） ．

Atom transfer radical polymerization (ATRP) of n \|butyl methacrylates (BMA) has been achieved with ethyl 2\|bromoisobutyrate \[(CH\-3)\-2CBrCO\-2C\-2H\-5\] as an initiator and CuBr,2,2′ bipyridine(bpy) and aluminum triisopropoxide \[Al(OiPr)\-3\] as a ternary catalyst system in cyclohexanone.The kinetics and mechanism of polymerization were discussed in detail.Al(OiPr)\-3,a bulky Lewis acid,which is used as a catalytic promoter,may coordinate the ester carbonyl of the initiator and polymer and activate the carbon\|bromine bond.Therefore,BMA can be polymerized at a lower temperature.The influence of Al(OiPr)\-3 on polymerization rate and molecular weight distributions were also studied.The polymerization of BMA became slower and more controlled with CuBr\-2 than without CuBr\-2.In the absence of CuBr\-2,the polymerization of BMA were the rapider and less controlled at 28℃.In the presence of CuBr\-2,the polymers produced at 52℃ had narrow molecular weight distributions (MWD=1.2～1.5) and designed molecular weights which were nearly proportional to monomer conversion.The logarithmic conversion data plotted against time (ln(\\-0/\) versus time) followed a current first order kinetics.