原子转移自由基聚合制备聚(甲基丙烯酸甲酯-b-苯乙烯)时单体聚合顺序对嵌段效率的影响

采用原子转移自由基聚合研究了聚（ 甲基丙烯酸甲酯 ｂ 苯乙烯） 嵌段共聚物的合成，实验结果表明，当先进行甲基丙烯酸甲酯的聚合，然后再进行苯乙烯的聚合时，得到了完全的嵌段共聚物；反之，如果改变单体的聚合顺序，则嵌段效率很低．用聚合物末端Ｃ—Ｘ（Ｘ＝ Ｃｌ，Ｂｒ） 键的断裂能对实验结果进行了解释．

EFFECT OF MONOMER POLYMERIZATION SEQUENCE ON THE SYNTHESIS OF POLY(METHYL METHACRYLATE| b |STYRENE) BY ATOM TRANSFER RADICAL POLYMERIZATION

The synthesis of poly(styrene| b |alkyl acrylate) and poly(styrene| b |methyl methacrylate) block copolymers by atom transfer radical ppolymerization (ATRP) with CuX(X=Cl,or Br)/2,2′|bipyridine (bipy) complex as the catalyst was studied in this work. When chlorine capped polystyrene (PSt|Cl) synthesized by ATRP was used to initiate the polymeriztion of methyl acrylate, ethyl acrylate or n|butyl acrylate in the presence of CuCl/bipy, well|defined poly(styrene| b |alkyl acrylate) block copolymers were obtained. However, when PSt|Cl or PSt|Br was used as macroinitiator to initiate the polymerization of methyl methacrylate with CuCl/bipy or CuBr/bipy as the catalyst respectively,there were two peaks in the GPC chromatogram, one of which was the same as that of the macroinitiator PSt|X(X=Cl,or Br), showing the blocking efficiency was low. While the ATRP of styrene with PMMA|Cl as the macroinitiator gave well|defined poly(methyl methacrylate| b |styrene) block copolymer.These results were explained according to the difference of C|X bond dissociation energy between PSt|X and PMMA|X(X=Cl,or Br).