双金属氰化物络合物催化环氧烷烃开环聚合的特征

合成了Co Zn双金属氰化物 (DMC)络合物催化剂 ,以X 射线衍射、元素分析、红外光谱等手段进行了表征 ,考察了该催化体系下环氧丙烷开环聚合的反应特性 ,并初步探讨了聚合反应的机理 .研究发现 ,Co Zn双金属氰化物催化剂具有很高的催化活性 ,适合于中高分子量聚醚的合成 ,但是碱性起始剂起阻聚作用 ;在该催化体系下聚合物分子量可控 ,不饱和度很低 (<0 .0 14meq g) ,分批加料聚合所得到的聚合物分子量分布较窄 (Mn Mw <1.4 ) ,而一步加料聚合所得到的聚合物分子量分布变宽 ;1 3C NMR分析表明聚合物主链具有无规立构分布的特点 ,且链节分布几乎都为头 尾方式 .聚合过程中活性链与非活性链之间可能存在一个交换反应 ;虽然聚合反应有终止 ,但与聚合物链长没有关系 ,聚合物链的终止是可逆的 .

CHARACTERISTIC FEATURE OF RING-OPENING POLYMERIZATION OF PROPYLENE OXIDE CATALYZED BY DOUBLE METAL CYANIDE COMPLEX

A double metal cyanide(DMC) complex based on Zn 3Co(CN) 6] 2 is prepared and it is characterized by IR,XRD,TGA.This catalytic system is highly active for the ring\|opening polymerization (ROP) of propylene oxide,and gives polymers that have narrow MWD(<1.40) and low unsaturation(<0.014?meq/g).The molecular weight of polymer is entirely controlled by reacted monomer to initiator molar ratio( M/I). The polymers prepared with stepwise addition of monomer exhibit narrower MWD compared with those prepared by one\|step addition of monomer. The polymerization involves a rapid exchange equilibrium between the active species and inactive chains.It has also been proved that chain termination of this catalytic system is reversible or temporary.The active centre of catalyst is electron\|accepting.The microstructure of the polymer is determined with 13 C\|NMR spectroscopy.The polymer has a random distribution of the configurational sequences and head\|to\|hail regiosequence.It is assumed that the polymerization proceeds via a cationic coordination mechanism.