离子液体中单电子转移活性自由基聚合法制备星形聚丙烯酰胺

Synthesis of Star Polyacrylamide by Single Electron Transfer Living Radical Polymerization in Ionic Liquid System

以季戊四醇为原料,合成了2,2-二溴甲基-1,3-二溴丙烷(PEBr4),并以此为四官能度引发剂,Cu0粉/三-(2-二甲氨基乙基)胺(Me6-TREN)为催化体系,在离子液体中实现了丙烯酰胺(AM)的单电子转移活性自由基聚合(SET-LRP),得到了窄分子量分布的星形聚丙烯酰胺(PAM),Mw/Mn约为1.26(MGn PC=14.1×103,转化率为43.4%)。采用1H NMR对PAM结构进行表征确认,并采用GPC测定了PAM的分子量及分子量分布;考察了水、单体/催化剂(引发剂)配比对聚合反应的影响。结果表明,少量水的加入能够加快聚合反应,使链增长速率常数由kapp p=0.042 4 h-1增加至kapp p=0.148 6 h-1;催化剂、引发剂用量越大,AM的SET-LRP的聚合反应速率越快,聚合反应的可控性越好,Mn随催化剂用量的增大及引发剂用量的减小而增大,且与理论分子量相近,分子量分布均呈下降趋势。

A single electron transfer living radical polymerization（SET-LRP） is able to rapidly achieve high molecular mass,with excellent control of molecular mass distribution,represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture.The SET-LRP of acryl amide（AM） was investigated at 40 ℃ in 1-butyl,3-methyl tetrafluoroborate（BF4） ionic liquid,using Cu0 power/tris（2-dimethylamin ethyl） amine（Me6-TREN） as catalyst,2,2-dibromomethyl-1,3-dibromopropane（PEBr4） as initiator.The polymerization showed some ＂living＂ features： the conversion and ln（[M]0/[M]） increased linearly with time as well as the number-average molecular mass increased linearly with conversion.The star polyacrylamide（sPAM） prepared via SET-LRP was characterized by GPC and 1H NMR to identify its polymerization mechanism,and the results showed that the polymer had the perfect functional chain ends and relatively low molecular mass distribution Mw/Mn≈1.26（MGPCn=14.1×103,conversion rate is 43.4%）,indicating a controlled polymerization.The effects of water,catalyst and initiator on polymerization were studied,and the dynamic experiments were carried out.A small amount of water added could accerlerate the polymerization,the apparent rate constants of propagation（kappp） were 0.04248 h-1 and 0.14869 h-1 for adding free water and 0.5 mL H2O respectively;the control of polymerization could be improved with the presence of catalyst and increasing the concentration of initiator.The polymerization rate of SET-LRP increased with the amount of catalyst and initiator.In addition,Mn increased with the amount of catalyst or decreasing the amount of initiator and was closed to the theoretical molecular mass.The molecular mass distribution showed a decreasing trend,the minimum was about 1.26.The BF4 ionic liquid was a good solvent to PEBr4 and acryl amide,and the polymers were easily separated from the catalyst.