聚羧酸减水剂的RAFT水相合成研究

Synthesis of polycarboxylate superplasticizers with RAFT aqueous polymerization

采用水溶性的可逆加成-断裂链转移自由基聚合(RAFT)链转移剂,在水相中引发甲基丙烯酸(MAA)、聚乙二醇单甲醚甲基丙烯酸酯(MPEG)聚合,制备聚羧酸减水剂。核磁共振氢谱、红外光谱和凝胶渗透色谱分析表明,所合成的聚羧酸减水剂结构可控、分子质量分布较窄。水泥净浆试验结果表明:在n(CPADB)∶n(MAA+MPEG)=1∶(70~200)范围内,合成聚羧酸减水剂的分散性基本相当;CPADB用量过少或过多,均会降低减水剂的分散性。在n(CPADB)∶n(MAA+MPEG)一定的条件下,酸酯比[n(MAA)∶n(MPEG)]越大,羧酸的密度越高,合成聚羧酸减水剂的分散性越好。

Polycarboxylate superplasticizer was synthesized in aqueous media by applying the reversible addition-fragmentation chain transfer(RAFT)polymerization with methacrylic acid(MAA)and poly(ethylene glycol)methyl ether methacrylate(MPEG)as the monomers.The obtained polycarboxylate superplasticizer has controlled structure and relative narrow distribution of molecular mass as revealed by 1HNMR,FT-IR and GPC.Results of cement flow experiments illustrated that the dispersibility of polycarboxylate superplasticizer is basically equivalent within the range of n(CPADB)∶n(MAA+MPEG)=1∶(70~200).Too small or high of CPADB dosage both led to inferior water-reducing ability.In addition,it was found when n(CPADB)∶n(MAA+MPEG)was kept constant,a higher ratio of MAA to MPEG,which demonstrated higher carboxylic acid density,exhibited a better water-reducing functionality.