聚羧酸保坍剂分子序列结构对其性能的影响

The influence of molecular sequence structure of polycarboxylate ether slump retaining agent on its performance

通过普通自由基聚合合成侧链密度不同的无规序列结构聚羧酸保坍剂PCE-1、PCE-2;通过可逆加成-碎裂链转移聚合(RAFT)合成侧链在主链上分布形式分别为“外密内疏”和“外疏内密”梯度序列结构的聚羧酸保坍剂PCE-3、PCE-4。通过凝胶渗透色谱仪(GPC)测试证明PCE-3、PCE-4的分子质量与转化率呈线性关系,符合“活性”聚合特征。净浆和混凝土试验发现,各减水剂分散性能排序为PCE-4<PCE-1<PCE-2<PCE-3,即“外密内疏”的序列结构最适合发挥PCE的分散性,而“外疏内密”不适合作为PCE的结构。含蒙脱土的净浆试验表明,具有“紧密”侧链序列的PCE-1、PCE-3有着更好的抗泥效果。吸附试验表明,吸附能力排序为PCE-4<PCE-3<PCE-1≈PCE-2。

Two polycarboxylate ether(PCE)slump retaining agents of PCE-1/PCE-2 with a random sequence structure were synthesized by conventional free radical polymerization in this article,which had different side chain density distributions.PCE-3/PCE-4 with gradient sequence structure were synthesized by reversible addition-fragmentation chain transfer polymerization(RAFT),and their side chain distribution forms are"outer dense inner sparse"and"outer sparse inner dense",respectively.The gel permeation chromatography(GPC)test showed that the molecular weight of PCE-3/PCE-4 increased linearly with the conversion rate,which conformed to the"living"polymerization characteristics.Through cement paste and concrete tests,it was found that their dispersion performance was ranked as PCE-4<PCE-1<PCE-2<PCE-3,indicating that the sequence structure of"outer dense and inner sparse"is most suitable for exerting the dispersion ability of PCE,while"outer sparse and inner dense"is not suitable as the structure of PCE.The montmorillonite-contained cement paste test showed that PCE molecules with a"tight"side chain sequence(PCE-1/PCE-3)have better clay resistance.The adsorption test results indicate that their adsorption capacity is ranked as PCE-4<PCE-3<PCE-1≈PCE-2.