Early polycarboxylate superplasticizer monomers were ester-based products, with methyl polyethylene glycol ether (MPEG) as the macromonomer, as shown in Figure 2. When synthesizing polycarboxylate superplasticizers using such macromonomers, two-step reactions—esterification and polymerization—were required, making the process relatively complex. These have now been gradually replaced by ether-based macromonomers.
Ether-based polycarboxylate water-reducing agent macro-monomers are currently the mainstream macro-monomer products. These macro-monomers are primarily synthesized by ethoxylation reactions of small-molecule unsaturated alcohol initiators with varying structures, resulting in polyethylene glycol ethers with terminal double bonds. Depending on the molecular structure of the initiators, the synthesized macro-monomers can be classified into three types: 3-carbon vinyl alcohol-based macro-monomers (allyl polyethylene glycol ether-APEG), 4-carbon and 5-carbon vinyl alcohol-based macro-monomers (isobutyl polyethylene glycol ether-HPEG, isopentyl polyethylene glycol ether-TPEG), and 2+2 and 2+4 vinyl ether-based macro-monomers (EPEG, VPEG).
On the basis of existing research, the author's team has developed a new type of ethylene ether based polycarboxylate superplasticizer monomer: ethylene glycol monovinyl polyethylene glycol ether (EPEG, 2+2 monomer).
By comparing the electron cloud density and spatial hindrance of unsaturated double bond structures in different monomer molecules, the high or low polymerization activity of unsaturated double bonds in different monomers was determined.
Due to the single substitution structure of the double bond in the molecule, the spatial resistance of the polyether side chain swing is further reduced, making the swing of the polyether side chain more free and the range of activity larger; The increase in the degree of freedom of the polyether side chain swing improves the wrapping and entanglement of the polyether side chain, resulting in a polycarboxylate superplasticizer with higher adaptability, especially for situations where the quality of sand and gravel is poor and the mud content is high.
