Synthesis of block polycarboxylate copolymer and its application in a cement system

The sequence structure of polymers plays an important role in determining their performance. However, existing polycarboxylates mostly have a broad molecular weight distribution and the sequence structure is randomly distributed. In this work, a novel water-soluble block copolymer made of poly(ethylene glycol) methyl ether methacrylate (OEGMA) and acrylic acid (AA) was designed using reversible addition-fragmentation chain transfer polymerisation. Structural information of the block polycarboxylate was characterised by gel permeation chromatography and proton nuclear magnetic resonance. The effects of molar ratio of AA to OEGMA on flowability, zeta potential and adsorption in cement paste were studied. It was proved that polycarboxylate with a block distribution could be successfully applied as a superplasticiser. Furthermore, the length of the two blocks in the block distribution influenced the zeta potential and adsorption of the superplasticiser onto cement particle surfaces, and thereby the workability of cementitious materials. The knowledge gained from this work may be used in the design of superplasticisers for optimal performance in some specific applications.