Synthesis of star-comb PCE superplasticiser towards an understanding of its properties in cement pastes

Synthesis of the star-comb (also referred to as star-graft) copolymer architecture of a polycarboxylate ether or poly(acrylic acid)-co-poly(isoprenyl oxy poly(ethylene glycol) ether) (PCE) using a star chain transfer agent (CTA) with multiple mercapto groups by free radical polymerisation and its properties in cement pastes are discussed. By varying the number of mercapto groups of the star CTA, star-comb PCEs with a similar acid/ether ratio, molecular weight and anionic charge density but different arm numbers were prepared. The synthesised PCEs were characterised by proton nuclear magnetic resonance and gel permeation chromatography with a triple-detector system. It was proved that PCEs with star-comb topological structure could be successfully applied as superplasticisers. The effects of star-comb PCEs with different numbers of arms on cement paste fluidity, zeta potential and adsorption were studied. A theoretical model was developed to explain the differences in adsorption behaviour of linear-comb and star-comb PCEs on the surfaces of cement particles. This work provides useful guidance for the exploration of new topological structures of PCEs in future studies.