Preparation and dispersion properties of polycarbonate superplasticizers based on RAFT polymerization

Comb-like polycarbonate superplasticizers (PCEs) are widely used as a cement additive, and obtaining high-performance PCEs has become a hot topic. PCEs are usually kind of random polymers obtained by free radical solution polymerization, and thus it is hard to clarify the relationship between the properties of PCE and its structure. In this work, the block copolymers PCEs with the clear structure were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization. The relationship between the structure of PCE and its dispersion properties in cement was systematically discussed based on the flowability data of the cement paste with PCEs and the adsorption data of PCEs on the cement particles. Effects of the monomer ratio and the molecular weight on the adsorption and dispersion ability of PCEs in cement paste were studied. The results showed that the adsorption capacity and dispersion properties of PCEs in cement paste are related to the structural parameters of the polymer molecules. PCEs exhibited the optimal dispersion properties when the ratio of the monomers was 6:1 and the molecular weight was no greater than PCE-8 ( M n = 53,450, M w = 62,358).