Preparation Of Comb Block Polycarboxylate Dispersant By RAFT Polymerization And Its Application In Cement

In recent years,with the development of building structure to scale and high function,the demand for cement and concrete and high-performance requirements have also increasing.In cement science,the performance of cement products is usually improved by adding dispersant,retarder and other additives.The common polycarboxylate dispersant is synthesized by free radical aqueous solution polymerization.The molecular structure is usually comb-like and the arrangement of monomers in its molecular structure is random,and its fine structure and molecular sequence are vague.It is precisely because the common polycarboxylate dispersant synthesis technology cannot obtain a copolymer with a clear molecular structure,it is impossible to establish the correct relationship between the molecular structure of the polycarboxylate dispersant and its dispersion performance,so that it is impossible to synthesize high-performance targeted Polycarboxylate dispersant.Reversible addition-fragmentation chain transfer polymerization(RAFT)is a widely used controllable free radical living polymerization.It is currently one of the best polymerization methods for preparing copolymers with a clear molecular structure.Its synthesis method is relatively mature.Structural parameters such as the monomer ratio and molecular weight of the polycarboxylate dispersant have an important influence on its dispersion performance.In order to accurately explore the influence of the molecular structure parameters of polycarboxylate dispersant on the performance of dispersing cement particles,this paper synthesizes different types of block polycarboxylate dispersants through RAFT polymerization,and investigates the influence of their structural parameters on the performance of dispersing cement particles.(1)In this work,monomer acrylic acid(AA)and isoprenyl oxy polyethylene glycol ether(TPEG)were used to synthesize block PCEs by RAFT polymerization.The monomer ratio and molecular weight structure were explored.The influence of parameters on the dispersion properties of PCEs molecules.The chemical structure of PCEs were characterized by Fourier transform infrared spectroscopy(FT-IR),~1H nuclear magnetic resonance(~1H-NMR)and Gel permeation chromatography(GPC).By analyzing the fluidity data of cement paste blended with PCEs and the adsorption data of PCEs molecules on cement particles,the relationship between the structure of PCEs and its dispersion in cement paste was systematically discussed.The effect of monomer ratio and molecular weight structure parameters on the dispersion ability of PCEs molecules in cement paste was studied.The results show that the adsorption capacity and dispersion performance of PCEs in cement paste are related to the structural parameters of polymer molecules.When the monomer ratio is 6:1 and the molecular weight is not greater than PCE-8 molecules(Mn=53,450,Mw=62,358),PCEs show the best dispersion performance.(2)In this work,monomer tert-butyl acrylate(t BA)and TPEG were used to synthesize A_aB_bA_ctriblock polycarboxylate dispersants(PCs)by RAFT polymerization.The monomers were explored The influence of ratio and monomer ratio at both ends(a=c or a≠c)on the dispersion properties of PCs molecules.The chemical structure of PCs was characterized by FT-IR,~1H-NMR and GPC,and the molecular structure of the polymer prepared by the RAFT reaction conforms to the pre-design.By analyzing the fluidity data of cement paste mixed with PCs and the adsorption data of PCs molecules on cement particles,the relationship between the structure of PCs and their dispersion performance in cement paste was systematically discussed.The results show that the adsorption capacity and dispersion performance of PCs in cement slurry are related to the structural parameters of polymer molecules.When the monomer ratio is 5:1 and a:c=4:1,PCs show the best dispersion performance.