| A N-hydroxyethyl-3-amino-N,N-dipropyl ester was synthesized by methyl acrylate and ethanolamine through Michael addition reaction. The first and second generation ester terminated hyperbranched poly(amine-ester) were obtained by malonic acid and N-hydroxyethyl-3-amino-N,N-dipropyl ester through esterification and transesterification. Macroinitiator bromo-terminated hyperbranched poly(amine - ester) was obtained by ester terminated hyperbranched poly(amine-ester) and 2-bromoethanol through transesterification. Hyperbranched-star type polycarboxylate superplasticizers (HPC) was obtained through atom transfer radical polymerization with cuprous bromide and 2'2-bipyridine used as catalyst and complexing agent, acrylic acid and methoxy terminated allylic polyethylene glycol as monomers, secondary water as solvent, bromo-terminated hyperbranched poly(amine - ester) as macroinitiator. Number of ordinary superplasticizer molecules were grafted in a macromolecular HPC. A star-shaped emanative structure was formed which increases the contact area and bonding force between superplasticizer and cement particles, and the steric repulsion of superplasticizer was greatly increased either. Cement particles with better dispersion were harder to get together. HPC was a breakthrough to the existing structure of superplasticizer.Orthogonal experimental was used to obtain the best synthetic conditions of bromo-terminated hyperbranched poly (amine-ester) and the initial flow of paste of OPC with APC was used as index to obtain the optimum conditions of HPC through orthogonal experimental. The best conditions of bromo-terminated hyperbranched poly (amine-ester): toluenesulfonic acid dosage was 5% wt, the reaction time was 7h, the reaction temperature was 110℃, the best conditions of HPC: the molar ratio of AA, CPEG was chosen as 3.5:1.0, the polymerization degree of CPEG was 27.HPC, N-hydroxyethyl-3-amino-N,N-dipropyl ester and ester terminated hyperbranched poly(amine-ester) were characterized by FTIR spectra, NMR spectroscopy, elemental analysis and surface tention. Besides, effect of content of CPEG and its polymerizationon degre on perforamces of HPC in OPC and SAC was investigated. Adsorption and Zeta potential were also tested for investigating the the main mechanism for HPC in OPC and SAC. Results showed that steric repulsion between the cement particles carrying adsorbed polymer molecules is the main mechanism for dispersion.In order to evaluate the performance of HPC, a commercial anionic superplasticizer were also used for assessing the performances. Results showed that water-reducing rate, paste fluidity, mechanical properties and adsorption of HPC in OPC and SAC were greater than the commercial anionic superplasticizer. |
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