Synthesis,Characterization And Properties Of Side Chain Hyperbranched Polycarboxylate Superplasticizer

Polycarboxylate Superplasticizer（PCE）,as a new generation of high-efficiency water reducing agent,has the advantages of high water reduction,high slump,low dosage,etc.,which can be used to prepare high-performance concrete（HPC）.Hyperbranched polymer is a kind of polymer with special macromolecular structure,its molecular structure is between linear and spherical molecules.Due to the existence of many active groups at the terminal,hyperbranched polymer has more excellent properties,such as high solubility,high chemical reactivity and low viscosity,compared with linear polymer.In this paper,based on the water-reducing dispersion mechanism and excellent molecular design of PCE,the side-chain hyperbranched polycarboxylate superplasticizer（TAHB-PCE）was designed and synthesized,which broke the traditional comb structure of PCE.Compared with comb PCE,it can be used in the same molecular weight and carboxylic acid density.By increasing the density of the side chain of polyoxyethylene ether,it has better water reducing and dispersing performance than comb PCE.Firstly,chlorinated polyethylene glycol monomethyl ether（Cl-MPEG）was synthesized from polyethylene glycol monomethyl ether（MPEG）and sulfinyl chloride as raw materials,and then the intermediate MPEG-ETA was obtained by long link grafting with ethanolamine as the core.Finally,the C=C was introduced by acryyl chloride.Two-arm hyperbranched polyoxyethylene ether large monomer（TAHBPE）was synthesized.FT-IR,¹H-NMR,¹³C-NMR and MS were used to characterize and confirm the structure of the intermediate and final products.FT-IR,¹H-NMR and ¹³C-NMR results showed that the intermediate chlorinated polyethylene glycol monomethyl ether（Cl-MPEG）was in line with the expected design.FT-IR and MS results showed that the structure of TAHBPE was consistent with the expected design.TAHB-PCEs was synthesized by free radical copolymerization of TAHBPE with small monomer acrylic acid（AA）and chain transfer agent sodium methallyl sulfonate acid（MAS）in aqueous solution under the initiation of ammonium persulfate（APS）initiator,and the main chain length of TAHB-PCE was regulated by changing theamount of MAS.The optimal molecular weight was determined by gel chromatography and fluidity test.The water-reducing dispersive properties,rheological properties,surface tension and contact Angle of TAHB-PCEs were studied,and compared with comb polycarboxylate acid（TPCEs）,the structure-activity relationship of TAHB-PCEs was discussed based on the structure and properties of TAHB-PCEs.The results show that under the reaction conditions studied.The optimum synthesis ratio of side chain polymerization degree 11,TAHB-PCEs（TAHB-PCE 11）and side chain polymerization degree 22 TAHB-PCES（TAHB-PCE 22）was mol _AA:mol _TAHBPE:mol _MAS=2.5:1:0.72.The initial fluidity of the net slurry of TAHB-PCE 11 and TAHB-PCE 22 can reach 315.5 mm and 335.0 mm,which is 12mm and 31.5 mm higher than TPCE 303.5 mm,respectively,when the dosage is0.3%.TAHBPE has better fluidity than TPCE.The surface tension test results showed that the surface tension of pure water mixed with TPCE decreased from 71.82m N/m to 46.23 m N/m,while the surface tension of solution mixed with TAHB-PCE decreased to about 34 m N/m,12.23 m N/m lower than that of TPCE.The results of contact Angle test show that when the dosage of water reducer is 12wt%,TPCE can reduce the contact Angle of pure water from 82.03°to 70.23°,while TAHB-PCE with side chain polymerization degree 11 can reduce the contact Angle to 65.3°,and TAHB-PCE with side chain polymerization degree 22 can reduce the contact Angle to63.33°.The results of surface tension and contact Angle test prove that TAHB-PCE has better wettability on cement surface than traditional comb PCE,and the rheological properties also indicate that TAHB-PCE has higher fluidity and lower viscosity.Although the side chain length of TAHB-PCE synthesized in this paper is shorter than that of traditional comb PCE,the side chain density increases,the surface tension and surface energy decrease,and it has better wettability on cement surface.In addition,the steric resistance of TAHB-PCE side chain increases after hyperbranched polymer,and it also has the advantages of high solubility and low viscosity of hyperbranched polymer.TAHB-PCE has a better dispersion effect.