Study On The Synthesis Of GO-g-POE-b-PAA And Its Application On Modifying Cement-based Materials

In this study,RAFT reagents[4-cyano-4-（phenylcarbonothioylthio）pentanoic acid（CDTB）or 2-（（（Dodecylthio）carbonothioyl）thio）-2-methylpropanoic acid（DCMA）]were respectively constructed on graphene oxide（GO）surface by esterification reaction to synthesize GO-RAFT（GR）.Poly（poly（ethylene glycol）methyl ether methacrylate）（POE）and block copolymerized poly（acrylic acid）（POE-b-PAA）were grafted onto GO surface in order to prepare GO-g-POE（GE）and GO-g-POE-b-PAA（GEA）.GO,GR,GE and GEA were analyzed by Gel Permeation Chromatography（GPC）,Thermal Gravimetric Analyzer（TG）,Fourier Transform Infrared Spectrometer（FT-IR）,X-ray Photoelectron Spectroscopy（XPS）,Laser Raman Spectrometer（Raman）,Atomic Force Microscopy（AFM）,Scanning Electron Microscope（SEM）and Transmission Electron Microscope（TEM）.GO with high oxidation degree was used to graft RAFT reagent DCMA for subsequent synthesis.GE was synthesized by using DMF phase and poly（ethylene glycol）methyl ether methacrylate（OE）with molecular weight of 950 g/mol.POE chains grafted onto GO surface owned high molecular weight and narrow molecular weight distribution.With the increase of m[OE]/m[GR]and reaction time,the molecular weight of POE chains grafted onto GO surface increased and the molecular weight distribution of POE chains became wider.With the increase of m[AA]/m[GE]and reaction time,the molecular weight of POE-b-PAA chains grafted onto GO surface increased and the molecular weight distribution of POE-b-PAA chains became wider.The effects of different concentrations of the solution containing Na⁺,K⁺,Ca²⁺and Na OH solution with different pH values on GO deposition were studied by Zeta Potential Analyzer and XDLVO theory,and it was found that Ca²⁺had an obvious effect on GO coagulation.Through Zeta Potential Analyzer and Laser Light Scattering System（DLS）,it was found that GEA improved the dispersion of nanosheets in the cement slurry filtrate.The dispersity of GE in the cement slurry filtrate increased when the molecular weight of grafted POE chains increased.The dispersity of GEA in the cement slurry filtrate increased when the molecular weight of grafted POE-b-PAA chains increased.The results of hydration heat,TG,X-Ray Diffractometer（XRD）,Ratio Surface and Porosity Analyzer（BET）and SEM showed that GEA promoted cement hydration,and the hardened cement slurry with GEA owned small porosity and compact hydration products.The compressive strength of the cement mortar with 0.015 wt%GEA cured for 3,7 and 28 days were increased by 9.13%,17.02%and 17.40%,and the flexural strength by 6.20%,9.40%and 11.41%,respectively.The mechanical strength of cement-based materials increased when the additive amount of GEA increased.However,the strengthening and toughening effect of GEA on cement-based materials decreased when the additive amount of GEA reached 0.06 wt%.