| Abstract: | The reactivity ratio of monomer and the microstructure of copolymer as polycarboxylate ether (PCE) superplasticizer were investigated.Polycarboxylate ethers (PCEs) were synthesized from methyl allyl polyethylene glycol (MAPEG,M_w=2 400 g/mol) and methacrylic acid (MAA) via aqueous free radical copolymerization in low conversion (P20%).Gel permeation chromatography (GPC) and high performance liquid chromatography (HPLC) were used to track the residual concentration of the reactants and the amount of copolymer formed during the copolymerization.The reactivity ratios of monomers,MAPEG and MAA,were determined as r_(1(MAPEG))=0.0489 and r_(2(MAA))=1.6173,respectively,by employing the K-T and YBR methods.According to the obtained monomer reactivity results,the sequence distribution of the copolymer,the number average length of MAA in the polymerisate were found to decline with the decrease of the mole fraction of MAA in the polymerization system.As a result,the distribution of chain segments becomes narrower and the copolymer structure becomes more uniform.Therefore,uniform polymers could be obtained by slowly adding MAA monomer during copolymerization process. |
