A microstructural analysis of isoprenol ether-based polycarboxylates and the impact of structural motifs on the dispersing effectiveness

Generally, polycarboxylate superplasticizers (PCEs) are synthesized via aqueous free radical copolymerization. The conditions during copolymerization such as relative reactivity and feeding mode and ratio of monomers can cause different monomer sequences in the final product. In this study, the sequence of monomers in PCE polymers synthesized from acrylic acid and isoprenyloxy polyethylene glycol (IPEG) macromonomer was characterized by 13C nuclear magnetic resonance (NMR) spectroscopy. Three different triads of monomer sequences (EAE, AAE and AAA; E = ether, A = acid monomer) were detected. It was found that IPEG PCEs predominantly contain the structural motifs of AAE and EAE, and less of AAA. Higher additions of acrylic acid do not incorporate into the structure of PCE, but convert to HMW polyacrylate as by-product instead. A PCE with optimal dispersing effectiveness was achieved at high contents of IPEG macromonomer, a molecular weight (Mw) around 40,000 Da and narrow molecular weight distribution.