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Title: Experimental and Theoretical Investigation on the Adsorbed Layer Thickness of PCE Comb Polymers

Author(s): Johann Plank, Johannes Stecher, Constantin Tiemeyer

Publication: Symposium Paper

Volume: 354


Appears on pages(s): 1-12

Keywords: polycarboxylate; superplasticizer; adsorption; cement; steric hindrance; adsorbed conformation; molecular dynamics (MD) simulation; dynamic light scattering (DLS); nanoparticles

DOI: 10.14359/51736057

Date: 7/1/2022

The dosage-dependent development of the adsorbed layer thickness (ALT) of two polycondensate (BNS, AFS), four polycarboxylate (23MPEG6, 45MPEG6, 52IPEG2, 52IPEG6), and one phosphate comb polymer (45MPEG-P3) was investigated via dynamic light scattering technique using cationic polystyrene nanoparticles as substrate. It was found that polycondensates develop very thin adsorbed layers [0.3 - 0.6 nm (1.2 - 2.4 × 10-8 in.)] whereas PCEs produce layers of ~ 2.5 - 8 nm (9.8 - 31 × 10-8 in.). These values are larger than those reported previously from AFM and XPS measurements but correlate well with results from molecular dynamics simulations. For PCE molecules, the side chain length exercises the most significant effect on the adsorbed layer thickness while the grafting density has less impact. Furthermore, stronger anchor groups such as the phosphate copolymer produce more dense polymer layers and hence higher ALT values which explain their excellent dispersing effectiveness. Spread flow tests using cement paste revealed a relatively close relationship between paste fluidity and ALT.