Polycarboxylates are linear polymers with a high molecular mass (Mr ≤ 100 000) and with many carboxylate groups. They are polymers of acrylic acid or copolymers of acrylic acid and maleic acid. The polymer is used as the sodium salt (see: sodium polyacrylate).
Polycarboxylates are used as builders in detergents. Their high chelating power, even at low concentrations, reduces deposits on the laundry and inhibits the crystal growth of calcite.
Polycarboxylate ethers (PCE) are used as superplasticizers in concrete production.
Polycarboxylates are poorly biodegradable but have a low ecotoxicity. In the sewage treatment plant, the polymer remains largely in the sludge and is separated from the wastewater.
Polyamino acids like polyaspartic acid and polyglutamic acid have better biodegradability but lower chelating performance than polyacrylates. They are also less stable towards heat and alkali. Since they contain nitrogen, they contribute to eutrophication.
Polycarboxylate superplasticizers (PCEs) are comb-shaped polymers with an anionic backbone and several nonionic pendant chains, which typically are comprised of polyethylene glycols.
In this study, the synthesis of a new type of superplasticizer is presented, which does not exhibit the typical comb-shaped form of PCEs but is built up from a linear polyetheramine and a hyperbranched polyglycerol scaffold, which was carboxymethylated in the periphery. 1H/13C NMR and FT-IR spectroscopy and size exclusion chromatography were employed for the characterization of the polymers.
Furthermore, their dispersing performance and “slump retention” capability were investigated in cement pastes. Adsorption and zeta potential measurements as well as heat flow calorimetry were conducted to gain more insight into the interaction of the polymers with cement. It was found that such non-comb-shaped polymers are highly effective cement dispersants.
Moreover, the hyperbranched superplasticizers exhibited high robustness toward alkali sulfates and maintained the fluidity much longer, compared to a conventional comb-shaped PCE.