Polycarboxylate ethers (PCE) are also called PCs or comb polymers. They are the most recent development and unlike SNFs and SMFs, which are essentially a single structure, PCEs are a family of products with significantly different chemical structures. 

The backbone polymer is typically based on the polymerization of acrylic acid but this can be substituted or replaced with other monomer groups and can be used to modify the number of carboxylate groups along the polymer backbone. The carboxylate group is normally neutralized as the sodium salt and takes on a negative charge in solution as the Na+ dissociates. This provides the attachment point for the admixture to adsorb onto the cement surface.

The co-polymer is a polyether, combinations of polyether can be used and the molecular weight varied, n typically ranging from 20 to 80 units. This together with the number of polyether groups substituted along the chain and the length of the chain can give a significant range of properties. This allows the basic copolymer to be tailored for, say, high early strength for pre-cast or for workability retention for readymix even before other chemicals are blended in. The polyether is the part responsible for the dispersion of the cement particles and works by a steric effect.

Steric stabilization is the main mechanism in PCE superplasticizers. These molecules carry–CO2Na groups which, in water, dissociate into –CO2− and Na+. The –CO2− remains attached to the admixture and carries a moderate negative charge that is used to attach the admixture to the cement.

When water is added to cement, the grains are not uniformly dispersed throughout the water but tend to form into small lumps or flocs. These flocs trap water within them causing the mix to be less mobile and fluid than would be the case if the cement were in the form of individual grains. Admixtures adsorb onto the cement surfaces and break up the flocs, leaving individual cement grains, which can pass each other easily, making the mix more fluid.

There is no change in volume of the mix, just the release of water trapped within the floc and the ability of individual cement grains to reorientate to make more efficient use of all the available volume without inter-particle contact. Not only has the fluidity increased, but with water surrounding the whole grain, hydration is more efficient.