Non-stoichiometric interpolyelectrolyte complexes: Promising candidates for protection of soils

This paper describes electrostatic interaction (complexation) of two oppositely charged linear polyelectrolytes, an anionic poly(acrylic acid) and a cationic poly(diallyldimethylammonium chloride). In the excess of the anionic polymer, the complexation results in formation of non-stoichiometric interpolyelectrolyte complex (NIPEC) which is actually a block copolymer with hydrophilic regions represented by free (unbound) anionic units and hydrophobic fragments of mutually neutralized anionic and cationic units. A negative charge renders the colloidal stability to NIPEC species in aqueous solutions while ensuring their binding to heavy metal ions and positive dispersed particles. In the lab test, a NIPEC formulation (a NIPEC species aqueous solution), being deposited over a top of sod-podzolic soil with the aggregate size of 0.2 mm and less, ensures a protective NIPEC-soil layer (crust) via electrostatic and hydrophobic interactions of NIPEC species with the soil aggregates. The hardness of the NIPEC-soil crust is as more as 40 times higher than the hardness of the initial (untreated) soil, while the crust does not prevent water infiltration. These findings make NIPEC formulations promising binders for stabilization of the soil at a wind speed of 10–12 m/s. The crust seems to sustain water erosion as well. Additionally, NIPECs show a great capacity to heavy metal ions.