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Interpolyelectrolyte complexes of a linear cationic polymer poly(diallyldimethylammonium chloride) and anionic microgel particles with carboxyl groups in a pH 6 buffer solution are presented. Dispersions of the microgel and its complexes—negatively charged with a 3-fold molar excess of the anionic groups of the microgel and positively charged with a 3-fold molar excess of the cationic groups of the polycation—retain aggregative stability for six months. When applying 1 wt % dispersions of the microgel and complex on the surface of the soil with a high sand content, polymer-soil coatings with a mechanical strength of 19 to 61 kg/m2 depending on the composition of the dispersion are formed. These indicators significantly exceed those for coatings obtained by applying a 1 wt % solution of a linear anionic polymer, poly(acrylic acid), on the soil surface. Coatings involving microgel and its complexes remain stable at an air flow rate of 190 km/h. more...

The initial-stage dynamics of flocculation of positively charged latex particles induced by polyelectrolytes (PEs) and polyelectrolyte complexes (PECs), composed of linear polyacrylic acid (PAA) and a PAA-based hydrophilic microgel (PAA#) with a small amount of a linear polycation, was comparatively analyzed by applying the standardized colloidal mixing procedure. Based on the rate of flocculation, this method allows us to investigate the dynamics of flocculation immediately after the onset. In addition to confirming the prediction made regarding the initial rate of flocculation with linear polyanions-which was mostly similar to that observed in negatively charged colloids with positively charged PEs-we have confirmed two important new results regarding the microgel: (1) the increase of the initial rate is less markedly affected by the microgel concentration than by the linear polymer concentration, which can be explained by the fact that the three-dimensional (3D) cross-linked structure of the microgel that does not deform as easily as the linear structure upon touching the colloidal surface; and (2) there is a remarkable increase of the initial rate due to the contribution of instant aggregation of the negatively charged microgel induced by the polycation adsorption. These results suggest the significance of state and formation dynamics of PECs prior to reaching the surface of targeted colloidal particles for the intension of effective flocculation. These aspects are not treated so far in the dynamic process of flocculation. more...

The preparation of electrostatic complexes between a cationic polymer, poly(diallyldimethylammonium chloride), and natural polyanions, potassium humates, is described. The polycomplexes remain stable in the aqueous solution for a long time (up to 3 months) or form precipitates that can be easily resuspended when the sample is shaken. When aqueous solutions/suspensions of polycomplexes are applied on the sand surface, polymer-sand coatings (crusts) are formed, the mechanical strength of which increases with increasing content of poly(diallyldimethylammonium chloride) in the polycomplex. The greatest resistance to water (water resistance) is exhibited by crusts with a high proportion of mutually neutralized sections of both polymers. For such crusts, sand loss during watering is in the range from 0 to 2%. The developed multicomplex formulations can be used to stabilize soil and ground against water and wind erosion. more...

Soil erosion is a global problem with grave social, economic and ecological consequences. To stabilize the top soil layer, various approaches have been developed, including the use of synthetic and natural water-soluble polymers capable of binding to soil particles and forming a protective layer (crust) on the topsoil. Individual water-soluble polymers give crusts which lose mechanical stability after re-watering. We describe in the article effective stabilizers of model unstructured soil, sand, “polyelectrolyte complexes” (PECs), composed of two oppositely charged ionic polymers (polyelectrolytes), cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic potassium humates (PH). By varying the PDADMAC-to-PH ratio, the total charge of PECs and their solubility in water was adjusted. The PECs as well as PDADMAC and PH were deposited on the surface of monomineral quartz sand, with a mean diameter of particles from 0.15 up to 2.1 mm. After drying, polymer-sand crusts were formed; their mechanical strength increased upon elevating the cationic content in the polymer formulation. Re-watering caused both polyelectrolytes and PECs with a great excess of cationic or anionic groups to be removed from the crusts, which was additionally accompanied by loss of sand and decrease in the mechanical strength of the crust. The slightly positive PECs with a significant degree of mutually neutralized charges (“hydrophobized” blocks) formed the most stable crusts due to electrostatic and hydrophobic contacts with sand particles. A correlation was thus revealed between the PEC composition and the anti-erosion resistance of the polymer-sand crusts. It is shown that the use of non-stoichiometric polycomplexes makes it possible to manipulate the mechanical strength of the resulting coatings. The described approach is promising for fabrication of polymer formulations for environmental protection, conservation/rehabilitation of landfill sites, desertification control, anti-erosion treatment of agricultural land, conservation of mining dumps, treatment of road slopes, etc. more...