Loading polyelectrolytes onto porous microspheres: Impact of molecular and electrochemical parameters

The impact of macromolecule constitution and electrostatic dimensions on the adsorption of cationic model polyelectrolytes (PELs) onto oppositely charged porous microspheres (MSs) suspended in aqueous media is demonstrated. The contour length (L) of the PEL, the chemical structure of the substituents at the ionic group, the ionic strength of the solution (I), and the average pore radius of the microspheres (R) are considered as variable. Adsorption isotherms quantitatively reveal how PEL parameters, MS geometry, and medium characteristics affect the adsorbed amount and surface coverage. Electrostatic exclusion from pores was proved as long as the Debye length (lD) exceeded R, even if L was considerably smaller than the pore diameter. Two charge parameters (CRcalc and CRexp) and the ratio thereof (CR) were derived and served to evaluate the loading process. All three parameters are applicable to two limiting cases, first, adsorption only on the outer surface of the MS and, second, additional adsorption ins...