Hydrophilic magnetic polymer latexes. 1. Adsorption of magnetic iron oxidenanoparticles onto various cationic latexes

With a view to preparing monosized hydrophilic functional magnetic latex pa rticles based on a two-step strategy using anionic iron oxide and cationic polymer latexes, the adsorption step was systematically investigated for a better control of the subsequent encapsulation step. The iron oxide nanopar ticles were first obtained according to the classical precipitation method of ferric and ferrous chloride salt using a concentrated sodium hydroxide s olution, whereas the polystyrene (PS), P(S/N-isopropylacrylamide (NIPAM)) c ore-shell and PNIPAM latexes were produced via emulsion and precipitation p olymerizations, respectively. The polymer and inorganic colloids were then characterised. The adsorption of iron oxide nanoparticles onto the three ty pes of polymer latexes via electrostatic interaction was studied as a funct ion of iron oxide particle concentration, charge density and the cross-link ing density of the hydrophilic layer. The maximum amounts of magnetic nanop articles adsorbed onto the various latexes were found to increase in the fo llowing order: PS < P(S/NIPAM)< P(NIPAM). This significant difference is di scussed by taking into account the charge distribution in the hydrogel laye r and diffusion phenomena inside the cross-linked hydrophilic shell.