Neutron scattering of hydrophobically modified poly(ethylene oxide) in aqueous solutions in the presence of latex particles

The structure of aqueous solutions of hydrophobically end-capped poly(ethylene oxide), PEOM, in the presence of solid particles (latex) was investigated by small angle neutron scattering. Mono- and di-functionalised PEOMs with the same ratio of hydrophilic to aliphatic (C16H33) hydrophobic groups of molecular weights 16 000 and 32 000 g mol−1, respectively, were compared. We used solvent conditions in which either PEOM or latex were matched by varying the ratio of water to heavy water. Initially, a decrease in the scattering intensity at small angles was observed when PEOM was added to a suspension of latex at constant concentration. A peak was observed in the structure factor which indicated repulsion between particles. The position of the peak lied at a lower q value for mono-functionalised PEO than for di-functionalised PEO. This observation may be explained by the formation of bridges between aggregates by the di-functionalised PEOM. On varying the solvent, the characteristic peak of PEOM alone disappears at low polymer concentrations due to PEOM adsorption onto the latex particles but reappears at higher polymer concentrations.