Adsorption of triarm starblock copolymers based on polystyrene, poly(ethylene oxide) and poly(ϵ-caprolactone) at the solid-solution interface

Abstract

Triarm starblock copolymers of ABC type and AB diblock copolymers, where A, B and C are respectively poly(ethylene oxide) (PEO), polystyrene (PS) and poly(ϵ-caprolactone) (PCL) blocks, having molecular weights in the range 24 700–260 000, were prepared by anionic polymerization in tetrahydrofuran. The copolymer adsorption onto titanium dioxide particles in toluene was studied in the concentration range 0.1–30 g dm −3. The proton NMR experimental results indicate that the copolymers were adsorbed by titanium dioxide via the PEO block. For the diblock copolymer the measured maximum adsorbed amount Γ and the surface density σ were larger than those observed for the corresponding star copolymer. For star copolymers having the same number of repeat units of PS and PEO blocks ( N PS and N PEO) Γ and σ were found to increase with decreasing size of PCL block N PCL. Furthermore, the estimated average spacing Σ between the adsorbed chains was found to increase with N PCL, indicating that in the adsorbing layer the PCL arms were close together and stretched.