Adsorption of di-and triblock copolymers with functionalized butadiene-styrene blocks from dilute solution

Abstract

The adsorption behaviour of functionalized polystyrene- block-polybutadiene diblock copolymers, P(S- b-B), and polybutadiene- block-polystyrene- block-polybutadiene triblock copolymers, P(B- b-S-b-B), from dilute solutions in toluene onto silicon wafers was investigated by means of null-ellipsometry. Polar 4-(3,5-dioxo- 1,2,4-triazolidin-4-yl) benzoic acid groups (urazole groups) were attached randomly to the butadiene blocks. The PS blocks and the PB blocks adsorb not on the substrate surface, but only on the polar functional groups. It was verified that the adsorbed amount does not depend on the number of functional groups nor on the degree of polymerization of the polybutadiene block within the investigated range. The adsorption isotherms for the di- and triblock copolymers are compared. The plateau value obtained for the diblock copolymers is nearly 50% higher than that for the corresponding triblock copolymers. This difference is explained based on different conformational states of the adsorbed chains, in particular by loop formation of the triblock copolymers. The adsorption kinetics reveals two regimes: a Fickian behaviour at the beginning and a slower process after the formation of a dense surface coverage.