Statistical thermodynamics of block copolymer adsorption. Part 2.—Effect of chain composition on the adsorbed amount and layer thickness

Abstract

Recently, we presented a self-consistent field theory for the adsorption of block copolymers [O. A. Evers, PhD Thesis, (Wageningen, 1990)]. The physical background of this theory is briefly reviewed and a number of results on the adsorbed amount and the hydrodynamic layer thickness of adsorbed di- and tri-block copolymers are presented.

The adsorbed amount and the hydrodynamic layer thickness of adsorbed block copolymers depend strongly on the chain composition. When the total length of a diblock copolymer is kept constant, a maximum is found in the adsorbed amount as a function of the fraction of adsorbing segments. This maximum is found at a lower fraction of adsorbing segments with increasing chain length, bulk solution concentration and surface affinity.

Usually thick adsorbed layers are found. For diblock copolymers the hydrodynamic layer thickness is of the order of 10–30% of the length of the non-adsorbing block, depending on the solvent quality.

For BAB-triblock copolymers with adsorbing A-segments and non-adsorbing B-segments we find lower adsorbed amounts as compared to an AB-block copolymer with the same number of A- and B-segments.