Nonselective adsorption of block copolymers and the effect of block incompatibility

The adsorbed amount and the hydrodynamic layer thickness of two series of block copolymers and the corresponding homopolymers on silica were determined. Sire used diblock copolymers of poly(vinyl methyl ether) and poly(2-ethyl-2-oxazoline) and tri- and diblock copolymers of poly(2-methyl-2-oxazoline) and poly(ethylene oxide). The diblock copolymers of poly(ethylene oxide) and poly(2-methyl-2-oxazoline) were obtained by polymerization of a-methyl-a-oxazoline initiated by the tosylate of poly(ethylene glycol) monomethyl ether. The difference between the adsorption energies of the segments is found to be small: the block copolymer adsorption is nonselective. The adsorbed amount as a function of block copolymer composition shows a maximum at a composition where the longest block is also the strongest adsorbing block. The adsorbed amounts and the layer thicknesses are relatively low. Similar results are obtained with numerical self-consistent field calculations for nonselective adsorption for the case when the different blocks are incompatible. The typical anchor-buoy structure of the adsorbed layer is maintained, albeit less explicit than that found for selective adsorption.