Theory of polymer adsorption at interfaces

Previous theories valid for polymer chains with large loops protruding into the solvent are developed. Interaction in various layers parallel to the interface is calculated according to the Flory‐Huggins theory. Excluded volume effects are shown to be so small that they can be neglected. The adsorption isotherm is expressed in two parameters: one for the partition function for adsorbed segments and the other one for the stiffness of the chains. For adsorption from good solvents, the fraction of segments in the surface layer is large and the loops are small. For adsorption from theta‐solvents, the fraction of segments in the surface layer is small and the loops are large. The trends are in agreement with those experimentally observed, but the observed layer thickness is larger than the theoretically deduced upper limit.