The interactions of supramolecular systems often depend on small and complex molecules. It is tempting though dangerous to apply polymer theory to these molecules that are normally considered to be too small to be polymers and too large to be rigid. Here, forces and adhesions between surfaces bearing several types of such molecules with both flexible and rigid parts are measured. The force/distance profiles follow closely the description given by polymer theory. It is shown for a wide variety of systems containing these molecules that if one obtains an effective radius of gyration R-g of the molecules, polymer theory can be used to predict their adhesion energy. Conversely, if the adhesion energy for bilayers containing such small and complex molecules is measured, polymer theory allows to deduce the effective R-g of the molecule.