ABSTRACT
Adsorption of molecules onto material surfaces is a fundamental process in supramolecular design for biological applications. When certain solid materials are immersed in solutions containing synthetic polymers or biopolymers, the polymers spontaneously adsorb onto the material surfaces as a result of concentration-dependent interactions. Two types of physical and chemical adsorption have been defined. The first is governed by van der Waals interactions such as London forces, dipole-dipole interactions, and so on, between the polymers and the material surfaces, without any orbital overlapping. The second involves the formation of chemical bonds or overlapping of molecular orbitals by electrostatic, hydrogen bond, or charge-transfer interactions. The classification of physical or chemical adsorption is difficult in most cases of polymer adsorptions, because various functional groups exist in polymers and on material surfaces. Some researchers in biology utilize terms such as “specific” and “nonspecific” adsorption to describe these biomolecular interactions. Specific adsorption usually includes adsorption based on multiple structurally regulated interactions, such as antibody to antigen, adsorption of sugar-binding proteins (lectins) to corresponding sugars, or other specific-bindings between biomolecules. Nonspecific adsorption includes adsorption of other molecules to various material surfaces without any specific interactions. The present section describes the basis of physical adsorption of various molecules. Although nonspecific adsorption is not strictly defined as physical adsorption, it is included here.
