Tethered chains in polymer microstructures

Tethered polymer chains refers to macromolecular chains that are attached into microstructures by their ends. Highly branched polymers, polymer micelles and end-grafted chains on surfaces are a few examples. This review brings out the common features of these seemingly widely disparate microstructures. Tethering can be reversible or irreversible and is frequently sufficiently dense that the chains are crowded. Densely tethered chains stretch to alleviate the interactions caused by crowding. They thus exhibit deformed configurations at equilibrium. These effects of tethering on the structure of the polymer chains are reflected in distinctive behavior and properties of microstructures containing tethered chains. The topics we cover are: structure, in which the relationships of the free energy and characteristic dimensions of tethered chains to chain contour length, grafting density and geometry are developed; aggregation, by which we mean equilibrium microstructures formed by self-assembly such as micelles, adsorbed layers or ordered phases in block copolymers, where we can illustrate how the structural concepts come into play; phase behavior, which occurs, for example, in structures having more than one tethered component, such as mixed micelles; block copolymer melts, which are important systems which manifest the characteristics of tethered chains in both the aggregation and phase behavior, interactions, in which the behavior of two tethered layers in contact is explored, a subject of importance to applications involving colloidal stability; and kinetics and dynamics, where the chain deformation arising from tethering affects the kinetics of assembly and exchange processes and the entanglement behavior.