Topological Polymer Chemistry Enters Surface Science: The Interfacial, Physico-Chemical Properties of Linear, Cyclic and Loops Brushes

The application of distinctive polymer topologies, beyond linearity, to yield cyclic and “loops”-forming surfacegrafted polymer assemblies, enables a broad modulation of highly relevant, interfacial, physicochemical properties that are difficult to be addressed by linear polymer brushes. On flat surfaces, the ultra-dense and highly compact character of cyclic poly-2-ethyl-2-oxazoline (PEOXA) brushes provide enhanced steric stabilization of the interface, improved biopassivity and highly lubricious behavior, if compared to linear brushes with similar molar mass. The application of random PEOXA-based copolymers with a variable concentration of surface-reactive co-monomers generates mixtures of grafted loops and “tails”. The precise tuning of the relative surface concentration of these two polymer topologies allows shifting of the interfacial properties either towards the ones showed by linear brushes, or near the characteristics of cyclic analogues. An increase in the loops fraction generates an increment of steric repulsion, a concomitant decrease of friction, and an improvement of the antifouling character of the polymer films. All these findings highlight how polymer topological effects, typically observed in bulk or in solution are amplified by adding an additional boundary such as a grafting surface. Their precise tuning translates into materials with unprecedented characteristics and extremely high applicability.