Polymer loops vs. brushes on surfaces: Adsorption, kinetics, and viscoelastic behavior of α,ω-thiol telechelics on gold

Telechelic thiopolymers were explored towards formation of doubly-bound (polymer loops) vs. singly-bound (polymer brushes) chains on gold substrates. The conformation, adsorption kinetics, and viscoelastic properties of the α,ω-dithiol and monothiol PS telechelics were investigated by means of XPS and QCM-D techniques. The oxidation behavior of the free thiol proved to be important for distinguishing doubly-bound vs. singly-bound chains. The results show a critical dependence of M̄_n on the ability to obtain polymer loops. Comparison with unperturbed dimensions obtained by scaling theory show that the loop is less stretched and occupies more lateral space than the brush. The results are important in demonstrating the different and perhaps superior properties of polymer loops vs. singly-bound polymer brushes. Telechelic thiol polymers are explored towards the formation of doubly-bound polymer chains (polymer loops) vs. singly-bound polymer chains (polymer brushes) on surfaces. The importance of this phenomenon is in controlling the chemisorption of end-functionalized polymers with applications in lubrication, bio-surfaces, and sensing.