Polymer Loops vs. Brushes on Surfaces: Adsorption, Kinetics, and Viscoelastic Behavior of α,ω‐Thiol Telechelics on Gold

Abstract

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 $\overline {M} _{{\rm 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. magnified image

Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach

“…Detailed experimental studies on these materials however have been quite limited due to the lack of efficient approach towards uniform PLBs coating with precisely controlled ring size, molar mass and high grafting density. Up till now, only solution-based physisorption of triblock terpolymer 49 50 51 52 and grafting-to of telechelic polymers 53 54 55 56 have been successfully applied for the synthesis of PLBs on flat surfaces. Yet it is challenging to precisely control final brush structures and grafting density.…”

“…HR S2 p XPS spectra were then employed to investigate the formation of chemical bonds between polymer chain ends and Au substrates to confirm whether these polymer brushes were singly or doubly tethered 54 . The chemical structures of the tethering sites of as-prepared polymer brushes were first examined as shown in the first spectrum of Fig.…”

Loops and Cycles at Surfaces: The Unique Properties of Topological Polymer Brushes

“…Exploiting this last approach, loop PS brushes were formed from carboxylic acid‐bearing PS telechelics reacted to epoxy silane‐based self‐assembled monolayers (SAMs), previously deposited on SIO 2 . Alternatively, epoxy‐terminated bifunctional PS successfully formed loop brushes on carboxylated multiwall carbon nanotubes (COOH‐MWNT), while dithiol‐PS telechelics (HS‐PS‐SH) were applied on Au surfaces to form loop brushes with variable chain‐length …”

Controlled loop and graft formations of water-soluble polymers on SAMs for the design of biomaterials surfaces

“…For both PEG-immobilized I 2nd and polyrotaxane-immobilized II 2nd , smaller values of DD/Df were obtained from substrates with a loop structure (L) than those with a graft structure (G). 20 PEG on a substrate exhibited higher values of DD/Df than polyrotaxane, although exactly the same PEG existed in the polyrotaxane structure in which a number of methylated a-CD molecules are threaded and aligned along the PEG chain to restrict the mobility of PEG. Thus, on substrates in water, it seems that PEG is more flexible and gives more softness to a substrate than polyrotaxane.…”

“…In addition to the above numerous efforts, we are particularly interested in the state of polymers immobilized on a surface, and envisage two types of immobilization modes (loop and graft), [17][18][19][20] as shown in Figure 1. On a surface, one or both terminals of a linear polymeric chain are immobilized though an anchoring group to form a graft or loop structure, and the rest of the surface is covered with a SAM of a conjugate containing an oligo(ethylene glycol).…”