Supramolecular Polymer Brushes

Abstract

Polymer brushes are thin polymer films that consist of densely grafted, chain-end tethered polymers. These thin polymer films can be produced either by anchoring presynthesized chain-end functional polymers to the surface of interest (“grafting to”), or by using appropriately modified surfaces to facilitate growth of polymer chains from the substrate (“grafting from”). The vast majority of polymer brushes that have been prepared and studied so far involved chain-end tethered polymer assemblies that are anchored to the surface via covalent bonds. In contrast, the use of noncovalent interactions to prepare chain-end tethered polymer thin films is much less explored. Anchoring or growing polymer chains using noncovalent interactions results in supramolecular polymer brushes. Supramolecular polymer brushes may possess unique chain dynamics as opposed to their covalently tethered counterparts, which could provide avenues to, for example, renewable or (self-)healable surface coatings. This Perspective article provides an overview of the various approaches that have been used so far to prepare supramolecular polymer brushes. After presenting an overview of the various approaches that have been used to prepare supramolecular brushes via the “grafting to” strategy, examples will be presented of strategies that have been successfully applied to produce supramolecular polymer brushes via “grafting from” methods.

Supramolecular Polymer Brushes Grown by Surface‐Initiated Atom Transfer Radical Polymerization from Cucurbit[7]uril‐based Non‐Covalent Initiators

“…Careful control of these parameters will allow to tune the responsiveness/reversibility of these supramolecular brushes. The ability to produce supramolecular polymer brushes via surface‐initiated polymerization provides further opportunities, for example, towards lubrication surfaces capable of self‐repair [20,42] …”

“…The ability to produce supramolecular polymer brushes via surface-initiated polymerization provides further opportunities, for example, towards lubrication surfaces capable of self-repair. [20,42]…”

“…While there have been some efforts to explore supramolecular approaches to chain end tether polymer grafts to solid surfaces, both via the grafting-from strategy that is presented here, as well as via grafting-onto approaches, [20] comparably little is known about the thermodynamics and kinetics of these interactions at solid surfaces and the stability of the resulting supramolecular polymer brushes. In a first attempt to obtain insight in the formation of surface-bound Ada@CB [7] host-guest complexes, a silicon substrate presenting surface-anchored CB [7] moieties was presented with a series of Ada-Flu solutions covering a range of concentrations from 0.23 to 7.5 μM.…”

“…So far, only few examples have been reported of supramolecular polymer brushes that were grown via surface-initiated polymerization from substrates, which present initiators anchored via non-covalent interactions. [20] In one example, pyrene-functionalized initiators were used to graft brushes from graphene. [21] In another study, which also harnessed π-π interactions, supramolecular polymer brushes were grown from hydroxyl-functionalized selfassembled monolayers on silicon substrates that presented microcontact printed pyrene-based initiators.…”

“…The use of non‐covalent chemistries to anchor polymerization initiators or CTAs to the substrate, and subsequently grow polymer brushes, in contrast, is much less explored. So far, only few examples have been reported of supramolecular polymer brushes that were grown via surface‐initiated polymerization from substrates, which present initiators anchored via non‐covalent interactions [20] . In one example, pyrene‐functionalized initiators were used to graft brushes from graphene [21] .…”