Postpolymerization Modification of Multicyclic Polymers via the Thiol–ene Click Reaction for Applications in Surface Polymer Grafting

Although cyclic polymer brushes are expected to exhibit unique surface characteristics due to their chain-end-free topology, simple and versatile synthetic approaches remain limited. Our group previously developed a one-step synthetic strategy for multicyclic polymers via cyclopolymerization based on ring-opening metathesis polymerization. By leveraging the internal double bonds on multicyclic polymers, the current study demonstrates that the thiol–ene reaction efficiently introduces anchoring groups for surface grafting. Specifically, multicyclic polymers bearing poly(dimethylsiloxane) (PDMS), polystyrene, and poly(ethylene glycol) backbones are functionalized with trimethoxysilyl, phosphoryl, and carboxyl groups via thiol–ene reactions. These functionalized multicyclic polymers are grafted onto hydroxylated substrate surfaces to form high-density polymer brushes on various substrates. For instance, multicyclic PDMS forms high-density polymer brushes on silicon substrates with tether densities of >5. Furthermore, blending linear polystyrene with multicyclic polystyrene-bearing anchoring groups results in strong adhesion to the glass substrate, which is attributed to chemical bonding of the anchoring groups to the surface and entanglement between the linear chains and the cyclic units. This straightforward strategy for preparing multicyclic polymer brushes provides a versatile platform for the development of polymer coatings with unique interfacial properties.