Abstract
Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional ‘grafting-to' and ‘grafting-from' methods, and is promising for tailored synthesis of polymer brushes.
Highlights
Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades
We demonstrated that surface-functionalized 2D polymer single crystals (PSCs) can be considered as free-standing ‘self-assembled monolayers’— they can collect nanoparticles, and the resultant hybrid materials can be used in applications such as nanoparticle asymmetric functionalization, nanomotors, surface-enhanced Raman spectroscopy and catalysis supports[23,24,25,26,27,28]
Hydroxyl-terminated PCL (PCL-OH) was first synthesized via ring-opening polymerization using tetraethylene glycol monomethyl ether as the initiator followed by chain end functionalization using 3-(triethoxysilyl)propyl isocyanate
Summary
Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. We disclose an approach, which is fundamentally different from the previously reported methods, to synthesize polymer brushes with controlled structure and high grafting density on flat surfaces. In this approach, we first pre-assemble end-functionalized polymers into two-dimensional (2D) polymer single crystals (PSCs) using controlled crystallization. We demonstrated that surface-functionalized 2D PSCs can be considered as free-standing ‘self-assembled monolayers’— they can collect nanoparticles, and the resultant hybrid materials can be used in applications such as nanoparticle asymmetric functionalization, nanomotors, surface-enhanced Raman spectroscopy and catalysis supports[23,24,25,26,27,28] These surfacefunctionalized 2D single crystals provide a unique opportunity for the synthesis of well-defined polymer brushes. Compared with previously reported conventional brush synthesis approaches, our strategy combines the advantages of both grafting-to and grafting-from methods, leading to polymer brushes with well-controlled structures and high grafting density
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