High-Density PEO-b-DNA Brushes on Polymer Particles for Colloidal Superstructures

Abstract

We demonstrate a method to create highdensity DNA coatings on colloidal particles that can be used for DNA-mediated self-assembly of single-and multiplecomponent colloidal crystals. First, we modify an amphiphilic diblock copolymer consisting of a hydrophobic polystyrene (PS) block and a hydrophilic poly(ethylene oxide) (PEO) block with azide functional groups at the end (poly(ethylene oxide)-N 3 ). Then, we introduce the diblock copolymers into an aqueous suspension of colloidal polymer particles swollen with a solvent. The hydrophobic PS anchoring block is incorporated into the swollen polymer spheres and physically trapped when the solvent is removed, resulting in a dense PEO polymer brush with azide functional end groups. Finally, singlestranded DNA strands with sticky ends are attached to the azide groups using strain-promoted azide−alkyne cycloaddition (SPAAC, a copper-free click chemistry). This procedure results in a high areal coverage of up to 225 000 DNA strands on 1-μmdiameter particles. The ssDNA-coated particles with sticky ends can readily form either face-centered-cubic (fcc) or cesium chloride (CsCl) crystal structures when annealed just below the melting temperature of the DNA-coated particles.

Compressible colloidal clusters from Pickering emulsions and their DNA functionalization

“…PS-b-PEO-N 3 was prepared using a previously reported method. 1 Briefly, we activated the hydroxyl groups of PS-b-PEO and reacted with NaN 3 to make azide functional end groups. Then, we incorporated the PS-b-PEO-N 3 into PS particles using the swelling/deswelling method.…”

Using DNA strand displacement to control interactions in DNA-grafted colloids

“…[34][35][36] We also foresee no obstacles to integrating strand-displacement reactions into the emulsion systems with the mobile DNA strands demonstrated by Brujic and coworkers. 37,38 8 Methods and materials…”

Chain End‐Functionalized Polymer Brushes with Switchable Fluorescence Response

“…These include converting alkyl bromide end groups into amines before reacting with isothiocyanate‐functionalized dye as well as nitroxide radical exchange during polymerization . A straightforward alternative to these synthetic routes could be “click chemistry,” which was previously used to modify chain‐ends of polymer brushes with, for example, recognition elements, DNA, and polyethylene glycol (PEG) …”

“…[1][2][3] For example, fluorescent dye-labeled polymers have been used to study polymer chain dynamics in solution, [4][5][6] local glass transition temperature of block copolymers, [7] and structures of block copolymer micelles. [8] Localization of the dye at the chain-end of the polymer backbone can offer advantages including minimally affected intrinsic polymer properties (such as solubility and conformation), minimum self-quenching between closely located dyes, and the binding possibility of recognition molecules in chain-ends of polymer brushes with, for example, recognition elements, [34][35][36][37] DNA, [38] and polyethylene glycol (PEG). [39] Here we present switchable fluorescent response of chain end dye-functionalized poly(methyl methacrylate) (PMMA) polymer brushes utilizing co-solvency effect displayed by PMMA in alcohol-water mixtures.…”