Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]- Modified Patchy Particles Farah Benyettou, † Xiaolong Zheng, ‡ Elizabeth Elacqua, ‡ Yu Wang, ‡ Parastoo Dalvand, § Zouhair Asfari, ∥ John-Carl Olsen, ⊥ Dong Suk Han, # Na’il Saleh, ∇ Mourad Elhabiri, § Marcus Weck,* ,‡ and Ali Trabolsi* ,† † New York University Abu Dhabi, Abu Dhabi, United Arab Emirates ‡ Molecular Design Institute and Department of Chemistry, New York University, New York, New York 10003, United States § Laboratoire de Chimie Bioorganique et Me ́ dicinale, UMR 7509 CNRS, Universite ́ de Strasbourg, ECPM, Strasbourg, France ∥ Laboratoire d’Inge ́ nierie Mole ́ culaire Applique ́ ea ̀ l’Analyse, IPHC, UMR 7178 CNRS, Universite ́ de Strasbourg, ECPM, 25 rue Becquerel, 67200 Strasbourg, France ⊥ School of Sciences, Indiana University Kokomo, Kokomo, Indiana 46904, United States # Chemical Engineering Program, Texas A&M University at Qatar, Education City, Doha, Qatar ∇ College of Science, Department of Chemistry, United Arab Emirates University, Al-Ain, United Arab Emirates * S Supporting Information ABSTRACT: Sulfonated surface patches of poly(styrene)- based colloidal particles (CPs) were functionalized with cucurbit[7]uril (CB[7]). The macrocycles served as recognition units for diphenyl viologen (DPV 2+ ), a rigid bridging ligand. The addition of DPV 2+ to aqueous suspensions of the particles triggered the self-assembly of short linear and branched chainlike structures. The self-assembly mechanism is based on hydrophobic/ion-charge interactions that are established between DPV 2+ and surface-adsorbed CB[7]. DPV 2+ guides the self-assembly of the CPs by forming a ternary DPV 2+ ⊂(CB- [7]) 2 complex in which the two CB[7] macrocycles are attached to two different particles. Viologen-driven particle assembly was found to be both directional and reversible. Whereas sodium chloride triggers irreversible particle dis- assembly, the one-electron reduction of DPV 2+ with sodium dithionite causes disassembly that can be reversed via air oxidation. Thus, this bottom-up synthetic supramolecular approach allowed for the reversible formation and directional alignment of a 2D colloidal material. ■ INTRODUCTION The self-assembly of anisotropic particles into well-defined supracolloidal structures 1−3 is of widespread interest owing to potential applications in plasmonics, 4,5 photonics, 6 catalysis, 7 and drug delivery. 8 Recent efforts have led to the fabrication of anisotropic particles, including ellipsoids, 9−11 rods, 12 Janus particles, 13 dimpled particles, 14,15 and patchy particles. 2,12,16−20 Additionally, strategies have been developed that rely on short- range attractions to direct their self-assembly. 21−23 Patchy particles, in particular, can be fabricated with site-specific chemical activity on their surface, endowing such particles with valency and directionality. These features allow the particles to assemble into more complex or higher-ordered structures that are less accessible through spherical or other simply shaped particles. For example, a Kagome lattice has been fabricated from triblock Janus particles (dipatch particles) driven by hydrophobic interactions between patches. Previously, we reported a general method to fabricate a vast collection of particle symmetries, with chemically distinct surface patches that imitate hybridized atomic orbitals. 16 Patch−patch interactions were realized by DNA hybridization or metal coordination, 16,23 allowing the particles to assemble into colloidal molecules and macromolecules that are analogous to organic molecules using atomic bonding. Although these results demonstrate the feasibility of using patchy particles to construct sophisticated colloidal superstructures, the binding schemes for guiding particle assembly into more complex and/ or crystalline lattices are limited in approach and are not generally applicable to different systems. For example, DNA hybridization or hydrophobic interactions are designed to work under aqueous media, and temperature is used to control the Received: April 20, 2016 Revised: June 17, 2016 Published: June 21, 2016 Article pubs.acs.org/Langmuir © 2016 American Chemical Society 7144 DOI: 10.1021/acs.langmuir.6b01433 Langmuir 2016, 32, 7144−7150