Softness- and Size-Dependent Packing Symmetries of Polymer-Grafted Nanoparticles

Abstract

Achieving ordered arrays of nanoparticles (NPs) with controlled packing symmetry and interparticle spacing is of great importance to design complex metamaterials. Herein, we report softness-and size-dependent self-assembly behavior of polystyrene-grafted Au NPs (Au@PS NPs). We varied the core size of Au NPs from 1.9 to 9.6 nm and the number-average molecular weight (M n ) of thiol-terminated polystyrene from 1.8 to 7.9 kg mol −1 . The optimal packing model based on an "effective softness" parameter λ eff that accounts for close-packed and semidilute brush regimes could predict the effective radius of Au@PS NPs (within ±9%) for a wide range of PS M n , grafting density, and Au core size. With increasing λ eff , the self-assembled Au@PS NP superlattices undergo a symmetry transition from hexagonal close packed (hcp) to body-centered tetragonal (bct) to body-centered cubic (bcc). This work demonstrates the effective softness model as a simple but robust tool for the design of NP superlattices with precisely controlled interparticle distance and packing symmetry, both of which are critical for the development of sophisticated materials through control of nanoscale structure.

Fabrication of Oriented Colloidal Crystals from Capillary Assembly of Polymer‐Tethered Gold Nanoparticles

“…This critical range is close to the reported value (≈1.59-2.31) of Yun et al. [44] More interestingly, the critical L/R range for the formation of bct (≈2. 31-2.85) is also close to the reported effective softness range (≈1.59-2.31), [44] suggesting that L/R could be an effective parameter for the description of the corona softness.…”

“…Previously, the deformation ability or softness of corona can be described by an effective softness parameter λ eff , where λ eff represents the effective softness of the ligands (Figure 6c). According to the report of Stein and Kim, [44] the effective softness parameter value (λ eff ) is calculated as…”

“…Previously, the deformation ability or softness of corona can be described by an effective softness parameter λ eff , where λ eff represents the effective softness of the ligands (Figure 6c). According to the report of Stein and Kim, [ 44 ] the effective softness parameter value (λ eff ) is calculated as where R c is the critical radius for the concentrated polymer brush (CPB) to semidilute polymer brush (SDPB) transition, L eff is the stretched length of polymer chains in the SDPB regime, and N SDPB is the number of monomers per chain in the SDPB regime. R c is calculated by the theoretical model to predict the CPB to SDPB crossover where Σ is the grafting density, R is the core radius, l 0 is the monomer length, and v = 0.5 − χ is the excluded volume parameter, where χ is the Flory−Huggins parameter.…”

Fluorescence Switchable Block Copolymer Particles with Doubly Alternate‐Layered Nanoparticle Arrays

“…Preparation of Au NPs Grafted with PSSH (Au@PS): PSSH ligands were grafted onto the surfaces of Au NPs following a ligand-exchange process. [28] In a typical process, the as-synthesized oleylamine-capped Au NPs were dispersed in THF at a NP concentration of 5 mg mL −1 . A PSSH ligand solution was prepared by dissolving PSSH in THF at a concentration of 10 mg mL −1 .…”

Kinetically Controlled Self-Assembly of Binary Polymer-Grafted Nanocrystals into Ordered Superstructures via Solvent Vapor Annealing

“…2,[7][8][9][10][11] Grafting polymers onto pre-synthesized nanocrystals (NCs) introduces new energetic contributions arising from the conformational entropy and interaction enthalpy of polymer chains, offering a vast parameter space for nanocomposite design. [12][13][14][15][16][17][18] While diverse NC and PGNC superstructures have been synthesized by evaporationdriven self-assembly, 8,[19][20][21][22][23][24][25][26][27][28] it remains very challenging to study the kinetic pathways of crystallization especially for multicomponent systems. The main challenge lies in the difficulty of realspace observation of structural intermediates during disorderto-order transitions.…”