Block Copolymer Mimetic Self-Assembly of Inorganic Nanoparticles

Abstract

Emerging strategies for assembling inorganic nanoparticles into ensembles with multiscale organization are establishing a new paradigm for the synthesis of devices and functional materials with applications ranging from drug delivery to photonics. In this work, the solution self-assembly of amphiphilic ionic block copolymers into morphologically tunable aggregates provides the inspiration and design strategy for nanoparticle building blocks with the essential chemical and conformational features of ionic block copolymer chains in aqueous media. We produce inorganic nanoparticles with surface-tethered mixed brushes of hydrophobic and chargeable hydrophilic chains which self-assemble in polar solvent mixtures into unprecedented hierarchical superstructures analogous to known ionic block copolymer aggregates but with complex organizations of nanoparticles in three dimensions. Electrostatic repulsion between hydrophilic chains forces nonequilibrium pathways to variable kinetic structures with internal lamellar organization of nanoparticles; however, decreasing electrostatic interactions through salt or acid addition allows tunable equilibrium assemblies, including supermicelles and bilayer vesicles of nanoparticles, to be formed. The application of ionic block copolymer assembly principles and mechanisms opens a new chemical toolbox for the organization of nanoparticles into functional assemblies.

Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

“…3): BCP-tethered HNPs have been used by multiple researchers to create complex structures such as tubules and vesicles with walls built out of HNPs, [52] as well as lamellae and "segmented worms." [53] Jayaraman and Schweizer used a modified version of the polymer reference interaction site model to investigate structure formation for particles with very low graft densities; 1, 2, 4, and 6 polymers per particle. [54][55][56] Systems with 1 and 2 chains per particle are analogous to di-block and tri-block copolymers, with the nanoparticle forming one of the blocks, and results of these simulations, as well as computational studies by Iacovella, Glotzer, and others show the same micellar, lamellar, and interpenetrating gyroid structures seen in copolymer systems (Fig.…”

Amphiphilic Quantum Dots with Asymmetric, Mixed Polymer Brush Layers: From Single Core-Shell Nanoparticles to Salt-Induced Vesicle Formation

“…Since GPC results before and after hydrolysis suggest that aggregation numbers for PS/PMMA-CdS and PS/PMAA-CdS should be the same, this agreement between SLS and TEM results supports the conclusion that each core-shell particle ( Figure 4) arises from intraparticle chain rearrangements of a single PS/PMAA-CdS unit upon water addition. We have previously shown that ABNPs exhibit salt-dependent self-assembly characteristics due to the charging of PAA chains in water [17]. Therefore, we investigated the effect of adding salt on the behaviour of PS/PMAA-CdS upon dropwise water addition.…”

“…When the salt ratio was increased to RNaCl = 3.0, vesicles were also formed ( Figure 5C), although with slightly thicker walls (t = 35 ± 2 nm) than those formed at the lower salt ratio. We have previously shown that ABNPs exhibit salt-dependent self-assembly characteristics due to the charging of PAA chains in water [17]. Therefore, we investigated the effect of adding salt on the behaviour of PS/PMAA-CdS upon dropwise water addition.…”

“…Subsequent crosslinking of the micelle cores and hydrolysis of PMMA chains to poly(methacrylic acid) (PMAA) formed amphiphilic brush nanoparticles (ABNPs) with QD cores and mixed brush layers consisting of equal numbers of hydrophobic PS and hydrophilic, ionizable PMAA chains [17]. The ABNPs underwent self-assembly in tetrahydrofuran (THF)/water mixtures to generate spherical supermicelles,…”

“…The ABNPs underwent self-assembly in tetrahydrofuran (THF)/water mixtures to generate spherical supermicelles, vesicles, and segmented wormlike aggregates depending on the chemical conditions, including salt content [17].…”