Coassembly of Janus Nanoparticles in Asymmetric Diblock Copolymer Scaffolds: Unconventional Entropy Effect and Role of Interfacial Topology

Abstract

The coassembly of Janus nanoparticles and block copolymers offers a unique approach to control the spatial organization of nanoparticles. Herein, using computer simulations and theoretical analysis, we explore the hierarchical structures and underlying mechanisms of the coassembly of symmetric Janus nanoparticles in asymmetric block copolymers. Our simulations constitute the first study clarifying that Janus nanoparticles with two symmetric surface moieties do not take symmetric distribution in the interfaces of asymmetric block copolymers. Rather, they take various but controllable off-center arrangements from the interfaces upon tailoring the molecular architectures of block copolymers and thereby controlling their resulted mesostructural topology. We examine the detailed mechanism of this mesostructural topology-mediated hierarchical assembly and find that the structural asymmetry of the block segments causes unconventional entropy effect at the molecular scale, and the curved interfaces can lead to topology mismatching between Janus nanoparticles and polymer interfaces at the mesoscale. Furthermore, we employ a micromechanical model to demonstrate that the deviation of the Janus nanoparticles from the interface can significantly influence the mechanical properties of the nanocomposites. These findings enrich our understanding on the thermodynamic nature of polymer nanocomposites and may suggest a novel design approach to precisely program the spatial organization of nanoparticles in polymer matrix.

Design and Fabrication of Janus Nanoparticles for Interfacial Distribution in Block Copolymers

“…[31] Janus nanoparticles (JNPs) with two chemically different grafting compartments are especially reported to strongly adsorb and orient to the interface due to their higher interfacial activity and their stronger amphiphilicity compared to homogeneous polymer-grafted NPs. [32][33][34][35][36][37][38][39][40][41] In addition, the orientation and off-center position of JNPs at the interfaces of BCP composites are also reported to be tunable, which is usually governed by an intricate balance of enthalpic and entropic interaction. [38][39][40][41] However, as experimental studies on the incorporation of JNPs in BCP scaffolds are rare, it is difficult to draw a firm conclusion about which of the three types of amphiphilic particles is better for interfacial location just yet.…”

Janus nanoparticles inside polymeric materials: interfacial arrangement toward functional hybrid materials

“…This was done by simply increasing the length of the B block segment (while the length of the A block segment remained the same). 160 For systems presenting a lamellar phase with flat-phase interfaces, Janus NPs tend to move to A domains for the longer Fig. 11 (a-d) Representations of the self-assembly of Janus NPs in AB diblock copolymers with a flexible A block but with B block of various stiffnesses: (a) K a = 0 k B T, (b) K a = 40 k B T, (c) K a = 100 k B T, and (d) K a = 300 k B T. At each K a , the top snapshot shows the self-assembled morphologies where the cyan and pink chains denote blocks A and B, and sites P and Q of every Janus NP are shown in red and yellow, respectively.…”

Chain-Stiffness-Induced Entropy Effects Mediate Interfacial Assembly of Janus Nanoparticles in Block Copolymers: From Interfacial Nanostructures to Optical Responses

“…Additionally, the topology of the fluctuating interface may be another important factor accounting for the reduced wrapping degree, if considering that a topology mismatching will always arise when the symmetry Janus nanoparticle is placed at a curved interface. 55 Kinetic Pathway. To gain an in-depth insight into the formation mechanism of off-center interfacial distribution of Janus nanoparticles in the flexible−semiflexible block copolymers, in Figure 7 we present a typical kinetics pathway where the polymer nanocomposite evolves from an initially random state to the ordered lamellar structure.…”