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

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

Unique Dynamical Approach of Fully Wrapping Dendrimer-like Soft Nanoparticles by Lipid Bilayer Membrane

Wrapping dendrimer-like soft nanoparticles by cell membrane is an essential event in their endocytosis in drug and gene delivery, but this process remains poorly elucidated. Using computer simulations and theoretical analysis, we report the detailed dynamics of the process in which a lipid bilayer membrane fully wraps a dendrimer-like soft nanoparticle. By constructing a phase diagram, we firstly demonstrate that there exist three states in the interaction between a dendrimer and a lipid bilayer membrane, <i>i.e.</i>, penetration, penetration and partial wrapping, and full wrapping states. The wrapping process of dendrimer-like nanoparticles is found to take a unique approach where the penetration of the dendrimer into the membrane plays a significant role. The analysis of various energies within the system provides a theoretical justification to the state transition observed from simulations. The findings also support recent experimental results and provide a theoretical explanation for them. We expect that these findings are of immediate interest to the study of the cellular uptake of dendrimer-like soft nanoparticles and can prompt the further application of this class of nanoparticles in nanomedicine

Interplay between Crystallization and Phase Separation in PS‑<i>b</i>‑PMMA/PEO Blends: The Effect of Confinement

Interplay between phase separation and crystallization under confinement for the blends of PEO homopolymers with different molecular weight and PS-<i>b</i>-PMMA block copolymer is studied. Phase structures of the blends are investigated by atomic force microscope (AFM) and theoretically simulated by the dissipative particle dynamics (DPD) method, and a phase diagram describing the phase structure is established. Low molecular weight PEO (PEO2) disperses uniformly in the PMMA block domain and causes a transition from cylinder phase to perforated lamellar phase, while high molecular weight PEO (PEO20) causes expansion of the cylinder domains and formation of disordered domains. Crystallization and melting behavior of the blends are detected by differential scanning calorimetry (DSC). The results show the liquid–liquid phase separation between PEO homopolymer and PMMA block under PS-<i>b</i>-PMMA microphase-separated structure is suppressed due to the hard confinement caused by glassy PS block. As a result, in the blends of PS-<i>b</i>-PMMA/PEO2, PEO2 is unable to crystallize, and in the blends of PS-<i>b</i>-PMMA/PEO20, PEO20 shows a more obvious melting point depression compared with the homopolymer blends of PMMA/PEO20

Interplay between Crystallization and Phase Separation in PS‑<i>b</i>‑PMMA/PEO Blends: The Effect of Confinement

Interplay between phase separation and crystallization under confinement for the blends of PEO homopolymers with different molecular weight and PS-<i>b</i>-PMMA block copolymer is studied. Phase structures of the blends are investigated by atomic force microscope (AFM) and theoretically simulated by the dissipative particle dynamics (DPD) method, and a phase diagram describing the phase structure is established. Low molecular weight PEO (PEO2) disperses uniformly in the PMMA block domain and causes a transition from cylinder phase to perforated lamellar phase, while high molecular weight PEO (PEO20) causes expansion of the cylinder domains and formation of disordered domains. Crystallization and melting behavior of the blends are detected by differential scanning calorimetry (DSC). The results show the liquid–liquid phase separation between PEO homopolymer and PMMA block under PS-<i>b</i>-PMMA microphase-separated structure is suppressed due to the hard confinement caused by glassy PS block. As a result, in the blends of PS-<i>b</i>-PMMA/PEO2, PEO2 is unable to crystallize, and in the blends of PS-<i>b</i>-PMMA/PEO20, PEO20 shows a more obvious melting point depression compared with the homopolymer blends of PMMA/PEO20

Unique Dynamical Approach of Fully Wrapping Dendrimer-like Soft Nanoparticles by Lipid Bilayer Membrane

Wrapping dendrimer-like soft nanoparticles by cell membrane is an essential event in their endocytosis in drug and gene delivery, but this process remains poorly elucidated. Using computer simulations and theoretical analysis, we report the detailed dynamics of the process in which a lipid bilayer membrane fully wraps a dendrimer-like soft nanoparticle. By constructing a phase diagram, we firstly demonstrate that there exist three states in the interaction between a dendrimer and a lipid bilayer membrane, <i>i.e.</i>, penetration, penetration and partial wrapping, and full wrapping states. The wrapping process of dendrimer-like nanoparticles is found to take a unique approach where the penetration of the dendrimer into the membrane plays a significant role. The analysis of various energies within the system provides a theoretical justification to the state transition observed from simulations. The findings also support recent experimental results and provide a theoretical explanation for them. We expect that these findings are of immediate interest to the study of the cellular uptake of dendrimer-like soft nanoparticles and can prompt the further application of this class of nanoparticles in nanomedicine

Interplay between Crystallization and Phase Separation in PS‑<i>b</i>‑PMMA/PEO Blends: The Effect of Confinement

Interplay between phase separation and crystallization under confinement for the blends of PEO homopolymers with different molecular weight and PS-<i>b</i>-PMMA block copolymer is studied. Phase structures of the blends are investigated by atomic force microscope (AFM) and theoretically simulated by the dissipative particle dynamics (DPD) method, and a phase diagram describing the phase structure is established. Low molecular weight PEO (PEO2) disperses uniformly in the PMMA block domain and causes a transition from cylinder phase to perforated lamellar phase, while high molecular weight PEO (PEO20) causes expansion of the cylinder domains and formation of disordered domains. Crystallization and melting behavior of the blends are detected by differential scanning calorimetry (DSC). The results show the liquid–liquid phase separation between PEO homopolymer and PMMA block under PS-<i>b</i>-PMMA microphase-separated structure is suppressed due to the hard confinement caused by glassy PS block. As a result, in the blends of PS-<i>b</i>-PMMA/PEO2, PEO2 is unable to crystallize, and in the blends of PS-<i>b</i>-PMMA/PEO20, PEO20 shows a more obvious melting point depression compared with the homopolymer blends of PMMA/PEO20

Interplay between Crystallization and Phase Separation in PS‑<i>b</i>‑PMMA/PEO Blends: The Effect of Confinement

Interplay between phase separation and crystallization under confinement for the blends of PEO homopolymers with different molecular weight and PS-<i>b</i>-PMMA block copolymer is studied. Phase structures of the blends are investigated by atomic force microscope (AFM) and theoretically simulated by the dissipative particle dynamics (DPD) method, and a phase diagram describing the phase structure is established. Low molecular weight PEO (PEO2) disperses uniformly in the PMMA block domain and causes a transition from cylinder phase to perforated lamellar phase, while high molecular weight PEO (PEO20) causes expansion of the cylinder domains and formation of disordered domains. Crystallization and melting behavior of the blends are detected by differential scanning calorimetry (DSC). The results show the liquid–liquid phase separation between PEO homopolymer and PMMA block under PS-<i>b</i>-PMMA microphase-separated structure is suppressed due to the hard confinement caused by glassy PS block. As a result, in the blends of PS-<i>b</i>-PMMA/PEO2, PEO2 is unable to crystallize, and in the blends of PS-<i>b</i>-PMMA/PEO20, PEO20 shows a more obvious melting point depression compared with the homopolymer blends of PMMA/PEO20

Shearing Janus Nanoparticles Confined in Two-Dimensional Space: Reshaped Cluster Configurations and Defined Assembling Kinetics

The self-assembly of anisotropic nanoparticles (ANPs) possesses a wide array of potential applications in various fields, ranging from nanotechnology to material science. Despite intense research of the thermodynamic self-assembly of ANPs, elucidating their nonequilibrium behaviors under confinement still remains an urgent issue. Here, by performing simulation and theoretical justification, we present for the first time a study of the shear-induced behaviors of Janus spheres (the most elementary ANPs) confined in two-dimensional space. Our results demonstrate that the collective effects of shear and bonding structures can give rise to reshaped cluster configurations, featured by the chiral transition of clusters. Scaling analysis and numerical modeling are performed to quantitatively capture the assembling kinetics of dispersed Janus spheres, thereby suggesting an exotic way to bridge the gap between anisotropic and isotropic particles. The findings highlight confinement and shearing engineering as a versatile strategy to tailor the superstructures formed by ANPs toward unique properties

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

Understanding entropic contributions to ordering transitions is essential for the design of self-assembling systems with tunable hierarchical structures. Herein, we report entropy-mediated precise interfacial organization of Janus nanoparticles in the flexible–semiflexible block copolymers and the resulted optical properties of this heterogeneous material by combining coarse-grained molecular dynamics and a finite difference time domain technique. We find that the stiffness of the semiflexible block can regulate the off-center distribution of symmetric Janus nanoparticles with respect to phase interfaces, featured by a roughly 35% deviation from the interface to the utmost extent. Our simulations reveal how entropic and enthalpic effects in this multiphase media contribute to the self-assembled morphologies and, in particular, can lead to novel chain stiffness-induced entropy effects that can be harnessed to tailor the interfacial organization of Janus nanoparticles in the scaffold of block copolymers. Furthermore, the combination of techniques allows us to determine how changes of the interfacial nanostructures affect the optical properties of the nanocomposite. The findings enable the applications of polymer chain stiffness in precise control over the interfacial assembly of nanoparticles in heterogeneous materials and provide guidelines for facilitating the design of photonic crystals

Receptor-Mediated Endocytosis of Two-Dimensional Nanomaterials Undergoes Flat Vesiculation and Occurs by Revolution and Self-Rotation

Two-dimensional nanomaterials, such as graphene and transitional metal dichalcogenide nanosheets, are promising materials for the development of antimicrobial surfaces and the nanocarriers for intracellular therapy. Understanding cell interaction with these emerging materials is an urgently important issue to promoting their wide applications. Experimental studies suggest that two-dimensional nanomaterials enter cells mainly through receptor-mediated endocytosis. However, the detailed molecular mechanisms and kinetic pathways of such processes remain unknown. Here, we combine computer simulations and theoretical derivation of the energy within the system to show that the receptor-mediated transport of two-dimensional nanomaterials, such as graphene nanosheet across model lipid membrane, experiences a flat vesiculation event governed by the receptor density and membrane tension. The graphene nanosheet is found to undergo revolution relative to the membrane and, particularly, unique self-rotation around its normal during membrane wrapping. We derive explicit expressions for the formation of the flat vesiculation, which reveals that the flat vesiculation event can be fundamentally dominated by a dimensionless parameter and a defined relationship determined by complicated energy contributions. The mechanism offers an essential understanding on the cellular internalization and cytotoxicity of the emerging two-dimensional nanomaterials