Block copolymer–nanoparticle composites: Structure, functional properties, and processing

Nanoparticle assembly by transient topography induced by applying soft lithography to block copolymer films

We present a simple approach for patterning metal nanoparticles into periodic superstructures on flat films spanning centimeter-square areas. Our approach is based on capillary force lithography, a soft lithography method that is used to impart topography to molten polymer films, and applies it to block copolymer films to obtain substrates featuring both topographic and chemical contrasts that can serve as templates for the selective deposition of nanoparticles. Here we show that flattening the films by exposure to solvent vapour prior to nanoparticle deposition not only retains chemical heterogeneity but also provides access to unique hierarchically-organized nanoparticle superstructures that are unattainable by other methods. Such structures could be useful for optical, sensor, and catalytic applications.

Multilaminate Energy Storage Films from Entropy-Driven Self-Assembled Supramolecular Nanocomposites

Composite materials comprising polymers and inorganic nanoparticles (NPs) are promising for energy storage applications, though challenges in controlling NP dispersion often result in performance bottlenecks. Realizing nanocomposites with controlled NP locations and distributions within polymer microdomains is highly desirable for improving energy storage capabilities but is a persistent challenge, impeding the in-depth understanding of the structure-performance relationship. In this study, a facile entropy-driven self-assembly approach is employed to fabricate block copolymer-based supramolecular nanocomposite films with highly ordered lamellar structures, which are then used in electrostatic film capacitors. The oriented interfacial barriers and well-distributed inorganic NPs within the self-assembled multilaminate nanocomposites effectively suppress leakage current and mitigate the risk of breakdown, showing superior dielectric strength compared to their disordered counterparts. Consequently, the lamellar nanocomposite films with optimized composition exhibit high energy efficiency (>90% at 650 MV m-1), along with remarkable energy density and power density. Moreover, finite element simulations and statistical modeling have provided theoretical insights into the impact of the lamellar structure on electrical conduction, electric field distribution, and electrical tree propagation. This work marks a significant advancement in the design of organic-inorganic hybrids for energy storage, establishing a well-defined correlation between microstructure and performance.

Stimuli-responsive nanoparticle self-assembly at complex fluid interfaces: a new insight into dynamic surface chemistry

The self-assembly of core/shell nanoparticles (NPs) at fluid interfaces is a rapidly evolving area with tremendous potential in various fields, including biomedicine, display devices, catalysts, and sensors. This review provides an in-depth exploration of the current state-of-the-art in the programmed design of stimuli-responsive NP assemblies, with a specific focus on inorganic core/organic shell NPs below 100 nm for their responsive adsorption properties at fluid and polymer interfaces. The interface properties, such as ligands, charge, and surface chemistry, play a significant role in dictating the forces and energies governing both NP-NP and NP-hosting matrix interactions. We highlight the fundamental principles governing the reversible surface chemistry of NPs and present detailed experimental examples in the following three key aspects of stimuli-responsive NP assembly: (i) stimuli-driven assembly of NPs at the air/liquid interface, (ii) reversible NP assembly at the liquid/liquid interface, including films and Pickering emulsions, and (iii) hybrid NP assemblies at the polymer/polymer and polymer/water interfaces that exhibit stimuli-responsive behaviors. Finally, we address current challenges in existing approaches and offer a new perspective on the advances in this field.

Nanoscale polymer discs, toroids and platelets: a survey of their syntheses and potential applications

Polymer self-assembly has become a reliable and versatile workhorse to produce polymeric nanomaterials. With appropriate polymer design and monomer selection, polymers can assemble into shapes and morphologies beyond well-studied spherical and cylindrical micellar structures. Steadfast access to anisotropic polymer nanoparticles has meant that the fabrication and application of 2D soft matter has received increasing attention in recent years. In this review, we focus on nanoscale polymer discs, toroids, and platelets: three morphologies that are often interrelated and made from similar starting materials or common intermediates. For each morphology, we illustrate design rules, and group and discuss commonly used self-assembly strategies. We further highlight polymer compositions, fundamental principles and self-assembly conditions that enable precision in bottom-up fabrication strategies. Finally, we summarise potential applications of such nanomaterials, especially in the context of biomedical research and template chemistry and elaborate on future endeavours in this space.

Rationally designed block copolymer-based nanoarchitectures: An emerging paradigm for effective drug delivery

Various polymeric materials have been investigated to produce unique modes of delivery for drug modules to achieve either temporal or spatial control of bioactives delivery. However, after intravenous administration, phagocytic cells quickly remove these nanostructures from the systemic circulation via the reticuloendothelial system (RES). To overcome these concerns, ecofriendly block copolymers are increasingly being investigated as innovative carriers for the delivery of bioactives. In this review, we discuss the design, fabrication techniques, and recent advances in the development of block copolymers and their applications as drug carrier systems to improve the physicochemical and pharmacological attributes of bioactives.

Dynamic Processes and Mechanical Properties of Lipid-Nanoparticle Mixtures

In this study, we investigate the dynamic processes and mechanical properties of lipid nanoparticle mixtures in a melt via dissipation particle dynamic simulation. By investigating the distribution of nanoparticles in lamellar and hexagonal lipid matrices in equilibrium state and dynamic processes, we observe that the morphology of such composites depends not only on the geometric features of the lipid matrix but also on the concentration of nanoparticles. The dynamic processes are also demonstrated by calculating the average radius of gyration, which indicates the isotropic conformation of lipid molecules in the x-y plane and that the lipid chains are stretched in the z direction with the addition of nanoparticles. Meanwhile, we predict the mechanical properties of lipid-nanoparticle mixtures in lamellar structures by analyzing the interfacial tensions. Results show that the interfacial tension decreased with the increase in nanoparticle concentration. These results provide molecular-level information for the rational and a priori design of new lipid nanocomposites with ad hoc tailored properties.

Amphiphilic Block Copolymers: Their Structures, and Self-Assembly to Polymeric Micelles and Polymersomes as Drug Delivery Vehicles

Self-assembly of amphiphilic block copolymers display a multiplicity of nanoscale periodic patterns proposed as a dominant tool for the 'bottom-up' fabrication of nanomaterials with different levels of ordering. The present review article focuses on the recent updates to the self-association of amphiphilic block copolymers in aqueous media into varied core-shell morphologies. We briefly describe the block copolymers, their types, microdomain formation in bulk and micellization in selective solvents. We also discuss the characteristic features of block copolymers nanoaggregates viz., polymer micelles (PMs) and polymersomes. Amphiphilic block copolymers (with a variety of hydrophobic blocks and hydrophilic blocks; often polyethylene oxide) self-assemble in water to micelles/niosomes similar to conventional nonionic surfactants with high drug loading capacity. Double hydrophilic block copolymers (DHBCs) made of neutral block-neutral block or neutral block-charged block can transform one block to become hydrophobic under the influence of a stimulus (physical/chemical/biological), and thus induced amphiphilicity and display self-assembly are discussed. Different kinds of polymer micelles (viz. shell and core-cross-linked, core-shell-corona, schizophrenic, crew cut, Janus) are presented in detail. Updates on polymerization-induced self-assembly (PISA) and crystallization-driven self-assembly (CDSA) are also provided. Polyion complexes (PICs) and polyion complex micelles (PICMs) are discussed. Applications of these block copolymeric micelles and polymersomes as nanocarriers in drug delivery systems are described.

Progress in the self-assembly of organic/inorganic polyhedral oligomeric silsesquioxane (POSS) hybrids

This Review describes recent progress in the self-assembly of organic/inorganic POSS hybrids derived from mono-, di-, and multi-functionalized POSS cages. We highlight the self-assembled structures and physical properties of giant surfactants and chain-end- and side-chain-type hybrids derived from mono-functionalized POSS cages; main-chain-type hybrids derived from di-functionalized POSS cages; and star-shaped hybrids derived from multi-functionalized POSS cages; with various polymeric attachments, including polystyrene, poly(methyl methacrylate), phenolic, PVPh, and polypeptides.

Symmetry-Breaking and Self-Sorting in Block Copolymer-Based Multicomponent Nanocomposites

Co-assembly of inorganic nanoparticles (NPs) and nanostructured polymer matrix represents an intricate interplay of enthalpic or entropic forces. Particle size largely affects the phase behavior of the nanocomposite. Theoretical studies indicate that new morphologies would emerge when the particles become comparable to the soft matrix's size, but this has rarely been supported experimentally. By designing a multicomponent blend composed of NPs, block copolymer-based supramolecules, and small molecules, a 3-D ordered lattice beyond the native BCP's morphology was recently reported when the particle is larger than the microdomain of BCP. The blend can accommodate various formulation variables. In this paper, when the particle size equals the microdomain size, a symmetry-broken phase appears in a narrow range of particle sizes and compositions, which we named the "train track" structure. In this phase, the NPs aligned into a 3-D hexagonal lattice and packed asymmetrically along the c axis, making the projection of the ac and the bc plane resemble train tracks. Computational studies show that the broken symmetry reduces the polymer chain deformation and stabilizes the metastable hexagonally perforated lamellar morphology. Given the mobility of the multicomponent blend, the system shows a self-sorting behavior: segregating into two macroscopic phases with different nanostructures based on only a few nanometers NP size differences. Smaller NPs form "train track" morphology, while larger NPs form a "simple hexagon" structure, where the NPs take a symmetric hexagonal arrangement. Detailed structural evolution and simulation studies confirm the systematic-wide cooperativity across different components, indicating the strong self-regulation of the multicomponent system.

Nanoparticle-induced morphological transformation in block copolymer-based nanocomposites

By controlling the chemical composition and the spatial organization of nanoparticles, hybrid nanocomposites incorporating ordered arrangements of nanoparticles could be endowed with exotic physical and chemical properties to fulfill demands in advanced electronics or energy-harvesting devices. However, a simple method to fabricate hybrid nanocomposites with precise control of nanoparticle distribution is still challenging. We demonstrate that block copolymer-based nanocomposites containing well-ordered nanoparticles with various morphologies can be readily obtained by adjusting the nanoparticle concentration. Moreover, the structural evolution of nanocomposite thin films as a function of nanoparticle loading is unveiled using grazing-incidence transmission small-angle X-ray scattering and atomic force microscopy. The morphological transformation proceeds through a phase transition from perforated lamellae to in-plane cylinder layout, followed by structural changes. The successful achievement of a variety of morphologies represents an effective and straightforward approach to producing functional hybrid nanocomposites for potential applications in various functional devices.

Solvent-assisted self-assembly of block copolymer thin films

Solvent-assisted block copolymer self-assembly is a compelling method for processing and advancing practical applications of these materials due to the exceptional level of the control of BCP morphology and significant acceleration of ordering kinetics. Despite substantial experimental and theoretical efforts devoted to understanding of solvent-assisted BCP film ordering, the development of a universal BCP patterning protocol remains elusive; possibly due to a multitude of factors which dictate the self-assembly scenario. The aim of this review is to aggregate both seminal reports and the latest progress in solvent-assisted directed self-assembly and to provide the reader with theoretical background, including the outline of BCP ordering thermodynamics and kinetics phenomena. We also indicate significant BCP research areas and emerging high-tech applications where solvent-assisted processing might play a dominant role.

Design of composite nanosupports and applications thereof in enzyme immobilization: A review

Enzyme immobilization techniques have developed dramatically over the past several decades. Support materials are key in shaping the function of a specific immobilized enzyme. Although they have large specific surface areas and functional active sites, single-component nanomaterials and their surface chemical modification derivatives struggle to meet increasing demand. Thus, composite materials, compounds of two or more materials, have been developed and applied in efficient immobilization through advances in materials science. More methods have been developed and employed to design composite nanomaterials in recent years. These novel composite nanomaterials often show superior physical, chemical, and biological performance as supports in enzyme immobilization, among other applications. In this review, immobilization techniques and their supports are stated first and methods to design and fabricate composite nanomaterials as nanosupports are also shown in the following section. Applications of composite nanosupports in laccase immobilization are discussed as models in the later sections of the paper. This review is intended to help readers gain insight into the design principles of composite nanomaterials for immobilization supports.

Hybrid Time-Dependent Ginzburg–Landau Simulations of Block Copolymer Nanocomposites: Nanoparticle Anisotropy

Block copolymer melts are perfect candidates to template the position of colloidal nanoparticles in the nanoscale, on top of their well-known suitability for lithography applications. This is due to their ability to self-assemble into periodic ordered structures, in which nanoparticles can segregate depending on the polymer–particle interactions, size and shape. The resulting coassembled structure can be highly ordered as a combination of both the polymeric and colloidal properties. The time-dependent Ginzburg–Landau model for the block copolymer was combined with Brownian dynamics for nanoparticles, resulting in an efficient mesoscopic model to study the complex behaviour of block copolymer nanocomposites. This review covers recent developments of the time-dependent Ginzburg–Landau/Brownian dynamics scheme. This includes efforts to parallelise the numerical scheme and applications of the model. The validity of the model is studied by comparing simulation and experimental results for isotropic nanoparticles. Extensions to simulate nonspherical and inhomogeneous nanoparticles are discussed and simulation results are discussed. The time-dependent Ginzburg–Landau/Brownian dynamics scheme is shown to be a flexible method which can account for the relatively large system sizes required to study block copolymer nanocomposite systems, while being easily extensible to simulate nonspherical nanoparticles.

Phase Behaviors of ABA Star Polymer and Nanoparticles Confined in a Sphere with Soft Inner Surface

The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere were focused. Two cases are considered: one is that the nanoparticles interact with the B blocks and the other is that the nanoparticles preferentially wet the B blocks. Under the two conditions, through changing the block ratio of the ABA star polymer, the concentration and radius of the nanoparticles, the phase behaviors of the mixtures confined the soft sphere are studied systematically. With increasing the concentration of nanoparticles, the entropy and the steric repulsive interaction of nanoparticles, and the nanoparticle density distributions along the perpendicular line through the center of sphere are plotted. The phase diagram is also constructed to analyze the effects of the nanoparticle volume fraction and radius on morphologies of ABA star polymers, and to study the effect of confinement on the phase behaviors. The results in this work provide a useful reference for controlling the ordered structures in experiment, which is an effective way to fabricate the newly multifunctional materials.

Fabrication of Nanodevices Through Block Copolymer Self-Assembly

Block copolymer (BCP) self-assembly, as a novel bottom-up patterning technique, has received increasing attention in the manufacture of nanodevices because of its significant advantages of high resolution, high throughput, low cost, and simple processing. BCP self-assembly provides a very powerful approach to constructing diverse nanoscale templates and patterns that meet large-scale manufacturing practices. For the past 20 years, the self-assembly of BCPs has been extensively employed to produce a range of nanodevices, such as nonvolatile memory, bit-patterned media (BPM), fin field-effect transistors (FinFETs), photonic nanodevices, solar cells, biological and chemical sensors, and ultrafiltration membranes, providing a variety of configurations for high-density integration and cost-efficient manufacturing. In this review, we summarize the recent progress in the fabrication of nanodevices using the templates of BCP self-assembly, and present current challenges and future opportunities.

Vertical Cylinder-to-Lamella Transition in Thin Block Copolymer Films Induced by In-Plane Electric Field

Morphological transition between hexagonal and lamellar patterns in thin polystyrene-block-poly(4-vinyl pyridine) films simultaneously exposed to a strong in-plane electric field and saturated solvent vapor is studied with atomic force and scanning electron microscopy. In these conditions, standing cylinders made of 4-vinyl pyridine blocks arrange into threads up to tens of microns long along the field direction and then partially merge into standing lamellas. In the course of rearrangement, the copolymer remains strongly segregated, with the minor component domains keeping connectivity between the film surfaces. The ordering tendency becomes more pronounced if the cylinders are doped with Au nanorods, which can increase their dielectric permittivity. Non-selective chloroform vapor works particularly well, though it causes partial etching of the indium tin oxide cathode. On the contrary, 1,4-dioxane vapor selective to polystyrene matrix does not allow for any morphological changes.

Synthesis of Poly(ionic Liquid)s-block-poly(methyl Methacrylate) Copolymer-Grafted Silica Particle Brushes with Enhanced CO2 Permeability and Mechanical Performance

Poly(ionic liquid) (PIL)-based block copolymers are of particular interest as they combine the specific properties of PILs with the self-assembling behaviors of block copolymers, broadening the range of potential applications for PIL-based materials. In this work, three particle brushes: SiO₂-g-poly(methyl methacrylate) (PMMA), SiO₂-g-PIL, and SiO₂-g-PMMA-b-PIL were prepared through surface-initiated atom transfer radical polymerization. Unlike the homogeneous homopolymer particle brushes, the block copolymer particle brush SiO₂-g-PMMA-b-PIL exhibited a bimodal chain architecture and unique phase-separated morphology, which were confirmed by size-exclusion chromatography and transmission electron microscopy. In addition, the influence of the introduction of the PMMA segment on the gas separation and mechanical performance of the PIL-containing block copolymer particle brushes were investigated. A significant improvement of Young's modulus was observed in the SiO₂-g-PMMA-b-PIL compared to the SiO₂-g-PIL bulk films; meanwhile, their gas separation performances (CO₂ permeability and CO₂/N₂ selectivity) were the same, which demonstrates the possibility of improving the mechanical properties of PIL-based particle brushes without compromising their gas separation performance.

Dispersion of Few-Layer Black Phosphorus in Binary Polymer Blend and Block Copolymer Matrices

Exfoliated black phosphorus (bP) embedded into a polymer is preserved from oxidation, is stable to air, light, and humidity, and can be further processed into devices without degrading its properties. Most of the examples of exfoliated bP/polymer composites involve a single polymer matrix. Herein, we report the preparation of biphasic polystyrene/poly(methyl methacrylate) (50/50 wt.%) composites containing few-layer black phosphorus (fl-bP) (0.6–1 wt.%) produced by sonicated-assisted liquid-phase exfoliation. Micro-Raman spectroscopy confirmed the integrity of fl-bP, while scanning electron microscopy evidenced the influence of fl-bP into the coalescence of polymeric phases. Furthermore, the topography of thin films analyzed by atomic force microscopy confirmed the effect of fl-bP into the PS dewetting, and the selective PS etching of thin films revealed the presence of fl-bP flakes. Finally, a block copolymer/fl-bP composite (1.2 wt.%) was prepared via in situ reversible addition–fragmentation chain transfer (RAFT) polymerization by sonication-assisted exfoliation of bP into styrene. For this sample, ³¹P solid-state NMR and Raman spectroscopy confirmed an excellent preservation of bP structure.

Epoxidized Block and Statistical Copolymers Reinforced by Organophosphorus-Titanium-Silicon Hybrid Nanoparticles: Morphology and Thermal and Mechanical Properties

Glycidyl methacrylate (GMA) and a mixture of alkyl methacrylates (average chain length of 13 carbons; termed C13MA; derived from vegetable oils) were copolymerized by nitroxide-mediated polymerization to form epoxidized statistical and block copolymers with similar compositions (F GMA ∼0.8), which were further cross-linked by a bio-based diamine. Hybrid plate-like nanoparticles containing organophosphorus-titanium-silicon (PTS) with an average size of ∼130 nm and high decomposition temperature (485 °C) were synthesized via a hydrothermal reaction to serve as additives to simultaneously enhance the thermal and mechanical properties of the blend. Nanocomposites filled with PTS were prepared at different filler-loading levels (0.5, 2, 4 wt %). Transmission electron microscopy (TEM) of the cured block copolymer displayed reaction-induced macrophase-separated domains. TEM also showed an effective dispersion of PTS hybrids in the matrix without intense agglomeration. Thermogravimetric analysis at different heating rates revealed the activation energy of poly (GMA-stat-C13MA) at maximum decomposition increased from 143.5 to 327.2 kJ mol-1 with 4 wt % PTS. Decomposition temperature and char residue improved 12 °C and ∼7 wt %, respectively, and T g increased 12 °C by adding 4 wt % PTS. Targeting various PTS concentrations enabled tuning of the tensile modulus (up to 75%), tensile strength (up to 46%), and storage modulus in both glassy state (up to 59%) and rubbery plateau regions (up to 88%). Oscillatory frequency sweeps indicated that PTS makes the storage modulus frequency dependent, suggesting that the inclusion of the nanoparticles alters the relaxation of the surrounding matrix polymer.

Janus nanoparticles: an efficient intelligent modern nanostructure for eradicating cancer

In the modern age, the struggle to generate appropriate bio-based materials and nano-scaled colloidal particulates for developed application domains, has already resulted in remarkable attempts in the advancement of regulated size and shape, anisotropy, and characteristics of nanostructures. The bottom-up development strategies of components are among the most important science areas throughout nanotechnology, in which the designed building blocks are often utilized to generate novel structures by random self-assembly. In biomedical applications, Janus nanoparticles (JNPs) are necessary. This is due to their effective stimulus-responsive properties, tunable structure, biocompatibility, containing two surfaces with various hydrophobic characteristics and distinct functional groups. Featuring two parts with differing hydrophobicity has been the most critical aspect of the Janus amphiphilic particles. Development of JNPs has been afforded, using imaging agents (e.g. gold (AU) for photoacoustic imaging processing (PAI), silver for surface-enhanced Raman scattering (SERS), and Fe₃O₄ and MnO₂ to magnetic resonance imaging (MRI)). It is also to be mentioned that a number of other properties become salient - properties such as integration imaging factors into JNPs (like quantum dots, fluorescent dyes), multiple imaging methods for screening and diagnosis application can indeed be accomplished. Janus nanostructures have been promising platforms for bioengineering as therapeutic carriers, drug delivery vehicles, and biosensor equipment; they may also be employed for the transport of bioactive hydrophilic and hydrophobic materials. The main production approaches and major advancement of JNPs in the biomedical sector and cancer therapy will be described in this paper.

Block copolymer-nanodiamond coassembly in solution: towards multifunctional hybrid materials

Polymer-nanodiamond composites are excellent candidates for the fabrication of multifunctional hybrid materials. They integrate polymer flexibility and exceptional properties of nanodiamonds (NDs), such as biocompatibility, mechanical strength, color centers, and chemically-tailored surfaces. However, their development is hindered by the challenge of ensuring that NDs are homogeneously distributed in the composites. Here, we exploit colloidal coassembly between poly(isoprene-b-styrene-b-2-vinyl pyridine) (ISV) block copolymers (BCPs) and NDs to avoid ND self-agglomeration and direct ND spatial distribution. NDs were first air oxidized at 450 °C to obtain stable dispersions in dimethylacetamide (DMAc). By adding ISV into the dispersions, patchy hybrid micelles were formed due to H-bonds between NDs and ISV. The ISV-ND coassembly in DMAc was then used to fabricate nanocomposite films with a uniform sub-50 nm ND distribution, which has never been previously reported for an ND loading (φND) of more than 50 wt%. The films exhibit good transparency due to their well-defined nanostructures and smoothness and also exhibit an improved UV-absorption and hydrophilicity compared to neat ISV. More intriguingly, at a φND of 22 wt%, ISV and NDs coassemble into a network-like superstructure with well-aligned ND strings via a dialysis method. Transmission electron microscopy and dynamic light scattering measurements suggest a complex interplay between polymer-polymer, polymer-solvent, polymer-ND, ND-solvent, and ND-ND interactions during the formation of structures. Our work may provide an important foundation for the development of hierarchically ordered nanocomposites based on BCP-ND coassembly, which is beneficial for a wide spectrum of applications from biotechnology to quantum devices.

Copolymer-Based Fluorescence Nanosensor for In Situ Imaging of Homocysteine in the Liver and Kidney of Diabetic Mice

Homocysteine (Hcy) is one of the important biomarkers of clinical diagnosis, which is closely related to the occurrence and development of many diseases. Current analysis methods have difficulties in detecting Hcy in cells and living organisms. As a powerful technique, fluorescence methods combined the laser confocal imaging technology can achieve real-time visual tracking in cells and in vivo. Herein, we establish a conjugated copolymer-based fluorescence nanosensor (DPA-PFNP-Cu(II)) using the connected 2,7-dibromofluorene and 4,7-bis (2-bromothiophen-5-yl)-2-1-3-benzothiadiazole as the main chain. The competitive coordination between Hcy and Cu(II) allows the fluorescence of the polymer off to on. Finally, the nanosensor is applied for in situ imaging of Hcy levels in the kidney and liver of diabetic mice and is found that Hcy levels were positively correlated with the degree of diabetes. Notably, the depth of tissue penetration of the nanosensor enables Hcy detection of the liver and kidney through in vivo imaging without damage. Two-photon imaging and in vivo imaging achieve consistent results, which correct each other, improving the accuracy of the test result. The present works provide a new imaging technique for studying the occurrence and development of diabetes and screening of new drugs for treatment at the living level.

Nanoparticles influence miscibility in LCST polymer blends: from fundamental perspective to current applications

Polymer blending is an effective method that can be used to fabricate new versatile materials with enhanced properties. The blending of two polymers can result in either a miscible or an immiscible polymer blend system. This present review provides an in-depth summary of the miscibility of LCST polymer blend systems, an area that has garnered much attention in the past few years. The initial discourse of the present review mainly focuses on process-induced changes in the miscibility of polymer blend systems, and how the preparation of polymer blends affects their final properties. This review further highlights how nanoparticles induce miscibility and describes the various methods that can be implemented to avoid nanoparticle aggregation. The concepts and different state-of-the-art experimental methods which can be used to determine miscibility in polymer blends are also highlighted. Lastly, the importance of studying miscible polymer blends is extensively explored by looking at their importance in barrier materials, EMI shielding, corrosion protection, light-emitting diodes, gas separation, and lithium battery applications. The primary goal of this review is to cover the journey from the fundamental aspects of miscible polymer blends to their applications.

Tunable Assembly of Block Copolymer Tethered Particle Brushes by Surface-Initiated Atom Transfer Radical Polymerization

A strategy to synthesize SiO₂-g-PMMA/PMMA-b-PS mono- and bimodal block copolymer particle brushes by surface-initiated atom transfer radical polymerization (SI-ATRP) from silica particles is presented. First, PMMA blocks were prepared by normal ATRP with controlled degree of polymerizations and grafting density. In a second step, the PS block was synthesized through a chain extension using low parts per million of Cu catalyst. Variation of the SiO₂-g-PMMA-Br macroinitiator concentration had a pronounced effect on the modality of the chain extension product. In the limit of small concentration, partial termination resulted in bimodal brush architectures, while more uniform brush architectures were observed with increasing concentration of macroinitiator. Brush nanoparticles with bimodal architectures assembled into string-like aggregates that bore a resemblance to structures found in systems comprised of sparse (homopolymer) brush particles. The unexpected effect of modality on structure formation points to opportunities in controlling microstructures in brush particle materials.

Segregation of Maghemite Nanoparticles within Symmetric Diblock Copolymer and Triblock Terpolymer Patterns under Solvent Vapor Annealing

Block copolymers (BCPs), through their self-assembly, provide an excellent guiding platform for precise controlled localization of maghemite nanoparticles (MNPs). Diblock copolymers (di/BCP) represent the most applied matrix to host filler components due to their morphological simplicity. A series of nanocomposites based on diblock copolymer or triblock terpolymer matrices and magnetic nanoparticles were prepared to study and compare the influence of an additional block into the BCP matrix. MNPs were grafted with low molecular weight polystyrene (PS) chains in order to be segregated in a specific phase of the matrix to induce selective localization. After the mixing of the BCPs with 10% w/v PS-g-MNPs, nanocomposite thin films were formed by spin coating. Solvent vapor annealing (SVA) enabled the PS-g-MNPs selective placement within the PS domains of the BCPs, as revealed by atomic force microscopy (AFM). The recorded images have proven that high amounts of functionalized MNPs can be controllably localized within the same block (PS), despite the architecture of the BCPs (AB vs. ABC). The adopted lamellar structure of the “neat” BCP thin films was maintained for MNPs loading approximately up to 10% w/v, while, for higher content, the BCP adopted lamellar morphology is partially disrupted, or even disappears for both AB and ABC architectures.

Main Chain-Type Block Copolymers through Atom Transfer Radical Polymerization from Double-Decker-Shaped Polyhedral Oligomeric Silsesquioxane Hybrids

In this study, we synthesized two main chain-type block copolymers featuring hydrogen bond donor and acceptor segments through atom transfer radical polymerization (ATRP) using a bifunctionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the initiator. Hydrosilylation of vinylbenzyl chloride at the two corners of a double-decker silsesquioxane (DDSQ) provided the bifunctionalized benzyl chloride initiator VBC-DDSQ-VBC, which we applied as a platform to prepare a main chain-type polystyrene homopolymer (PS-DDSQ-PS), the diblock copolymer poly(styrene-b-4-vinylpyridine) (P4VP-b-PS-DDSQ-PS-b-P4VP), and the diblock copolymer poly(styrene-b-tert-butoxystyrene) (PtBuOS-b-PS-DDSQ-PS-b-PtBuOS) through sequential ATRP. Selective hydrolysis of the tert-butoxyl units of PtBuOS-b-PS-DDSQ-PS-b-PtBuOS yielded the strongly hydrogen bonding diblock copolymer poly (styrene-b-vinylphenol) (PVPh-b-PS-DDSQ-PS-b-PVPh). We used Fourier transfer infrared spectroscopy, nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, mass-analyzed laser desorption ionization mass spectrometry, and transmission electron microscopy to investigate the chemical structures, thermal behavior, and self-assembled nanostructures formed by these main chain-type block copolymers based on DDSQ.

Advanced Bottom-Up Engineering of Living Architectures

Bottom-up tissue engineering is a promising approach for designing modular biomimetic structures that aim to recapitulate the intricate hierarchy and biofunctionality of native human tissues. In recent years, this field has seen exciting progress driven by an increasing knowledge of biological systems and their rational deconstruction into key core components. Relevant advances in the bottom-up assembly of unitary living blocks toward the creation of higher order bioarchitectures based on multicellular-rich structures or multicomponent cell-biomaterial synergies are described. An up-to-date critical overview of long-term existing and rapidly emerging technologies for integrative bottom-up tissue engineering is provided, including discussion of their practical challenges and required advances. It is envisioned that a combination of cell-biomaterial constructs with bioadaptable features and biospecific 3D designs will contribute to the development of more robust and functional humanized tissues for therapies and disease models, as well as tools for fundamental biological studies.

Ptychographic X-ray tomography reveals additive zoning in nanocomposite single crystals

Single crystals containing nanoparticles represent a unique class of nanocomposites whose properties are defined by both their compositions and the structural organization of the dispersed phase in the crystalline host. Yet, there is still a poor understanding of the relationship between the synthesis conditions and the structures of these materials. Here ptychographic X-ray computed tomography is used to visualize the three-dimensional structures of two nanocomposite crystals - single crystals of calcite occluding diblock copolymer worms and vesicles. This provides unique information about the distribution of the copolymer nano-objects within entire, micron-sized crystals with nanometer spatial resolution and reveals how occlusion is governed by factors including the supersaturation and calcium concentration. Both nanocomposite crystals are seen to exhibit zoning effects that are governed by the solution composition and interactions of the additives with specific steps on the crystal surface. Additionally, the size and shape of the occluded vesicles varies according to their location within the crystal, and therefore the solution composition at the time of occlusion. This work contributes to our understanding of the factors that govern nanoparticle occlusion within crystalline materials, where this will ultimately inform the design of next generation nanocomposite materials with specific structure/property relationships.