Self-assembly Of Block Copolymers Research Articles

Tailored Nucleation-Growth Strategy for Precise Self-assembly of Block Copolymers.

The self-assembly of block copolymers (BCPs) to form nanostructures of various morphologies and controllable dimensions has been a very promising research area in nanotechnology in recent decades. This review mainly summarizes the recent advances in precise and controllable self-assembly of BCPs through a tailored nucleation-growth strategy to modulate the self-assembly behavior of the BCPs. These efforts have led to a better understanding of the self-assembly mechanisms and opened new possibilities for creating novel materials with designable properties. We hope that the review is more than a periodical summary of previous research work and can provide valuable inspiration for the research field.

Scalable and Precise Synthesis of Structurally Colored Bottlebrush Block Copolymers: Enabling Refined Color Calibration for Sustainable Photonic Pigments.

Self-assembled bottlebrush block copolymers (BBCPs) offer a vibrant, eco-friendly alternative to traditional toxic pigments and dyes, providing vivid structural colors with significantly reduced environmental impact. Scaling up the synthesis of these polymers for practical applications has been challenging with conventional batch methods, which suffer from slow mass and heat transfer, inadequate mixing, and issues with reproducibility. Precise control over molecular weight and dispersity remains a significant challenge for achieving finely tuned color appearances. Here, we present an alternative strategy to overcome the challenges by integrating a rapid continuous flow technique with an in-line self-assembly procedure. This strategy enables the rapid, stable and large-scale synthesis of narrow-dispersed BBCPs, exceeding 2 kg/day, a significant improvement over conventional gram-scale methods. Furthermore, precise control over the degree of polymerization is achieved with an unprecedented interval accuracy of four repeat units. This level of precision enables refined color calibration in the resulting photonic pigments, effectively eliminating the need for labor-intensive and costly multiple batch syntheses.

Nanoimprint lithography-assisted block copolymer self-assembly for hyperfine fabrication of magnetic patterns based on L10-FePt nanoparticles

Abstract L10-FePt-type bit-patterned media has provided a promising alternative for ultrahigh-density magnetic recording systems in the current digital era, but rapid fabrication of magnetic patterns with hyperfine bit islands is still challenging, especially with the target for miniaturization and scalable production simultaneously. Herein, Fe,Pt-containing block copolymers were utilized as single-source precursors for solution-processable patterning and subsequent generation of the demanding magnetic FePt dots by in situ pyrolysis. High-throughput nanoimprint lithography was initially employed to fabricate the predefined bit cells precisely, and then the intrinsic self-assembly of phase-separated block copolymers further drove the formation of accurate bit islands. Benefiting from the synergistic effect of top-down lithographic approach and bottom-up self-assembly, the customizable patterns could be achieved for large-scale mass production in targeted areas, but high-density isolated dots could also be accurately aligned along the patterned features after subsequent self-assembly. This reliable strategy would provide a good avenue to precisely construct ultrahigh-density magnetic data storage devices.

Precise Preparation of Size-Uniform Two-Dimensional Platelet Micelles Through Crystallization-Assisted Rapid Microphase Separation Using All-Bottlebrush-Type Block Copolymers with Crystalline Side Chains.

Polymer nanoparticles with low curvature, especially two-dimensional (2D) soft materials, are rich in functions and outstanding properties and have received extensive attention. Crystallization-driven self-assembly (CDSA) of linear semicrystalline block copolymers is currently a common method of constructing 2D platelets of uniform size. Although accompanied by high controllability, this CDSA method usually and inevitably requires a longer aging time and lower assembly concentration, limiting the large-scale preparation of nanoaggregates. In this study, a series of all-bottlebrush-type block copolymers, poly(octadecyl acrylate)-block-poly(oligoethylene glycol methyl ether methacrylate)s are prepared by living polymerization. Driven by the synergistic crystallization of crystalline side chains and the rapid microphase separation of bottlebrush topology, these polymers can assemble into uniform 2D circular platelet micelles in a few minutes, without being affected by a high assembly concentration. In this process, epitaxial growth of the bottlebrush molecules proceeds with rigid cylindrical molecular conformation at the micelle crystallization sites and eventually provides a sandwich-type micelle according to a head-to-head stacking mode. This is explained as a "crystallization-assisted rapid microphase separation" mechanism. The micelle structures are affected by the assembly solvent and temperature, the size of which shows a linear dependence on the assembly temperature below the melting point of the crystalline block, which can be used to precisely control the morphology of these 2D platelets. This study establishes an efficient and rapid method to prepare 2D polymer nanosoft materials, which are promising candidates for further development, preparation, and application of various nanomaterials.

Recent Progress in Block Copolymer Self-Assembly for the Fabrication of Structural Color Pigments.

The self-assembly of block copolymers (BCPs) into photonic materials has garnered increasing interest due to the versatility and ease of fabrication offered by the synthesized building blocks. BCPs are highly tunable, with their self-assembled structures' size being adjustable by modifying the block lengths, molecular weight(Mw), and polymer composition. This review provides a concise summary of the use of BCPs as photonic pigments, which generate color through structural manipulation rather than relying on chemical pigmentation. These photonic crystal pigments manipulate light behavior, including interference, diffraction, and diffusion, to generate specific colors. BCPs are categorized into two types: linear block copolymers (LBCPs) and brush block copolymers (BBCPs), each involving different monomers that form photonic crystals(PCs). The structural evolution and advancements of BCPs in various practical applications are also explored. It concludes by suggesting that structural color(SC) pigments based on eco-friendly PCs may replace traditional chemical ones in fields such as printing ink, biosensing, chemical sensing, and adaptive photonic materials.

Block Copolymer Self-Assembly for Biological and Chemical Sensing

Block Copolymer Self-Assembly for Biological and Chemical Sensing

Chlorophyll-Inspired Magnesium Porphyrin Array Membrane for Vis-Light-Enhanced Osmotic Energy Conversion.

Osmotic energy, a renewable clean energy, can be directly converted into electricity through ion-selective membranes. Inspired by the magnesium porphyrin (MgP) in plant chlorophyll, which absorbs vis-light and promotes photoelectric conversion, we demonstrate a MgP array membrane, realizing vis-light-enhanced ion transport regulation ability and osmotic energy conversion. The MgP arrays are self-assembled by a MgP-cored block copolymer under the coordination effect of block copolymer self-assembly and MgP π-π stacking, providing chloride-selective transport channels. Due to the unique photochemical properties of MgP, the chloride ion transport conductance and selectivity can be simultaneously increased under visible-light irradiation, benefiting the osmotic energy conversion. Specifically, the maximum power density increases from 26.7 to 34.5 W·m-2 after visible-light illumination, representing approximately a 30% increase. The construction of MgP arrays realizes photofacilitated osmotic energy conversion, providing an idea for designing an efficient photoelectric conversion system.

Neutral Interface Directed 3D Confined Self-Assembly of Block Copolymer: Anisotropic Patterned Particles with Ordered Structures.

Three-dimensional confined self-assembly (3D-CSA) of block copolymers (BCPs) is a distinctive and robust strategy that can yield colloidal polymer particles boasting ordered internal structures and diverse morphologies. The unique advantage of neutral interface lies in its ability to create anisotropic particles with surface patterns. The resulting unique polymer particles exhibit deformability under swelling, coupled with excellent spreadability and optical properties. These particles can also be used for fabrication of anisotropic nanoobjects or mesoporous particles via disassembly or serving as templates. This review comprehensively outlines the research advancements in neutral interface-guided 3D-CSA systems, including surfactant engineering, internal structure control, properties and future possibilities of anisotropic patterned particles.

Nitrogen-Doped Mesoporous Carbons Fabricated from Self-Assembled Block Copolymers for Electrochemical Production of H2O2

Nitrogen-doped mesoporous carbons are attracting significant attention as next-generation electrocatalytic materials due to their high specific surface area, high electrical conductivity, and exceptional chemical stability. Especially, due to the facilitated mass transport of products, high selectivity for the two-electron oxygen reduction reaction is expected, making it applicable to the synthesis of hydrogen peroxide (H2O2).¹ In this study, we focused on the soft template method by utilizing the self-assembly of a block copolymer (BCP) through microphase separation.² In our laboratory, we have been working on the synthesis of poly(4-vinylpyridine)-b-poly(2,2,2-trifluoroethyl methacrylate) (P4VP-b-PTFEMA). The significant repulsive interaction between these two components allows extensive control of the domain size. Furthermore, poly(4-vinylpyridine) serves as both the nitrogen and carbon sources and is selectively crosslinked by resol, thus enabling a high carbonization yield to be obtained. We employed this BCP as a soft template and introduce resol as a cross-linker for fabricating nitrogen-doped mesoporous carbons. Here, we investigated in detail the effects of the composition of the block copolymer and the amount of the crosslinker on the morphology and nitrogen content of the mesoporous carbon.P4VP-b-PTFEMA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A mixture of P4VP-b-PTFEMA and resol was dissolved in DMF at 5 wt%, and the solution was evaporated and dried under vacuum at 100 °C for 24 hours to prepare a composite film. Subsequently, the film was heated to 900 °C to fabricate nitrogen-doped mesoporous carbons.Small-angle X-ray scattering (SAXS) analysis of the composite film revealed various microphase-separated structures depending on the BCP-to-resol ratio (Fig. 1 (a)). Furthermore, nitrogen-doped mesoporous carbons with pore diameters ranging from 6.2 nm to 24 nm were fabricated using various molecular weights of PTFEMA (Fig. 1 (b)). Additionally, in our presentation, we will discuss how the pore size affects the selectivity of the two-electron reaction and the catalytic efficiency in the oxygen reduction reaction.[Reference](1) Park et al., ACS Catal. 2014, 4, 3749.(2) Liu et al., Polym. Chem. 2014, 5, 6452.[Acknowledgement]This study was financially supported by JSPS-KAKENHI(21K04828). Figure 1

Zwitterionic pyrazole functionalized PS-b-P4VP block copolymer membranes with enhanced Anti(−bio)fouling properties

Self-assembly of block copolymers (BCPs) offers numerous advantages in forming membranes with ordered porous architectures, showcasing their potential applications in membrane-based separation applications. However, the spontaneous accumulation of various foulants or biofoulants on the membrane surface severely hampers their practical applicability. Establishing stable functionalization of BCPs to create an anti(−bio)fouling surface without compromising the porous morphology of membranes is an ideal choice. In this context, we fabricated an isoporous membrane through the self-assembly of polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) BCP followed by covalent functionalization of pyridine moieties with zwitterionic pyrazolium moieties to obtain dual-charged (containing quaternized pyridinium and zwitterionic pyrazolium moieties) BCP-Py-Z membrane. The functionalization imparted anti(bio)fouling properties to the membranes. After post-functionalization, the quaternized pyridine and sulfobetaine pyrazolium moieties were thoroughly characterized using various techniques. Benefitting from this modification, the BCP-Py-Z membrane exhibited robust bactericidal properties against both E. coli and S. epidermidis bacteria and resulted in reduced fouling with organic compounds. Compared to the pristine BCP membrane, which is severely affected by fouling, the BCP-Py-Z membrane exhibits a much higher BSA rejection (∼95 %) and flux recovery (∼92%). Most importantly, the BCP-Py-Z membrane consistently maintained its water filtration and flux recovery tendency throughout the continuous dynamic fouling experiment cycle. This work embodies a straightforward and stable surface functionalization method to endow BCP membrane with a strong antifouling surface, which proves advantageous for various membrane-based filtration applications.

Molecular Dynamics and Self-Assembly in Double Hydrophilic Block and Random Copolymers.

We investigate the self-assembly and dynamics of double hydrophilic block copolymers (DHBCs) composed of densely grafted poly[oligo(ethylene glycol) methacrylate] (POEGMA) and poly(vinyl benzyl trimethylammonium chloride) (PVBTMAC) parent blocks by means of calorimetry, small- and wide-angle X-ray scattering (SAXS/WAXS), and dielectric spectroscopy. A weak segregation strength is evident from X-ray measurements, implying a disordered state and reflecting the inherent miscibility between the host homopolymers. The presence of intermixed POEGMA/PVBTMAC nanodomains results in homogeneous molecular dynamics, as evidenced through isothermal dielectric and temperature-modulated DSC measurements. The intermixed process undergoes a glass transition at a temperature approximately 40 K higher than the vitrification of bulk POEGMA segments, and it shifts to an even higher temperature by increasing the content of the hard block. At temperatures below the intermixed glass transition temperature, the confined POEGMA segments between the glassy intermixed regions contribute to a segmental process featuring (i) reduced glass transition temperature (Tg), (ii) reduced dielectric strength, (iii) broader distribution of relaxation times, and (iv) reduced fragility compared to the POEGMA homopolymer. We also observe two glass transition temperatures of dry PVBTMAC, which we attribute to the backbone and side chain segmental relaxation. To the best of our knowledge, this is the first time in the literature that these glass transitions of dry PVBTMAC have been reported. Finally, this study shows that excellent mixing of the two homopolymers is obtained, and this implies that different properties of this copolymer system can be tailored by adjusting the concentration of each homopolymer.

Fabrication of Ultrafine L10-FePt-Based Magnetic Patterns Enabled by Single-Step Nanoimprint-Assisted Block Copolymer Self-Assembly.

The bit islands in magnetic patterns play a crucial role in advancing magnetic recording density, but the trade-off issues between miniaturization and scalable production are still challenging. Here we present a two-in-one technique of nanoimprint lithography (NIL)-assisted self-assembly using a specially engineered FePt-containing block copolymer (BCP), offering a simple one-step fabrication for L10-FePt bit-patterned media with high throughput. This method combines top-down NIL with bottom-up self-assembly to precisely control the ultrafine magnetic bits in the nanoscale patterns. The FePt-derived BCPs, designed with an equal atomic ratio of Fe and Pt, ensure the preparation of homogeneously dispersed L10-FePt nanoparticles (NPs). Subsequent BCP pyrolysis results in NPs with enhanced magnetic properties, significantly advancing high-density data storage devices. This strategy offers a novel approach to drive the innovative creation of ordered magnetic metal alloy NPs arrays for practical applications.

Fabrication of model ultrafiltration membranes with uniform, high aspect ratio pores

In this manuscript, we report the facile fabrication of large-area model membranes with highly uniform and high aspect ratio pores with diameters <20 nm. These membranes are useful for fundamental investigations of separation by size exclusion in the ultrafiltration regime, where species to be separated from solution have dimensions of 1–100 nm. Such investigations require membranes with narrow pores and high aspect ratios such that the Hagen–Poiseuille equation is followed, enabling well-known models such as the hindered transport model to be evaluated and other affecting factors to be ignored. We demonstrate that the sub-20 nm pores in the membrane are of sufficiently high aspect ratio such that water flux through the membrane is consistent with the Hagen–Poiseuille equation. The fabrication relies on self-assembling block copolymers to form uniform, densely packed patterns with sub-20 nm resolution, sequential infiltration synthesis to convert the block copolymer in situ into a mask with adequate contrast to etch pores with an aspect ratio >5, and low-resolution photolithography to transfer the pattern over a large area into a silicon nitride membrane. Model membranes with narrow pore-size distribution fabricated in this way provide the means to investigate parameters that impact size-selective ultrafiltration separations such as the relationships between solute or particle size and pore size, their distributions, and rejection profiles, and, therefore, test the validity or limits of separation models.

Scalable Macroscopic Engineering from Polymer-Based Nanoscale Building Blocks: Existing Challenges and Emerging Opportunities.

Natural materials exhibit exceptional properties due to their hierarchical structures spanning from the nano- to the macroscale. Replicating these intricate spatial arrangements in synthetic materials presents a significant challenge as it requires precise control of nanometric features within large-scale structures. Addressing this challenge depends on developing methods that integrate assembly techniques across multiple length scales to construct multiscale-structured synthetic materials in practical, bulk forms. Polymers and polymer-hybrid nanoparticles, with their tunable composition and structural versatility, are promising candidates for creating hierarchically organized materials. This review highlights advances in scalable techniques for nanoscale organization of polymer-based building blocks within macroscopic structures, including block copolymer self-assembly with additive manufacturing, polymer brush nanoparticles capable of self-assembling into larger, ordered structures, and direct-write colloidal assembly. These techniques offer promising pathways toward the scalable fabrication of materials with emergent properties suited for advanced applications such as bioelectronic interfaces, artificial muscles, and other biomaterials.

Self-Assembly of Hierarchical Silicon-Containing Block Copolymers with Cross-Linkable 3 nm Smectic Motifs for Nanopatterning and Osmotic Energy Conversion Membranes.

Highly-dense small-feature-size nanopatterns and nanoporous membranes are important in advanced microelectronics, nanofiltration, and biomimic device manufacturing. Here, we report the synthesis and self-assembly of a series of high-interaction-parameter (high-χ) silicon-containing hierarchical block copolymers (BCPs) with cross-linkable subordering chalcone motifs, which possess both an intrinsic native etching contrast for nanofabrication and cross-linkability under ultraviolet light for generating free-standing membranes. BCPs with a volume fraction of chalcone block of 55-74% form ordered primary nanostructures with period 15-22 nm including lamellae, double gyroid, hexagonally packed cylinders, and body-centered cubic spheres of the minority Si-containing block. The majority PChMA block self-assembles into a highly ordered 3 nm smectic sublattice, and cross-linking after self-assembly enables the formation of free-standing isoporous membranes. Both silicon oxide nanopatterns and free-standing nanoporous osmotic energy conversion membranes are generated by etching films of these BCPs. This work demonstrates that the combination of hierarchical ordering and cross-linkable motifs in a high-interaction parameter BCP enables applications in both nanofabrication and free-standing functional porous membranes.

LOCAL DIELECTRIC SPECTROSCOPY AND ITS APPLICATION TO POLYMERS

ABSTRACT The advent of nanodielectrics, nanocomposite materials based on a polymeric matrix, and materials with physical properties ruled by interfacial effects in general demands techniques to characterize functional properties on a local scale with high spatial resolution. Scanning probe microscopies (SPMs), in their electrical modes, have emerged as indispensable tools to access physical quantities such as dielectric constant, surface potential, and static charge, with nanometer-scale lateral resolution and with surface selectivity, being influenced mainly by the outermost layer of the specimen. In this tribute, the development of various SPM electrical modes is illustrated, focusing on the measurement of dielectric permittivity and its spectroscopic extension to access the local, frequency-dependent dielectric function (local dielectric spectroscopy [LDS]). The application to nanostructured polymers in the form of ultrathin films, nanometer-scale–separated blends, and self-assembled block copolymer structures is described. LDS appears to be a promising technique for characterizing the electric properties of polymers and their composites as well as other glass formers and nanostructured systems.

Block Copolymer-Directed Single-Diamond Hybrid Structures Derived from X-ray Nanotomography.

Block copolymers are recognized as a valuable platform for creating nanostructured materials. Morphologies formed by block copolymer self-assembly can be transferred into a wide range of inorganic materials, enabling applications including energy storage and metamaterials. However, imaging of the underlying, often complex, nanostructures in large volumes has remained a challenge, limiting progress in materials development. Taking advantage of recent advances in X-ray nanotomography, we noninvasively imaged exceptionally large volumes of nanostructured hybrid materials at high resolution, revealing a single-diamond morphology in a triblock terpolymer-gold composite network. This morphology, which is ubiquitous in nature, has so far remained elusive in block copolymer-derived materials, despite its potential to create materials with large photonic bandgaps. The discovery was made possible by the precise analysis of distortions in a large volume of the self-assembled diamond network, which are difficult to unambiguously assess using traditional characterization tools. We anticipate that high-resolution X-ray nanotomography, which allows imaging of much larger sample volumes than electron-based tomography, will become a powerful tool for the quantitative analysis of complex nanostructures and that structures such as the triblock terpolymer-directed single diamond will enable the generation of advanced multicomponent composites with hitherto unknown property profiles.

Biocompatible Glycopolymer-PLA Amphiphilic Hybrid Block Copolymers with Unique Self-Assembly, Uptake, and Degradation Properties.

The self-assembly of Janus-type amphiphilic hybrid block copolymers composed of hydrophilic/hydrophobic layers has shown promise for drug encapsulation and delivery. Saccharides have previously been incorporated to improve the biocompatibility of self-assembled structures; however, glycopolymer block copolymers have been less explored, and their structure-property relationships are not well understood. In this study, novel glycopolymer-branched poly(lactic acid) (PLA) block copolymers were synthesized via thiol-ene coupling and their composition-dependent morphologies were elucidated. Stability as a function of pH, dye uptake capabilities, and cytotoxicity were evaluated. Systems with a hydrophilic weight ratio of 30% were found to produce bilayer nanoparticles, while systems with a hydrophilic weight ratio of 60% form micelles upon self-assembly in aqueous media. Regardless of composition and morphology, all systems exhibited uptake of both hydrophobic (curcumin, DL % from 4.25 to 11.55) and hydrophilic (methyl orange, DL % from 4.08 to 5.88) dye molecules with release profiles dependent on composition. Furthermore, all of the nanoparticles exhibited low cytotoxicity, confirming their potential for biomedical applications.

Contact Hole Shrinkage: Simulation Study of Resist Flow Process and Its Application to Block Copolymers.

For vertical interconnect access (VIA) in three-dimensional (3D) structure chips, including those with high bandwidth memory (HBM), shrinking contact holes (C/Hs) using the resist flow process (RFP) represents the most promising technology for low-k1 (where CD=k1λ/NA,CD is the critical dimension, λ is wavelength, and NA is the numerical aperture). This method offers a way to reduce dimensions without additional complex process steps and is independent of optical technologies. However, most empirical models are heuristic methods and use linear regression to predict the critical dimension of the reflowed structure but do not account for intermediate shapes. In this research, the resist flow process (RFP) was modeled using the evolution method, the finite-element method, machine learning, and deep learning under various reflow conditions to imitate experimental results. Deep learning and machine learning have proven to be useful for physical optimization problems without analytical solutions, particularly for regression and classification tasks. In this application, the self-assembly of cylinder-forming block copolymers (BCPs), confined in prepatterns of the resist reflow process (RFP) to produce small contact hole (C/H) dimensions, was described using the self-consistent field theory (SCFT). This research paves the way for the shrink modeling of the enhanced resist reflow process (RFP) for random contact holes (C/Hs) and the production of smaller contact holes.

Ionophore-based nanospheres enable selective and sensitive fluorescence detection of copper ions

A novel ionophore-based fluorescent nanosensor has been successfully fabricated for the sensitive and selective detection of Cu2+ ions. The nanosensor was constructed through self-assembly of amphiphilic block copolymers, incorporating elesclomol as a Cu2+ ionophore and long-chain dialkylcarbocyanines (DiD) as a fluorescent dye. This design exhibits an "ON/OFF" fluorescence response, where Cu2⁺ ions are selectively sequestered within the nanosensors, resulting in fluorescence quenching of DiD. This strategy enables rapid and highly selective Cu2⁺ sensing with remarkable fluorescence quenching efficiency (up to 93.5 %) and an exceptionally low detection limit of 28.6 nM. The linear detection range extends over two orders of magnitude (0.05–10 μM). Furthermore, the feasibility of this nanosensor for practical applications was confirmed through successful determination of Cu2+ in real water and beer samples, with excellent recovery rates. This nanosensor offers advantages of simplicity, rapidity, and cost-effectiveness, holding significant potential for sensitive and selective Cu2+ detection in various biological and environmental samples.