Self-Assembly of block copolymers into internally ordered microparticles

Formation and Transformation of Polystyrene-block-poly(2-vinylpyridine) Hexasomes in the Solvent Exchange

The generation of inverse micellar nanostructures, especially those with open channels, using commercially available diblock copolymers (BCP), is vital for their wide applications in drug delivery and catalyst templating. However, the rigid requirements for forming inverse morphologies, such as the highly asymmetric molecular structures, the semicrystalline motifs, and concentrated solutions of diblock copolymers, represent obstacles to the development of successful strategies. In this study, the inverse polystyrene-block-poly(2-vinylpyridine) (PS_30K-b-P2VP_8.5K) micelles, i.e., the hexasomes with p6mm lattice, were generated through a modified solvent exchange via adding d-tartaric acid (d-TA) in the nonsolvent. Various intermediate morphologies have been identified with the change of d-TA concentration. Interestingly, in the high d-TA concentration (∼20 mg/mL), the hexasomes with close-packed hoops changed to mesoporous spheres with regularly packed perpendicular cylindrical channels (V_D-TA: V_BCP 6:100), and further to the mesoporous spheres with gyri-like open pores (V_D-TA: V_BCP > 15:100) with the increasing acidity in the mixed solvent. This study presents a simple and economical pathway for fabricating PS_30K-b-P2VP_8.5K hexasomes and first demonstrates these hexasomes can be modified to the morphology with open channels that will benefit their further applications.

A Versatile 3D-Confined Self-Assembly Strategy for Anisotropic and Ordered Mesoporous Carbon Microparticles

Mesoporous carbon microparticles (MCMPs) with anisotropic shapes and ordered structures are attractive materials that remain challenging to access. In this study, a facile yet versatile route is developed to prepare anisotropic MCMPs by combining neutral interface-guided 3D confined self-assembly (3D-CSA) of block copolymer (BCP) with a self-templated direct carbonization strategy. This route enables pre-engineering BCP into microparticles with oblate shape and hexagonal packing cylindrical mesostructures, followed by selective crosslinking and decorating of their continuous phase with functional species (such as platinum nanoparticles, Pt NPs) via in situ growth. To realize uniform in situ growth, a "guest exchange" strategy is proposed to make room for functional species and a pre-crosslinking strategy is developed to preserve the structural stability of preformed BCP microparticles during infiltration. Finally, Pt NP-loaded MCMPs are derived from the continuous phase of BCP microparticles through selective self-templated direct carbonization without using any external carbon source. This study introduces an effective concept to obtain functional species-loaded and N-doped MCMPs with oblate shape and almost hexagonal structure (p6mm), which would find important applications in fuel cells, separation, and heterogeneous catalysis.

Regioselective Seeded Polymerization in Block Copolymer Nanoparticles: Post-Assembly Control of Colloidal Features

Post-assembly modifications are efficient tools to adjust colloidal features of block copolymer (BCP) particles. However, existing methods often address particle shape, morphology, and chemical functionality individually. For simultaneous control, we transferred the concept of seeded polymerization to phase separated BCP particles. Key to our approach is the regioselective polymerization of (functional) monomers inside specific BCP domains. This was demonstrated in striped PS-b-P2VP ellipsoids. Here, polymerization of styrene preferably occurs in PS domains and increases PS lamellar thickness up to 5-fold. The resulting asymmetric lamellar morphology also changes the particle shape, i.e., increases the aspect ratio. Using 4-vinylbenzyl azide as co-monomer, azides as chemical functionalities can be added selectively to the PS domains. Overall, our simple and versatile method gives access to various multifunctional BCP colloids from a single batch of pre-formed particles.

Porous Polymer Cubosomes with Ordered Single Primitive Bicontinuous Architecture and Their Sodium-Iodine Batteries

Bicontinuous porous materials, which possess 3D interconnected pore channels facilitating a smooth mass transport, have attracted much interest in the fields of energy and catalysis. However, their synthesis remains very challenging. We report a general approach, using polymer cubosomes as the template, for the controllable synthesis of bicontinuous porous polymers with an ordered single primitive (SP) cubic structure, including polypyrrole (SP-PPy), poly-m-phenylenediamine (SP-PmPD), and polydopamine (SP-PDA). Specifically, the resultant SP-PPy had a unit cell parameter of 99 nm, pore diameter of 45 nm, and specific surface area of approximately 60 m²·g^-1. As a proof of concept, the I₂-adsorbed SP-PPy was employed as the cathode materials of newly emerged Na-I₂ batteries, which delivered a record-high specific capacity (235 mA·h·g^-1 at 0.5 C), excellent rate capability, and cycling stability (with a low capacity decay of 0.12% per cycle within 400 cycles at 1 C). The advantageous contributions of the bicontinuous structure and I₃^- adsorption mechanism of SP-PPy were revealed by a combination of ion diffusion experiments and theoretical calculations. This study opens a new avenue for the synthesis of porous polymers with new topologies, broadens the spectrum of bicontinuous-structured materials, and also develops a novel potential application for porous polymers.

Optically Transparent Polydimethylsiloxane-Ethylene Oxide-Propylene Oxide Multiblock Copolymers Crosslinked with Isocyanurates as Organic Compound Sorbents

New crosslinked (polydimethylsiloxane-ethylene-propylene oxide)-polyisocyanurate multiblock copolymers (MBCs) were synthesized, and their supramolecular structure and sorption characteristics were studied. It was found that the interaction of PPEG and D₄ leads to polyaddition of D₄ initiated by potassium-alcoholate groups. The use of the amphiphilic silica derivatives associated in an oligomeric medium (ASiPs) leads to structuring of the MBC due to the transetherification reaction of the terminal silanol groups of the MBC with ASiPs. It was established that the supramolecular structure of an MBC is built according to the “core-shell” structure. The obtained polymers were tested as sorbents for the development of new methods for the concentration and determination of inorganic compounds. The efficiency of sorption of reagents increased with an increase in the “thickness” of the polydimethylsiloxane component of the “shell” and with a decrease in the size of the polyisocyanurate “core”. The use of the obtained polymers as adsorbents of organic reagents is promising for increasing the efficiency of field methods of chemical testing and inorganic analysis, including the determination of the elemental composition and the detection of traces of contamination.

Effects of oppositely charged moieties on the self-assembly and biophysicochemical properties of polyurethane micelles

Gemini quaternary ammonium (GQA), a type of cationic surfactant, exhibits excellent micellization ability and acts as a cell internalization promoter to increase the permeability of the cell membrane. GQA is sensitive to ionic solutions, which disturb its stabilization and leads to the rapid degradation of its polymer micelles due to its unique hydrophilic N⁺ structure. However, the effect of negatively charged moieties in the polymer chains of GQA on its action in polymer micelles, typically with regard to its micellization and biological performance, remains unclear. In this work, a series of polyurethane micelles containing various ratios of oppositely charged moieties was prepared. We found that the interchain electrostatic interaction severely undermines the function of the GQA surfactant and hinders the self-assembly and stabilization of polyurethane micelles. Specifically, a hydrophilic corona with a longer length cannot completely overcome this effect. By regulating the ratio of oppositely charged moieties, micelles exhibited tunable biological properties, such as biocompatibility, cytotoxicity, cell internalization, and phagocytosis by macrophages. Based on our results, a moderate molecular weight of mPEG (Mn = 1900) and a slight positive surface potential (∼10 mV) are the best surface parameters for the comprehensive performance of the studied nanoplatforms. This study provides a further understanding of the electrostatic interaction effect on the properties of the cationic GQA, offering rational guidance for the design and fabrication of GQA polymer micelles.

Recent advances in versatile inverse lyotropic liquid crystals

Owing to the rapid and significant progress in advanced materials and life sciences, nanotechnology is increasingly gaining in popularity. Among numerous bio-mimicking carriers, inverse lyotropic liquid crystals are known for their unique properties. These carriers make accommodation of molecules with varied characteristics achievable due to their complicated topologies. Besides, versatile symmetries of inverse LCNPs (lyotropic crystalline nanoparticles) and their aggregating bulk phases allow them to be applied in a wide range of fields including drug delivery, food, cosmetics, material sciences etc. In this review, in-depth summary, discussion and outlook for inverse lyotropic liquid crystals are provided.

The Limited Palette for Photonic Block-Copolymer Materials: A Historical Problem or a Practical Limitation?

Block-copolymer self-assembly has proven to be an effective route for the fabrication of photonic films and, more recently, photonic pigments. However, despite extensive research on this topic over the past two decades, the palette of monomers and polymers employed to produce such structurally colored materials has remained surprisingly limited. In this Scientific Perspective, the commonly used block-copolymer systems reported in the literature are summarized (considering both linear and brush architectures) and their use is rationalized from the point of view of both their historical development and physicochemical constraints. Finally, the current challenges facing the field are discussed and promising new areas of research are highlighted to inspire the community to pursue new directions.

The Limited Palette for Photonic Block-Copolymer Materials: A Historical Problem or a Practical Limitation?

Block-copolymer self-assembly has proven to be an effective route for the fabrication of photonic films and, more recently, photonic pigments. However, despite extensive research on this topic over the past two decades, the palette of monomers and polymers employed to produce such structurally colored materials has remained surprisingly limited. In this Scientific Perspective, the commonly used block-copolymer systems reported in the literature are summarized (considering both linear and brush architectures) and their use is rationalized from the point of view of both their historical development and physicochemical constraints. Finally, the current challenges facing the field are discussed and promising new areas of research are highlighted to inspire the community to pursue new directions.

Noncovalent Postmodification Guided Reversible Compartmentalization of Polymeric Micelles

Compartmentalized micelles (CMs) are promising tailor-made soft matters that mimic natural designed structures and functions. Despite the structure of complex CMs, manipulating CM structures accessibly and reversibly remains elusive. Here, we report the fabrication of CMs via a generally valid noncovalent postmodification process. Starting from precursor micelles (PMs) based on one diblock copolymer, aromatic modification leads to the compartmentalization of PMs into well-defined spherical CMs. Control over compartment number, size and distribution in CMs, and segment distribution in their linear hierarchical assemblies is attained by simply tuning the postmodification degree and solvent composition. We also demonstrate the reversible transformation between PM and CMs during several heating-cooling cycles, which endows the micelles with potential in reversible functional transitions in situ close to nature's capability. Moreover, both hierarchically assembled or ill-structured micelles can rearrange into homogeneous CMs after one heating-cooling cycle, featuring the postmodification guided compartmentalization strategy with unprecedented micelle reproducibility.

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.

Pushing the limits of nanopore transport performance by polymer functionalization

Inspired by the design and performance of biological pores, polymer functionalization of nanopores has emerged as an evolving field to advance transport performance within the last few years. This feature article outlines developments in nanopore functionalization and the resulting transport performance including gating based on electrostatic interaction, wettability and ligand binding, gradual transport controlled by polymerization as well as functionalization-based asymmetric nanopore and nanoporous material design going towards the transport direction. Pushing the limits of nanopore transport performance and thus reducing the performance gap between biological and technological pores is strongly related to advances in polymerization chemistry and their translation into nanopore functionalization. Thereby, the effect of the spatial confinement has to be considered for polymer functionalization as well as for transport regulation, and mechanistic understanding is strongly increased by combining experiment and theory. A full mechanistic understanding together with highly precise nanopore structure design and polymer functionalization is not only expected to improve existing application of nanoporous materials but also opens the door to new technologies. The latter might include out of equilibrium devices, ionic circuits, or machine learning based sensors.

Confinement-Assembly of Terpolymer-based Janus Nanoparticles

While the confinement assembly of block copolymers (BCPs) into functional microparticles has been extensively studied, little is known about the behavior of Janus nanoparticles (JNPs) in spherical confinement. Here, we investigate the confinement self-assembly of JNPs in drying emulsion droplets and compare their behavior to their ABC triblock terpolymer precursor. Emulsions of both materials were prepared using Shirasu Porous Glass (SPG) membranes leading to narrow size distributions of the microparticles with average hydrodynamic radii in the range of R_h = 250 - 500 nm (depending on the pore radius, R_pore ). The internal structure of the microparticles was verified with transmission electron microscopy (TEM) on ultrathin cross-sections and compared to the corresponding bulk morphologies. While the confinement-assembly of terpolymers resulted in microparticles with ordered inner morphologies, order for JNPs diminished when the Janus balance (JB) deviated from parity. This article is protected by copyright. All rights reserved.

Self-Assembly of Copolymers Containing Crystallizable Blocks: Strategies and Applications

The self-assembly of copolymers containing crystallizable block in solution has received increasing attentions in the past few years. Various strategies including crystallization-driven self-assembly (CDSA) and polymerization-induced CDSA (PI-CDSA) have been widely developed. Abundant self-assembly morphologies were captured and advanced applications have been attempted. In this review, the synthetic strategies including the mechanisms and characteristics are highlighted, the survey on the advanced applications of crystalline nano-assemblies are collected. This review is hoped to depict a comprehensive outline for self-assembly of copolymers containing crystallizable block in recent years and to prompt the development of the self-assembly technology in interdisciplinary field. This article is protected by copyright. All rights reserved.

Effect of hydrophilic block end groups and block junction on block copolymer self-assembly in solution

Recent research suggests that the end groups of polymers can affect their self-assembly. However, the effect of end groups on the self-assembly of block copolymers in solution remains unclear, and thus far, only micelle-vesicle transformations have been achieved via end-group modification. Herein, we report that hydrophilic block end groups and the junction between two blocks can affect the solution self-assembly of block copolymers, leading to the formation of different morphologies, including vesicles, cubosomes, and hexosomes. Poly(ethylene glycol)-b-polystyrene (PEG-b-PS) with hydroxyl, methoxy, azido, or amino groups at the PEG chain ends was synthesized and self-assembled in solution via the cosolvent method. As a result, the morphology of the block copolymers transformed from vesicles to hexosomes upon increasing the end-group hydrophobicity. In addition, a morphological transition from cubosomes to vesicles was observed upon changing the junction from a triazole to an amide, and the interaction between the solvent and end groups significantly affected the self-assembly behavior.

Structure Regulation of Block Copolymer Assemblies in Emulsion Droplets by Adding a Selective Solvent

Generally, nanostructured polymer particles are prepared by three-dimensional (3D) confined self-assembly (3D-CSA) of block copolymers (BCPs), while micelles are obtained through self-assembly of BCPs in dilute solutions. Herein, a facile yet robust strategy is developed to regulate the assembled structures of BCP, poly(styrene-block-4-vinylpyridine) (PS-b-P4VP), from nanostructured particles to micelles. The assemblies are prepared by an emulsion-solvent diffusion-induced self-assembly route, which is conducted by dialysis. A key feature of this strategy is that a P4VP-selective solvent (e.g., ethanol) is added to the dialysate to tune the interfacial behavior of the droplets and assembled structures of PS-b-P4VP. Our results reveal that in the presence of slight ethanol, the surface and internal structural transitions of nanostructured particles are caused by changes in the interfacial selectivity and packing parameter. Interestingly, interfacial instability, which results in the formation of micelles, is observed when the dialysate contains 50 vol.% ethanol or more. The reason can be ascribed to the decreased interface tension, which is induced by the increase in ethanol and enhanced solubility of P4VP. This facile strategy provides a new opportunity to bridge the gap between traditional 3D-CSA and solution self-assembly of BCPs, offering a promising route to engineer morphologies and nanostructures of polymeric assemblies. This article is protected by copyright. All rights reserved.

Fluorine-containing nano-objects with the same compositions but different segment distributions: synthesis, characterization and comparison

PHOS-b-PPFS nano-objects and PPFS-b-PHOS nano-objects can be prepared by RAFT PISA and MISA processes, respectively. These nano-objects have the same compositions but different segment distributions and distinct hydrophilic/hydrophobic properties.

Topology-directed multi-tunable self-assembly of linear and tadpole-shaped amorphous-responsive-crystalline terpolymers

Rational design of ABC linear terpolymer and (c-AB)C tadpole-shaped terpolymer allows the construction of a topology-directed crystallization/thermo/pH-tunable hierarchical self-assembly platform.

Poly(vinylpyridine)-Containing Block Copolymers for Smart, Multicompartment Particles

Multicompartment particles generated by the self-assembly of block copolymers (BCPs) have received considerable attention due to their unique morphologies and functionalities. A class of important building blocks for multicomponent particles...

Morphology and Degradation of Multicompartment Microparticles Based on Semi-Crystalline Polystyrene-block-Polybutadiene-block-Poly(L-lactide) Triblock Terpolymers

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness.

Nonequilibrium Processes in Polymer Membrane Formation: Theory and Experiment

Porous polymer and copolymer membranes are useful for ultrafiltration of functional macromolecules, colloids, and water purification. In particular, block copolymer membranes offer a bottom-up approach to form isoporous membranes. To optimize permeability, selectivity, longevity, and cost, and to rationally design fabrication processes, direct insights into the spatiotemporal structure evolution are necessary. Because of a multitude of nonequilibrium processes in polymer membrane formation, theoretical predictions via continuum models and particle simulations remain a challenge. We compiled experimental observations and theoretical approaches for homo- and block copolymer membranes prepared by nonsolvent-induced phase separation and highlight the interplay of multiple nonequilibrium processes─evaporation, solvent-nonsolvent exchange, diffusion, hydrodynamic flow, viscoelasticity, macro- and microphase separation, and dynamic arrest─that dictates the complex structure of the membrane on different scales.

Amphiphilic triblock copolymer as the gas chromatographic stationary phase with high-resolution performance towards a wide range of isomers and the components of lemon essential oil

This work presents the investigation of using the amphiphilic triblock copolymer composed of poly(ethylene oxide)(PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) (denoted as EPE) as the stationary phase for gas chromatographic (GC) analyses. The EPE capillary column exhibited moderate polarity and column efficiency of 4348 plates/m determined by naphthalene at 120 °C (k = 11.52). Different from the PEG and polysiloxane homopolymers, it showed high-resolution performance towards a wide range of aliphatic and aromatic isomers in terms of polarity and acid-base properties. Particularly, the EPE column displayed distinct advantages for separating the critical isomers of alkanes, anilines and phenols and the components of the lemon essential oil over the commercial PEG and polysiloxane columns. In addition, the EPE column exhibited excellent separation repeatability and reproducibility with the relative standard deviation (RSD) values in the range of 0.03% - 0.08% for run-to-run, 0.14% - 0.61% for day-to-day and 3.1% - 4.0% for column-to-column, respectively. Moreover, the EPE column was investigated in terms of thermal stability, the minimum allowable operating temperature (MiAOT) and sample loadability. Its application to GC-MS analysis of the essential oil demonstrated its feasibility for practical analyses. This work demonstrates the promising future of triblock copolymers as a new class of selective stationary phases for GC analyses, which is barely reported up to date. The findings of this work is of important value for fundamental researches and practical applications.

Size-Controlled Formation of Polymer Janus Discs

A straightforward method is presented for the preparation of nano- to micrometer-sized Janus discs with controlled shape, size, and aspect ratio. The method relies on cross-linkable ABC triblock terpolymers and involves first the preparation of prolate ellipsoidal microparticles by combining Shirasu porous glass (SPG) membrane emulsification with evaporation-induced confinement assembly (EICA). By varying the pore diameter of the SPG membrane, we produce Janus discs with controlled size distributions centered around hundreds of nanometers to several microns. We further transferred the discs to water by mild sulfonation of PS to polystyrene sulfonic acid (PSS) and verified the Janus character by subsequent labelling with cationic nanoparticles. Finally, we show that the sulfonated Janus discs are amphiphilic and can be used as efficient colloidal stabilizers for oil-in-water (O/W) emulsions.

Photonic Particles Made by the Confined Self-Assembly of a Supramolecular Comb-Like Block Copolymer

Approaches that enable the preparation of robust polymeric photonic particles are of interest for the development of nonfading and highly reflective pigments for applications such as paints and display technologies. Here, the preparation of photonic particles that display structural color in both, aqueous suspension and the dry solid state is reported. This is achieved by exploiting the confined self-assembly of a supramolecular comb-like block copolymer (BCP) that microphase separates into a well-ordered lamellar morphology with dimensions that promote a photonic bandgap in the visible range. The comb-like BCP is formed by robust ionic interactions between poly(styrene-b-4-vinyl-pyridine) (PS-b-P4VP) BCP and dodecylbenzene sulfonic acid (DBSA), which selectively interacts with P4VP blocks. The components are combined in chloroform, and an aqueous emulsion is prepared. Evaporation of the organic solvent leads to the formation of solid microparticles with an onion-like 3D morphology. These photonic pigments display brilliant colors with reflectance spectra featuring pronounced optical bandgaps across the entire visible wavelength range with a peak reflectivity of 80-90%.

Polymer Vesicles for Antimicrobial Applications

Polymer vesicles, hollow nanostructures with hydrophilic cavity and hydrophobic membrane, have shown significant potentials in biomedical applications including drug delivery, gene therapy, cancer theranostics, and so forth, due to their unique cell membrane-like structure. Incorporation with antibacterial active components like antimicrobial peptides, etc., polymer vesicles exhibited enhanced antimicrobial activity, extended circulation time, and reduced cell toxicity. Furthermore, antibacterial, and anticancer can be achieved simultaneously, opening a new avenue of the antimicrobial applications of polymer vesicles. This review seeks to highlight the state-of-the-art of antimicrobial polymer vesicles, including the design strategies and potential applications in the field of antibacterial. The structural features of polymer vesicles, preparation methods, and the combination principles with antimicrobial active components, as well as the advantages of antimicrobial polymer vesicles, will be discussed. Then, the diverse applications of antimicrobial polymer vesicles such as wide spectrum antibacterial, anti-biofilm, wound healing, and tissue engineering associated with their structure features are presented. Finally, future perspectives of polymer vesicles in the field of antibacterial is also proposed.

Photoswitchable Surfactant-Driven Reversible Shape- and Color-Changing Block Copolymer Particles

Polymer particles that switch their shape and color in response to light are of great interest for the development of programmable smart materials. Herein, we report block copolymer (BCP) particles with reversible shapes and colors activated by irradiation with ultraviolet (UV) and visible lights. This shape transformation of the BCP particles is achieved by a spiropyran-dodecyltrimethylammoium bromide (SP-DTAB) surfactant that changes its amphiphilicity upon photoisomerization. Under UV light (365 nm) irradiation, the hydrophilic ring-opened merocyanine form of the SP-DTAB surfactant affords the formation of spherical, onion-like BCP particles. In contrast, when exposed to visible light, surfactants with the ring-closed form yield prolate or oblate BCP ellipsoids with axially stacked nanostructures. Importantly, the change in BCP particle morphology between spheres and ellipsoids is reversible over multiple UV and visible light irradiation cycles. In addition, the shape- and color-switchable BCP particles are integrated to form a composite hydrogel, demonstrating their potential as high-resolution displays with reversible patterning capabilities.

Self- and dis-assembly behavior of segmented wormlike nanostructures from an ABC triblock copolymer

Herein, we described the self-assembly of a triblock copolymer, poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO), in THF/water at room temperature to form segmented wormlike nanostructures. We found two different formation mechanisms of the segmented wormlike nanostructures from PS-b-P2VP-b-PEO with different molecular weights. Moreover, the dimension of such segmented wormlike nanostructures depends on the stirring rate. Interestingly, these wormlike nanostructures disassembled gradually when increasing the temperature, which is reversible. After cooling to room temperature the segmented wormlike micelles reformed gradually with stirring. Furthermore, neither intense stirring nor ultrasonic vibration could damage the structure of these wormlike nanostructures which proves their stability and potential application as drug delivery vehicles.

Nanoprecipitation as a simple and straightforward process to create complex polymeric colloidal morphologies

Polymeric nanoparticles are highly important functional nanomaterials for a large range of applications from therapeutics to energy. Advances in nanotechnology have enabled the engineering of multifunctional polymeric nanoparticles with a variety of shapes and inner morphologies. Thanks to its inherent simplicity, the nanoprecipitation technique has progressively become a popular approach to construct polymeric nanoparticles with precise control of nanostructure. The present review highlights the great capability of this technique in controlling the fabrication of various polymeric nanostructures of interest. In particular, we show here how the nanoprecipitation of either block copolymers or mixtures of homopolymers can afford a myriad of colloids displaying equilibrium (typically onion-like) or out-of-equilibrium (stacked lamellae, porous cores) morphologies, depending whether the system "freezes" while passing the glass transition or crystallization point of starting materials. We also show that core-shell morphologies, either from polymeric or oil/polymer mixtures, are attainable by this one-pot process. A final discussion proposes new directions to enlarge the scope and possible achievements of the process.

Kinetically Controlling the Length of Self-Assembled Polymer Nanofibers Formed by Intermolecular Hydrogen Bonds

Strong directional hydrogen bonds represent a suitable supramolecular force to drive the one-dimensional (1D) aqueous self-assembly of polymeric amphiphiles resulting in cylindrical polymer brushes. However, our understanding of the kinetics in these assembly processes is still limited. We here demonstrate that the obtained morphologies for our recently reported benzene tris-urea and tris-peptide conjugates are strongly pathway-dependent. A controlled transfer from solutions in organic solvents to aqueous environments enabled a rate-dependent formation of kinetically trapped but stable nanostructures ranging from small cylindrical or spherical objects (<50 nm) to remarkably large fibers (>2 μm). A detailed analysis of the underlying assembly mechanism revealed a cooperative nature despite the steric demands of the polymers. Nucleation is induced by hydrophobic interactions crossing a critical water content, followed by an elongation process due to the strong hydrogen bonds. These findings open an interesting new pathway to control the length of 1D polymer nanostructures.

Fluorescence Switchable Block Copolymer Particles with Doubly Alternate-Layered Nanoparticle Arrays

The precise self-assembly of block copolymers (BCPs) and inorganic nanoparticles (NPs) under 3D confinement offers microparticles with programmable nanostructures and functionalities. Here, fluorescence-switchable hybrid microspheres are developed by forming doubly alternating arrays of Au NPs and CdSe/ZnS quantum dots (QDs) within polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) BCP domains. These doubly alternating arrays afford controlled nonradiative energy transfer (NRET) between the QDs and Au NPs that is dependent on the layer-to-layer distance. Solvent-selective swelling of the hybrid particles tunes the distance between layers, modulating their NRET behavior and affording switchable fluorescence. The particle fluorescence is "OFF" in water through strong NRET from the QDs to Au NPs, but is "ON" in alcohols due to the increased distance between the Au NP and QD arrays in the swollen P4VP domains. The experimentally observed NRET intensity as a function of interparticle distance shows larger quenching efficiencies than those theoretically predicted due to the enhanced quenching within a 3D-confined system. Finally, the robust and reversible fluorescence switching of the hybrid particles in different solvents is demonstrated, highlighting their potentials for bioimaging, sensing, and diagnostic applications.

Recent Progress in Polymer Cubosomes and Hexosomes

Polymer cubosomes and hexosomes are polymer colloids with inverted lyotropic liquid crystal phases as internal structures. They are composed of regular networks of water-filled channels surrounded by a bilayer membrane made from amphiphilic block copolymers. Due to the uniform, tunable, and highly ordered porous structure, polymer cubosomes and hexosomes present numerous advantages over polymer micelles and vesicles, such as the high loading volumes for both hydrophilic and hydrophobic substances, large specific surface areas, and good mechanical and chemical stabilities. The polymer chemistry also enables unlimited molecular design to endow these polymer colloids with a lot of adjustable physical and chemical properties. Therefore, polymer cubosomes and hexosomes have attracted increasing attention for their potential applications in materials science and nanotechnology. This review outlines the recent progress in this field with an emphasis on the polymer architectures, the self-assembly conditions and mechanisms, and some application examples which are special for these inverted polymer colloids. It is hoped to provide some practical guidance for researchers interested in polymer cubosomes and hexosomes.

Self-assembled peptide and protein nanostructures for anti-cancer therapy: Targeted delivery, stimuli-responsive devices and immunotherapy

Self-assembled peptides and proteins possess tremendous potential as targeted drug delivery systems and key applications of these well-defined nanostructures reside in anti-cancer therapy. Peptides and proteins can self-assemble into nanostructures of diverse sizes and shapes in response to changing environmental conditions such as pH, temperature, ionic strength, as well as host and guest molecular interactions; their countless benefits include good biocompatibility and high loading capacity for hydrophobic and hydrophilic drugs. These self-assembled nanomaterials can be adorned with functional moieties to specifically target tumor cells. Stimuli-responsive features can also be incorporated with respect to the tumor microenvironment. This review sheds light on the growing interest in self-assembled peptides and proteins and their burgeoning applications in cancer treatment and immunotherapy.

Rapid Responsive Mechanochromic Photonic Pigments with Alternating Glassy-Rubbery Concentric Lamellar Nanostructures

Photonic pigment particles prepared via self-assembly have been suffering from their poor mechanical performances; i.e., they can easily be damaged and lose structural color under a compression force. This greatly limits their uses as mechanochromic pigments. Here, a nanoscale concentric lamellar structure of alternating glassy-rubbery microdomains is successfully created within photonic microparticles through a confined self-assembly and photo-cross-linking strategy. The glassy domain is composed of polystyrene, and cross-linked bottlebrush polydimethylsiloxane served as the supersoft elastic domain. The obtained photonic structure not only shows large deformation and visible color changes under a loaded compression force but also rapidly recovers to its original state in less than 1 s (∼0.16 s) upon unloading. Continuously loading-unloading micro compression test indicates that no obvious damage can be identified after 250 cycles, indicating the high durability of the pigments against deformation. These pigments with different reflected colors are simply obtained using bottlebrush block copolymer formulations with tunable weight percentages of polymer additives. The mechanical robust photonic pigments may be useful in many important applications.