Photonic Crystal Palette of Binary Block Copolymer Blends for Full Visible Structural Color Encryption

Structural color (SC) arising from a periodically ordered self-assembled block copolymer (BCP) photonic crystal (PC) is useful for reflective-mode sensing displays owing to its capability of stimuli-responsive structure alteration. However, a set of PC inks, each providing a precisely addressable SC in the full visible range, has rarely been demonstrated. Here, a strategy for developing BCP PC inks with tunable structures is presented. This involves solution-blending of two lamellar-forming BCPs with different molecular weights. By controlling the mixing ratio of the two BCPs, a thin 1D BCP PC film is developed with alternating in-plane lamellae whose periodicity varies linearly from ≈46 to ≈91 nm. Subsequent preferential swelling of one-type lamellae with either solvent or non-volatile ionic liquid causes the photonic band gap of the films to red-shift, giving rise to full-visible-range SC correlated with the pristine nanostructures of the blended films in both liquid and solid states. The BCP PC palette of solution-blended binary solutions is conveniently employed in various coating processes, allowing facile development of BCP SC on the targeted surface. Furthermore, full-color SC paintings are realized with their transparent PC inks, facilitating low-power pattern encryption.     

Thermo-Adaptive Block Copolymer Structural Color Electronics

Flexible electronics that enable the visualization of thermal energy have significant potential for various applications, such as thermal diagnosis, sensing and imaging, and displays. Thermo-adaptive flexible electronic devices based on thin 1D block copolymer (BCP) photonic crystal (PC) films with self-assembled periodic nanostructures are presented. By employing a thermo-responsive polymer/non-volatile hygroscopic ionic liquid (IL) blend on a BCP film, full visible structural colors (SCs) are developed because of the temperature-dependent expansion and contraction of one BCP domain via IL injection and release, respectively, as a function of temperature. Reversible SC control of the bi-layered BCP/IL polymer blend film from room temperature to 80 °C facilitates the development of various thermo-adaptive SC flexible electronic devices including pixel arrays of reflective-mode displays and capacitive sensing display. A flexible diagnostic thermal patch is demonstrated with the bi-layered BCP/IL polymer blend enabling the visualization of local heat sources from the human body to microelectronic circuits.     

Nanoparticle Arrays: Sub‐Nanometer Level Size Tuning of a Monodisperse Nanoparticle Array Via Block Copolymer Lithography (Adv. Funct. Mater. 2/2011)

The fabrication and catalytic application of a size‐tunable monodisperse nanoparticle array enabled by block copolymer lithography is demonstrated. Highly uniform vertical cylinder nanodomains are achieved in poly(styrene‐block‐4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer thin‐films by solvent annealing. The prominent diffusion of the anionic metal complexes into the protonated P4VP cylinder nanodomains occurs through specific electrostatic interactions in a weakly acidic aqueous solution. This well‐defined diffusion with nanoscale confinement enables preparation of the laterally ordered monodisperse nanoparticle array with sub‐nanometer level precise size tuning. The controlled growth of monodisperse nanoparticle arrays is proven by their catalytic use for vertical carbon nanotube (CNT) growth via plasma enhanced chemical vapor deposition (PECVD). Since the size of the catalyst particles is the decisive parameter for the diameters and wall‐numbers of CNTs, the highly selective growth of double‐walled or triple‐walled CNTs could be accomplished using monodisperse nanoparticle arrays.     

Integration of Polymer Synthesis and Self-Assembly for Controlled Periodicity and Photonic Properties

Materials chemistry and self-assembly properties are usually treated separately, largely limiting the real-time control of their nanostructures and resulting macroscopic properties in advanced self-assembled materials. This study shows a model system that integrates synthesis and self-assembly to achieve controlled periodicity and photonic properties in block copolymers (BCPs) at defined locations. First, the BCP thin films containing a pre-dissolved photo-initiator are swollen with monomer vapors. Upon exposure to UV light, the photoreaction synthesizes homopolymers within the film, which simultaneously blend with the BCPs and modify the periodicity in the exposed regions. This technique is successfully adapted to cylindrical polystyrene-b-polyisoprene-b-polystyrene and lamellar polystyrene-b-poly(2-vinyl pyridine) BCP thin films. This capability is especially useful in the practical application of photonic crystals, where it is shown that the stop band position of polystyrene-b-quaternized-poly(2-vinyl pyridine) photonic gel films can be successfully modulated in situ. A large-scale pattern is then fabricated by using a photomask. This study provides a model system for integrating materials synthesis and self-assembly to achieve spatially defined control over structural periodicity and macroscopic properties in self-assembled materials.     

pH‐Responsive Flower‐Type Micelles Formed by a Biotinylated Poly(2‐vinylpyridine)‐block‐poly(ethylene oxide)‐block‐poly(ε‐caprolactone) Triblock Copolymer

In the present work, a method is proposed to assemble pH‐responsive, flower‐like micelles that can expose a targeting unit at their periphery upon a decrease in pH. The micelles are composed of a novel biotinylated triblock copolymer of poly(εε‐caprolactone)‐block‐poly(ethylene oxide)‐block‐poly(2‐vinylpyridine) (PCL‐b‐PEO‐b‐P2VP) and the non‐biotinylated analogue. The block copolymers are synthesized by sequential anionic and ring‐opening polymerization. The pH‐dependent micellization behaviour in aqueous solution of the triblock copolymers developed is studied using dynamic light scattering, zeta potential, transmission electron microscopy (TEM), and fluorimetric measurements. The shielding of the biotin at neutral pH and their availability at the micelle surface upon protonation is established by TEM and surface plasmon resonance with avidin and streptavidin‐coated gold surfaces. The preliminary stealthy behavior of these pH‐responsive micelles is examined using the complement activation (CH50) test.     

Efficient Surface Neutralization and Enhanced Substrate Adhesion through Ketene Mediated Crosslinking and Functionalization

Balancing the interfacial interactions between a polymer and substrate is one of the most commonly employed methods to ensure the vertical orientation of nanodomains in block copolymer lithography. Although a number of technologies have been developed to meet this challenge, there remains a need for a universal solution for surface neutralization that combines simple synthesis, fast processing times, generality toward substrate, low density of film defects, and good surface adhesion. The chemistry of ketenes, which combines highly efficient polymer crosslinking through dimerization and surface adhesion through reaction with the substrate, is shown to be well suited to the challenge. The versatile chemistry of ketenes are accessed through the post‐polymerization of Meldrum's acid, which can be easily incorporated into copolymers through controlled radical polymerization processes. Further, the Meldrum's acid monomer is synthesized on a large scale in one step without the need for chromatography. Processing times of seconds, low defect density, simple synthetic procedures, and good substrate adhesion make these materials attractive as robust block copolymer neutralization layers.     

Regulation of Interphase Layer by Flexible Quasi-Solid Block Polymer Electrolyte to Achieve Highly Stable Lithium Metal Batteries (Adv. Funct. Mater. 27/2023)

Low safety, unstable interfaces, and high reactivity of liquid electrolytes greatly hinder the development of lithium metal batteries (LMBs). Quasi-solid-state electrolytes (QGPEs) with superior mechanical properties and high compatibility can meet the demands of LMBs. Herein, a biodegradable polyacrylonitrile/polylactic acid-block-ethylene glycol polymer (PALE) as membrane skeleton for GPEs is designed and systematically investigated by regulating the length and structure of the cross-linked chain. Benefiting from the enriched affinitive sites of polar functional groups ( CO,  C O C,  CN, and  OH) in highly cross-linked polymer structure, the designed PALE membrane skeleton exhibits flame-retardant property and ultrahigh liquid electrolyte uptake property, and the derived quasi-solid-state PALE GPEs deliver enhanced stretchability and a higher electrochemical stable window of 5.11 V. Besides, the PALE GPEs effectively protect cathodes from corrosion while allowing uniform and fast transfer of Li⁺ ions. Therefore, the Li||Li symmetrical battery and LFP or NCM811||Li full-cell using PALE GPEs exhibit excellent cycling stability coupled with compact and flat inorganic/organic interface layers. And the excellent cycling stability of pouch cells under harsh operating conditions indicates the application possibilities of PALE GPEs in flexible devices with high-energy-density.     

Micro‐Nanostructured Interfaces Fabricated by the Use of Inorganic Block Copolymer Micellar Monolayers as Negative Resist for Electron‐Beam Lithography

This paper introduces an approach where the match of two different length scales, i.e., pattern from self‐assembly of block copolymer micelles (< 100 nm) and electron‐beam (e‐beam) writing (> 50 nm), allow the grouping of nanometer‐sized gold clusters in very small numbers in even aperiodic pattern and separation of these groups at length scales that are not accessible by pure self‐assembly. Thus, we could demonstrate the grouping of Au nanoclusters in different geometries such as squares, rings, or spheres.     

Sub‐Nanometer Level Size Tuning of a Monodisperse Nanoparticle Array Via Block Copolymer Lithography

The fabrication and catalytic application of a size‐tunable monodisperse nanoparticle array enabled by block copolymer lithography is demonstrated. Highly uniform vertical cylinder nanodomains are achieved in poly(styrene‐block‐4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer thin‐films by solvent annealing. The prominent diffusion of the anionic metal complexes into the protonated P4VP cylinder nanodomains occurs through specific electrostatic interactions in a weakly acidic aqueous solution. This well‐defined diffusion with nanoscale confinement enables preparation of the laterally ordered monodisperse nanoparticle array with sub‐nanometer level precise size tuning. The controlled growth of monodisperse nanoparticle arrays is proven by their catalytic use for vertical carbon nanotube (CNT) growth via plasma enhanced chemical vapor deposition (PECVD). Since the size of the catalyst particles is the decisive parameter for the diameters and wall‐numbers of CNTs, the highly selective growth of double‐walled or triple‐walled CNTs could be accomplished using monodisperse nanoparticle arrays.     

Reactive Ion Etching of Cylindrical Polyferrocenylsilane Block Copolymer Micelles: Fabrication of Ceramic Nanolines on Semiconducting Substrates

The diblock copolymers, poly(isoprene‐block‐ferrocenyldimethylsilane) (PI‐b‐PFDMS) and poly(ferrocenyldimethylsilane‐block‐dimethylsiloxane) (PFDMS‐b‐PDMS), form cylindrical micelles with an organometallic polyferrocenylsilane core in a solvent of hexanes. These cylindrical micelles were deposited onto a Si substrate from solution by either spin or dip coating, and upon reactive ion etching, continuous ceramic nanolines with lengths of micrometers and widths as small as 8 nm were created. The nanolines were characterized by scanning force microscopy (SFM) and transmission electron microscopy (TEM), and were shown to contain Fe, Si, and O from X‐ray photoelectron spectroscopy (XPS) studies. The widths of the nanolines could be varied from ca. 8 to 30 nm, depending on the composition of the corona (PI or PDMS). The oriented deposition of these cylindrical micelles can be achieved along pre‐patterned grooves on a resist film using capillary forces. Following treatment with hydrogen or oxygen plasma, oriented ceramic nanolines can be fabricated. The approach reported here represents a relatively simple method to create ceramic nanolines with large aspect ratio on semiconducting substrates.     

Surface Segregation and Self-Assembly of Block-Copolymer Separation Layers on Top of Homopolymer Substructures in Asymmetric Ultrafiltration Membranes from a Single Casting Step

Surface segregation in blended polymer films has attracted much interest in fundamental research as well as for practical applications. A variety of methodologies have been proposed for controlling surface segregation. They often require long annealing times, however, to achieve thermodynamic equilibrium. Here, a strategy and proof-of-principle experiments are described to control surface segregation of thin block-copolymer (BCP) layers on top of a homopolymer in a single casting step from blended BCP/homopolymer solutions. The surface coverage by the minor constituent BCP (2–10 wt%) is accomplished despite almost identical surface energies of BCP and homopolymer constituents. Immersing this casted solution into water for nonsolvent induced phase separation (NIPS), a nonequilibrium process, affords solidified bilayer ultrafiltration membranes composed of a thin porous surface layer of self-assembled BCP atop an asymmetric porous homopolymer substructure. Key to successful BCP surface segregation is the choice of a binary solvent system based on careful considerations of solvent surface energies and polymer-solvent interaction parameters. Furthermore, stabilizing the BCP micellar structure by a divalent metal additive is also essential. The approach provides a cost-effective method for fabricating bilayer-type asymmetric ultrafiltration membranes with uniform BCP self-assembly based selective top surface pore layers in a single casting step.     

光响应液晶嵌段共聚物研究进展

光响应液晶嵌段共聚物综合了光响应性液晶和嵌段聚合物两类材料的优异特性,是一种多功能性的新型材料。其中以偶氮苯为代表的光响应基团作为液晶基元的嵌段共聚物是其目前研究的主体。本文对光响应液晶材料和嵌段聚合物分别做了简要介绍,阐述了它们各自的优势和特点。对于光响应液晶嵌段共聚物的光响应机理、相分离过程和有序化调控手段进行了重点探讨。在此基础上,介绍了其在光子学、有机纳米模板和聚合物胶束等方面的研究进展。     

Smart Nanostructured Materials based on Self‐Assembly of Block Copolymers

Nanoscale fabrication of smart materials relying on the molecular self‐assembly of block copolymers (BCPs) has been recognized as a valuable platform for various next‐generation functional structures. In this Progress Report, the recent advances in the BCP self‐assembly process, which has paved the way for viable applications of emerging nanotechnologies, are highlighted. Effective light‐induced self‐assembly based on photothermal annealing of high‐χ BCPs and conformal 3D surface nanopatterning exploiting chemically modified graphene flexible substrates are reviewed as the typical instances of advanced BCP‐based nanofabrication methodologies. Additionally, relevant potential application fields are suggested, namely, graphene nanoribbon field effect transistors, highly tunable refractive index metasurfaces for visible light, high‐sensitivity surface‐enhanced Raman spectroscopy, 2D transition metal dichalcogenide nanopatterning, sequential infiltration synthesis, and organic photovoltaics. Finally, the future research direction as well as innovative applications of these smart nanostructured materials is proposed.     

Vertical Orientation of Nanodomains on Versatile Substrates through Self‐Neutralization Induced by Star‐Shaped Block Copolymers

Vertical orientation of lamellar and cylindrical nanodomains of block copolymers on substrates is one of the most promising means for developing nanopatterns of next‐generation microelectronics and storage media. However, parallel orientation of lamellar and cylindrical nanodomains is generally preferred due to different affinity between two block segments in a block copolymer toward the substrate and/or air. Thus, vertical orientation of the nanodomains is only obtained under various pre‐ or post‐treatments such as surface neutralization by random copolymers, solvent annealing, and electric or magnetic field. Here, a novel self‐neutralization concept is introduced by designing molecular architecture of a block copolymer. Star‐shaped 18 arm poly(methyl methacrylate)‐block‐polystyrene copolymers ((PMMA‐b‐PS)₁₈) exhibiting lamellar and PMMA cylindrical nanodomains are synthesized. When a thin film of (PMMA‐b‐PS)₁₈ is spin‐coated on a substrate, vertically aligned lamellar and cylindrical nanodomains are obtained without any pre‐ or post‐treatment, although thermal annealing for a short time (less than 30 min) is required to improve the spatial array of vertically aligned nanodomains. This result is attributed to the star‐shaped molecular architecture that overcomes the difference in the surface affinity between PS and PMMA chains. Moreover, vertical orientations are observed on versatile substrates, for instance, semiconductor (Si, SiO_x), metal (Au), PS or PMMA‐brushed substrate, and a flexible polymer sheet of polyethylene naphthalate.     

光子晶体光纤

光子晶体光纤在光纤的几何结构、模式特性、色散及双折射性质等方面完全不同于传统的光纤。为此介绍了光子晶体光纤的一些重要特性、制作工艺和应用前景。     

光子晶体器件的研究进展及前景

光子晶体器件是近年来迅速发展起来的一类微纳器件,可以操控光子的运动行为,并具有损耗极低、体积小、易集成的优点。本文综合论述了光子晶体器件的几种主要设计方法的优缺点、指出了加工制作中的技术难点所在,还介绍了两种常用的耦合技术,最后对光子晶体的未来作了展望。     

Multifunctional Block Copolymers for Simultaneous Solubilization of Poorly Water‐Soluble Cholesterol and Hydroxyapatite Crystals

The solubilization of targeted compounds represents key criteria in the sophisticated field of medical chemistry but also in technical applications like scale removal. Especially, the simultaneous dissolution of two chemically different compounds remains challenging. Herein, macromolecular solubilizers are introduced for the simultaneous dissolution and encapsulation of poorly water‐soluble cholesterol and hydroxyapatite. The peptide‐based, amphiphilic block copolymers possess physicochemically disparate segments combined in one polymer chain as binding sites for hydrophobic as well as ionic materials. Small polymer libraries are synthesized and screened for structure–property relationships. Complementary analytical techniques suggest polymeric self‐assembly into spherical adaptive nanoparticles with the fundamental ability to passively absorb significant amounts of hydrophobic cholesterol up to 33 wt%. Furthermore, the additional incorporation of acidic domains enables the simultaneous dissolution of hydrophobic compounds and mineral phases such as hydroxyapatite. Ultimately, those nontoxic block copolymers can be used to solubilize and absorb other lipophilic and ionic compounds such as Sudan III dye and calcium ions. Such multifunctional nanomaterials have a wide range of direct application for simultaneous dissolution or delivery of hydrophobic molecules and cations resp. minerals for instance in the field of atherosclerosis.