Scalable,Versatile Synthesis of Ultrathin Polyetherimide Films and Coatings via Interfacial Polymerization

Polyetherimides (PEI) are high-performance thermoplastic polymers featuring a high dielectric constant and excellent thermal stability. In particular, PEI thin films are of increasing interest for use in solid-state capacitors and membranes, yet the cost and thickness are limited by conventional synthesis and thermal drawing techniques. Here, a method of synthesizing ultrathin PEI films and coatings is introduced based on interfacial polymerization (IP) of poly(amic acid), followed by thermal imidization. Control of transport, reaction, and precipitation kinetics enables tailoring of PEI film morphology from a nanometer-scale smooth film to a porous micrometer-scale layer of polymer microparticles. At short reaction times (≈1 min) freestanding films are formed with ≈1 µm thickness, which to our knowledge surpass commercial state-of-the-art films (3–5 µm minimum thickness) made by thermal drawing. PEI films synthesized via the IP route have thermal and optical properties on par with conventional PEI. The use of the final PEI is demonstrated in structurally colored films, dielectric layers in capacitors, and show that the IP route can form nanometer-scale coatings on carbon nanotubes. The rapid film formation rate and fine property control are attractive for scale-up, and established methods for roll-to-roll processing can be applied in future work.     

Interfacial Self‐Assembly of Amphiphilic Dual Temperature Responsive Actuating Janus Particles

Amphiphilic Janus particles feature the combination of two different functional materials in one single colloid, as well as the possibility of self‐assembly at interfaces into complex superstructures. In this article, the self‐assembly of dual temperature responsive amphiphilic Janus particles at liquid–liquid interfaces and their subsequent conversion into an actuating layer‐shaped surface are presented. These microparticles are produced in a capillaries based continuous flow microfluidic device by photoinitiated radical polymerization. The hydrophobic part of the Janus particles contains a liquid crystalline elastomer (LCE), which performs a strong actuation up to 95% during the nematic–isotropic phase transition. The other side consists of a p(NIPAAm) hydrogel, which features volumetric expansions up to 280% below the lower critical solution temperature. A multistep molding process is developed to uniformly align the Janus particles at a toluene/water boundary surface and to embed the particles into a hydrogel matrix. A particle covered hydrogel layer is obtained, which features a collective actuation of the rod‐like LCE parts on the surface and a bundling of the resulting forces during the phase transition.     

Compartmentalized Thin Films with Customized Functionality via Interfacial Cross‐linking of Protein Cages

Hybrid thin films with a high loading and homogeneous dispersion of functional nanoparticles (and/or molecules) find applications in (bio)‐sensors and electronic devices. The fabrication of such hybrid thin films, however, suffers from the complex and diverse surface and physicochemical properties of individual nanoparticles. To address this challenge, a facile and general strategy toward compartmentalized thin films through the interfacial cross‐linking of viral protein cages is reported. Employing these protein cages, gold nanoparticles, as well as enzyme horseradish peroxidase, are encapsulated into virus‐like particles and then cross‐linked into thin films with a thickness varying from monolayer to submicron dimensions. These compartmentalized thin films not only ensure that the cargo is homogeneously dispersed, but also display good catalytic activity. This strategy is, in principle, applicable for a wide range of (bio)‐organic nanocontainers, enabling the versatile fabrication of 2D thin films with extensive application prospects.     

Contactless Interfacial Thin-Film Breaking Caused Splash-Like Demulsification of Floating Micron Emulsions via Ionic Wind

Emulsified oil leakage onto the bulk water surface causes severe issues on global ecology and health. Developing efficient, rapid, and universal separation methods of emulsions has been a significant topic in scientific studies. However, a contactless and additive-free strategy to achieve continuous floating emulsion separation and oil collection remains to be discovered. Herein, a universal contactless demulsification, transportation, and collection method to dispose floating emulsions by ionic wind, which contains active charged particles generated by corona discharge is reported. The splash-like demulsification process of floating emulsions is attributed to the rupture of water film enveloped on oil droplet surface, simultaneously and respectively. The evidence of this process recorded by a high-speed camera with 20 000 fps has a referential significance for other works. This study may clean up universal floating emulsions discharged on water in real situations such as oil stations, chemical plants, and restaurants, and furthermore increase the potential of remote control in liquid dynamics by corona discharge.     

工艺条件对PZT薄膜界面层电容的影响

采用了一种新的界面层电容计算方法来提取PZT薄膜与电极之间的界面层电容,使用这种方法对不同工艺条件下制备的PZT薄膜界面层电容进行了比较.通过实验发现,不同的Pt溅射温度和PZT薄膜的退火温度都会对PZT薄膜与电极之间的界面层产生影响.高温溅射Pt会破坏Pt衬底中的TiO2结构,并导致PZT薄膜与电极之间的界面层特性变差;PZT薄膜600℃退火得到的薄膜表面均匀致密,界面层电容值最大.通过不同工艺条件下PZT薄膜界面层电容的提取比较,获得了调整PZT薄膜工艺条件的优化参数.     

Highly Oriented Nanofibrils of Regioregular Poly(3‐hexylthiophene) Formed via Block Copolymer Self‐Assembly in Liquid Crystals

A novel method making use of block copolymer self‐assembly in nematic liquid crystals (LCs) is described for preparing macroscopically oriented nanofibrils of π‐conjugated semiconducting polymers. Upon cooling, a diblock copolymer composed of regioregular poly(3‐hexylthiophene) (P3HT) and a liquid crystalline polymer (LCP) in a block‐selective LC solvent can self‐assemble into oriented nanofibrils exhibiting highly anisotropic absorption and polarized photoluminescence emission. An unusual feature of the nanofibrils is that P3HT chains are oriented along the fibrils' long axis. This general method makes it possible to use LCs as an anisotropic medium to grow oriented nanofibrils of many semiconducting polymers insoluble in LCs.     

Block Copolymer Packing Limits and Interfacial Reconfigurability in the Assembly of Periodic Mesoporous Organosilicas

Here poly(N,N‐dimethylacrylamide)‐block‐poly(styrene) block copolymer micelles (BCPs) are advanced and applied to assemble periodic mesoporous organosilicas (PMOs) with noncylindrical pores. Using these BCP micelles, it is found that pore dimensions (11–23 nm), wall thicknesses (5–9 nm), and overall porosities (26%–78%) are independently programable, depending only on relative inputs for BCP and matrix former. Notably, the degree of order in all films improves as BCP loading approaches a packing limit of 63 vol%. Beyond this limit and regardless of pore dimensions, both porogen packing in the film and pore structure after thermal processing show significant deviations away from spherical close‐packed lattices. The surprising absence of film collapse in this regime allows here to quantify the evolution of pore structure through the thermally driven interfacial reconfigurability of BCP micelles in the hybrid films when porogen loading exceeds the packing limit by using both scattering techniques and scanning transmission electron microscopy tomography. Finally, the PMOs here give dielectric constants of 1.2 and 1.5 above and below the BCP packing limit, respectively—the lowest ever reported for this matrix material.     

Self‐Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores

We report the self‐assembly and characterization of mesoporous silica thin films with a 3D ordered arrangement of isolated spherical pores. The preparation method was based on solvent‐evaporation induced self‐assembly (EISA), with MTES (CH₃–Si(OCH₂CH₃)₃) as the silica precursor and a polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymer as the structure‐directing agent. The synthetic approach was designed to suppress the siloxane condensation rate of the siloxane network, allowing co‐self‐assembly of the silica and the amphiphile, followed by retraction of the PEO chains from the silica matrix and matrix consolidation, to occur unimpeded. The calcined films retained the methyl ligands and exhibited no measurable microporosity, thereby indicating that the 3D‐ordered spherical mesopores are not interconnected. A solvent‐mediated formation mechanism is proposed for the absence of microporosity. Due to their closed porosity and hydrophobicity, the MTES‐based films and MTES‐TEOS (Si(OCH₂CH₃)₄)‐based hybrid films we describe should be promising for applications such as low‐k dielectrics.     

Self‐Assembly of Nanostructured,Complex, Multication Films via Spontaneous Phase Separation and Strain‐Driven Ordering

Spontaneous self‐assembly of a multication nanophase in another multication matrix phase is a promising bottom‐up approach to fabricate novel, nanocomposite structures for a range of applications. In an effort to understand the mechanisms for such self‐assembly, complimentary experimental and theoretical studies are reported to first understand and then control or guide the self‐assembly of insulating BaZrO₃ (BZO) nanodots within REBa₂Cu₃O_7–δ (RE = rare earth elements including Y, REBCO) superconducting films. The strain field developed around BZO nanodots embedded in the REBCO matrix is a key driving force dictating the self‐assembly of BZO nanodots along REBCO c‐axis. The size selection and spatial ordering of BZO self‐assembly are simulated using thermodynamic and kinetic models. The BZO self‐assembly is controllable by tuning the interphase strain field. REBCO superconducting films with BZO defect arrays self‐assembled to align in both vertical (REBCO c‐axis) and horizontal (REBCO ab‐planes) directions result in the maximized pinning and J_c performance for all field angles with smaller angular J_c anisotropy. The work has broad implications for the fabrication of controlled self‐assembled nanostructures for a range of applications via strain‐tuning.     

Electrically Conductive Thin Films Prepared from Layer‐by‐Layer Assembly of Graphite Platelets

Layer‐by‐layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/ββ‐methacryl‐oxyethyl‐trimethyl‐ammonium copolymer as the cationic binder. Nanoparticle zeta (ζζ) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field‐emission scanning electron microscopy and atomic‐force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self‐assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21 nm. Thin‐film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6 mΩ cm^?2 at 173 nm to 3.5 mΩ cm^?2 at 276 nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly.     

Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers

The charge separation efficiency of water oxidation photoanodes is modulated by depositing polyelectrolyte multilayers on their surface using layer‐by‐layer (LbL) assembly. The deposition of the polyelectrolyte multilayers of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonate) induces the formation of interfacial dipole layers on the surface of Fe₂O₃ and TiO₂ photoanodes. The charge separation efficiency is modulated by tuning their magnitude and direction, which in turn can be achieved by controlling the number of bilayers and type of terminal polyelectrolytes, respectively. Specifically, the multilayers terminated with anionic poly(styrene sulfonate) exhibit a higher charge separation efficiency than those with cationic counterparts. Furthermore, the deposition of water oxidation molecular catalysts on top of interfacial dipole layers enables more efficient photoelectrochemical water oxidation. The approach exploiting the polyelectrolyte multilayers for improving the charge separation efficiency is effective regardless of pH and types of photoelectrodes. Considering the versatility of the LbL assembly, it is anticipated that this study will provide insights for the design and fabrication of efficient photoelectrodes.     

Rapid Fabrication of Two‐ and Three‐Dimensional Colloidal Crystal Films via Confined Convective Assembly

We have developed a self‐assembly method for fabricating well‐ordered two‐dimensional (2D) and three‐dimensional (3D) colloidal crystal films. With a minute amount of a polystyrene colloidal suspension and without any special equipment, the proposed method can be used to rapidly deposit high‐quality colloidal crystal films over a large surface area. By controlling the lift‐up rate of the substrate, we modulate the meniscus thinning rate, which determines whether the colloidal particles are assembled into two or three dimensions. The proposed method can be used to fabricate not only monolayered colloidal crystals with colloidal particles of various sizes, but also multilayered colloidal crystals. In addition, the method enables us to fabricate binary colloidal crystals by consecutively depositing large and small particles.     

Molten‐Salt‐Assisted Self‐Assembly (MASA)‐Synthesis of Mesoporous Metal Titanate‐Titania,Metal Sulfide‐Titania,and Metal Selenide‐Titania Thin Films

New synthetic strategies are needed for the assembly of porous metal titanates and metal chalcogenite‐titania thin films for various energy applications. Here, a new synthetic approach is introduced in which two solvents and two surfactants are used. Both surfactants are necessary to accommodate the desired amount of salt species in the hydrophilic domains of the mesophase. The process is called a molten‐salt‐assisted self‐assembly (MASA) because the salt species are in the molten phase and act as a solvent to assemble the ingredients into a mesostructure and they react with titania to form mesoporous metal titanates during the annealing step. The mesoporous metal titanate (meso‐Zn₂TiO₄ and meso‐CdTiO₃) thin films are reacted under H₂S or H₂Se gas at room temperature to yield high quality transparent mesoporous metal chalcogenides. The H₂Se reaction produces rutile and brookite titania phases together with nanocrystalline metal selenides and H₂S reaction of meso‐CdTiO₃ yields nanocrystalline anatase and CdS in the spatially confined pore walls. Two different metal salts (zinc nitrate hexahydrate and cadmium nitrate tetrahydrate) are tested to demonstrate the generality of the new assembly process. The meso‐TiO₂‐CdSe film shows photoactivity under sunlight.     

Assembly of Layered Rare‐Earth Hydroxide Nanosheets and SiO2 Nanoparticles to Fabricate Multifunctional Transparent Films Capable of Combinatorial Color Generation

Colloidal solutions of layered rare‐earth hydroxide nanosheets provide a simple route to deposit ultra thin luminescence films. The antireflection and antifogging properties were integrated into transparent luminescent films by the layer‐by‐layer assembly of Eu³⁺, Tb³⁺, Dy³⁺ doped‐hydroxocation nanosheets and negatively‐charged SiO₂ nanoparticles. Resulting multifunctional films exhibited efficient red, green, and blue emissions with controllable intensity. Highly improved transmittance enabled us to display combinatorial color luminescence, which can be achieved by multiply overlapping individual films with different combinations, without significant loss of transparency. Triple overlap of red/green/blue films generated an excellent white‐light under 254 nm UV irradiation.     

Photoconductive Hybrid Films via Directional Self‐Assembly of C60 on Aligned Carbon Nanotubes

Hybrid nanostructured materials can exhibit different properties than their constituent components, and can enable decoupled engineering of energy conversion and transport functions. Novel means of building hybrid assemblies of crystalline C₆₀ and carbon nanotubes (CNTs) are presented, wherein aligned CNT films direct the crystallization and orientation of C₆₀ rods from solution. In these hybrid films, the C₆₀ rods are oriented parallel to the direction of the CNTs throughout the thickness of the film. High‐resolution imaging shows that the crystals incorporate CNTs during growth, yet grazing‐incidence X‐ray diffraction (GIXD) shows that the crystal structure of the C₆₀ rods is not perturbed by the CNTs. Growth kinetics of the C₆₀ rods are enhanced 8‐fold on CNTs compared to bare Si, emphasizing the importance of the aligned, porous morphology of the CNT films as well as the selective surface interactions between C₆₀ and CNTs. Finally, it is shown how hybrid C₆₀–CNT films can be integrated electrically and employed as UV detectors with a high photoconductive gain and a responsivity of 10⁵ A W^?1 at low biases (± 0.5 V). The finding that CNTs can induce rapid, directional crystallization of molecules from solution may have broader implications to the science and applications of crystal growth, such as for inorganic nanocrystals, proteins, and synthetic polymers.     

Genetically Encoding Light-Responsive Protein-Polymers Using Translation Machinery for the Multi-Site Incorporation of Photo-Switchable Unnatural Amino Acids

A general and versatile technology to engineer light-responsive protein-based biomaterials can enable the manipulation and interrogation of proteins, pathways, and cells, and it will assist the design of “smart” light-responsive biomaterials. This study reports the evolution of chromosomal aminoacyl-tRNA synthetases (aaRSs) for azobenzene-bearing unnatural amino acids (uAAs) with up to ≈40-fold increased protein production and improved fidelity, as compared with a previously described aaRS. The evolved translation systems enable efficient and accurate incorporation of up to 10 instances of the various light-responsive uAAs in elastin-like polypeptides (ELPs). Azobenzene-containing ELPs are capable of isothermal, reversible, light-mediated soluble-to-insoluble phase transition, with up to a 12  °C difference in the ELP transition temperature upon cis-to-trans azobenzene isomerization. Furthermore, the incorporation of azobenzene-uAAs in ELP diblock-copolymers enables the creation of light-responsive self-assembled nanostructures. Finally, light-responsive resilin-inspired polymers are also generated by multi-site azobenzene-incorporation. The translation machinery evolved in this study can be used for the multi-site incorporation of azobenzene moieties at the polypeptide level and constitute a universal methodology for the design of light-responsive proteins and additional families of protein-based biomaterials with customized and tunable light-responsive behavior.     

Controlling the Self‐Assembly of Periodic Defect Patterns in Smectic Liquid Crystal Films with Electric Fields

Large‐area periodic defect patterns are produced in smectic A liquid crystals confined between rigid plate electrodes that impose conflicting parallel and normal anchoring conditions, inducing the formation of topological defects. Highly oriented stripe patterns are created in samples thinner than 2 μm due to self‐assembly of linear defect domains with period smaller than 4 μm, whereas hexagonal lattices of focal conic domains appear for thicker samples. The pattern type (1d/2d) and period can be controlled at the nematic–smectic phase transition by applying an electric field, which confines the defect domains to a thin surface layer with thickness comparable to the nematic coherence length. The pattern morphology persists in the smectic phase even after varying the field or switching it off. Bistable, non‐equilibrium patterns are stabilized by topological constraints of the smectic phase that hinder the rearrangement of defects in response to field variations.     

Electric Field‐Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin Films

A method of simultaneous field‐ and flow‐directed assembly of anisotropic titania (TiO₂) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (ν > ～25 kHz) and field strengths (E > 300 V cm^?1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1–10 µm is deposited on the substrate. The films exhibit a large birefringence (Δn ≈ 0.15) and high packing fraction (? = 0.75 ± 0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel–random–perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field‐directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process.     

Highly Conductive Organosilica Hybrid Films Prepared from a Liquid‐Crystal Perylene Bisimide Precursor

Significant anisotropic electrical conduction in organosilica films is achieved by long‐range orientation of electroactive perylene bisimide (PBI) moieties in the silica scaffold. A new PBI‐based organosilane precursor is designed with lyotropic liquid‐crystalline properties. The PBI precursor with triethoxysilylphenyl groups exhibits a hexagonal columnar phase in the presence of organic solvents. The lyotropic liquid‐crystalline behavior of the precursor enables the preparation of dip‐coated films consisting of uniaxially aligned columnar aggregates of the PBI precursor on the centimeter scale. The oriented structure is successfully fixed by in situ polycondensation, which yields insoluble, thermally stable PBI–silica hybrid films. The oriented organosilica films doped with hydrazine exhibit high electrical conductivities on the order of 10^?2 S cm^?1, which are at the highest level for organosilica materials, and are comparable to those of all‐organic PBI assemblies. Definite anisotropy of conductivities is also found for these films. The present results suggest that the induction of significant electrical properties in organic molecular assemblies is compatible with the structural stabilization by inorganic–organic hybridization.     

Interfacial Crystallization‐Driven Assembly of Conjugated Polymers/Quantum Dots into Coaxial Hybrid Nanowires: Elucidation of Conjugated Polymer Arrangements by Electron Tomography

A simple and practical “solution‐biphase method” allows the preparation of efficient charge‐transporting 1D nanocrystals with coaxial p–n junctions. It involves gradual diffusion of a top layer of poor solvent (acetonitrile) into a bottom layer of poly(3‐hexyl thiophene)‐b‐poly(2‐vinyl pyridine) (P3HT‐b‐P2VP) conjugated polymers (CPs) and CdSe quantum dots (QDs) dissolved in chloroform. Initial interfacial crystallization‐driven assembly of CPs results in the formation of seeds consisting of dimeric QDs transversely bridged by CPs. Coaxial CPs/QDs hybrid NWs are generated by 1D growth of QDs‐dimeric seeds, enabling tracing of the CPs‐crystallization process via the QDs. Thus, well‐arranged QDs along the longitudinal axis of the NWs infer highly crystalline CPs with edge‐on orientation, as confirmed by electron tomography, UV–vis spectroscopy, and grazing‐incidence wide‐angle X‐ray scattering. This high cristallinity as well as the increased length of the resulting hybrid NWs in solution and the corresponding crystallite size in as‐cast film represent a significant improvement compared to the conventional “one‐pot addition method”. Moreover, although randomly QDs‐attached hybrids of P3HT homopolymer are produced by the solution‐biphase method, branched aggregates with micrometer‐long NW arms are generated from the crystal seeds containing multiple growth facets without precipitate, despite acetonitrile being a nonsolvent.