Bicontinuous Structure Research Articles

Bicontinuous cubic phases in biological and artificial self-assembled systems.

Nature has created innumerable life forms with miraculous hierarchical structures and morphologies that are optimized for different life events through evolution over billions of years. Bicontinuous cubic structures, which are often described by triply periodic minimal surfaces (TPMSs) and their constant mean curvature (CMC)/parallel surface companions, are of special interest to various research fields because of their complex form with unique physical functionalities. This has prompted the scientific community to fully understand the formation, structure, and properties of these materials. In this review, we summarize and discuss the formation mechanism and relationships of the relevant biological structures and the artificial self-assembly systems. These structures can be formed through biological processes with amazing regulation across a great length scales; nevertheless, artificial construction normally produces the structure corresponding to the molecular size and shape. Notably, the block copolymeric system is considered to be an applicable and attractive model system for the study of biological systems due to their versatile design and rich phase behavior. Some of the phenomena found in these two systems are compared and discussed, and this information may provide new ideas for a comprehensive understanding of the relationship between molecular shape and resulting interface curvature and the self-assembly process in living organisms. We argue that the co-polymeric system may serve as a model to understand these biological systems and could encourage additional studies of artificial self-assembly and the creation of new functional materials.

A facile strategy towards developing amphiphobic polysulfone membrane with double Re-entrant structure for membrane distillation

Membrane surface wetting and fouling are still crucial issues in many separation processes such as membrane distillation (MD), especially when oil-contained feed solution was treated. To solve that problem, a facile synthesis strategy for amphiphobic polymeric membrane was successfully proposed in the current work. Via traditional non-solvent induced phase separation (NIPS) and subsequent sol-gel process, double re-entrant structure was ingeniously constructed; that is, the first level re-entrant structure was supplied by the bicontinuous inter-connected porous structure obtained through optimized phase separation parameters and the second level re-entrant structure was offered by the spherical and dimensionally different silicon dioxide (SiO2) nanoparticles which were spontaneously generated during sol-gel process. After cooperating with the fluorine-contained chemical coating, the resultant polysulfone (PSf) membrane with double re-entrant structure exhibited excellent and stable repellency performance to both water and organic liquid, even showing high hexadecane contact angle of 121° and hexane of 67°. Compared with solely hydrophobic membrane, the as-fabricated amphiphobic PSf membrane achieved long-term stable vapor flux and salt rejection in MD process even with the presence of surfactant sodium dodecyl sulfonate (SDS).

Dealloying Kinetics of AgAu Nanoparticles by In Situ Liquid-Cell Scanning Transmission Electron Microscopy.

Understanding the formation and evolution of bicontinuous nanoporous structure during dealloying has been one of the most challenging subjects of dealloying research. However, previous in situ investigations either suffer from insufficient spatial resolution (e.g., X-ray tomography) or lack morphology visualization and mass information (e.g., scanning tunneling microscopy). In this work, we report the kinetics of the whole course of dealloying by utilizing liquid-cell aberration-corrected scanning transmission electron microscopy. With Z-contrast imaging analysis, the in situ sub-nanoscale characterization reveals two new phenomena, an initial period of dealloying indicative of an initial length scale for bulk dealloying and a large volume shrinkage in a nanoscale alloy precursor. We explain the particle-size-dependent volume shrinkage with the formation of a dense shell and quantify the dependence with a simple geometric model. These insights into the mechanisms of dealloying will enable deliberate designs of nanoporous structures.

Crystal twinning of bicontinuous cubic structures.

Bicontinuous cubic structures in soft matter consist of two intertwining labyrinths separated by a partitioning layer. Combining experiments, numerical modelling and techniques in differential geometry, we investigate twinning defects in bicontinuous cubic structures. We first demonstrate that a twin boundary is most likely to occur at a plane that cuts the partitioning layer almost perpendicularly, so that the perturbation caused by twinning remains minimal. This principle can be used as a criterion to identify potential twin boundaries, as demonstrated through detailed investigations of mesoporous silica crystals characterized by diamond and gyroid surfaces. We then discuss that a twin boundary can result from a stacking fault in the arrangement of inter-lamellar attachments at an early stage of structure formation. It is further shown that enhanced curvature fluctuations near the twin boundary would cost energy because of geometrical frustration, which would be eased by a crystal distortion that is experimentally observed.

Tunable Periodically Ordered Mesoporosity in Palladium Membranes Enables Exceptional Enhancement of Intrinsic Electrocatalytic Activity for Formic Acid Oxidation

AbstractDeveloping superior electrocatalysts for formic acid oxidation (FAO) is the most crucial step in commercializing direct formic acid fuel cells. Herein, we electrodeposited palladium membranes with periodically ordered mesoporosity obtained by asymmetrically replicating the bicontinuous cubic phase structure of a lyotropic liquid‐crystal template. The Pd membrane with the largest periodicity and highest degree of order delivered up to 90.5 m2 g−1 of electrochemical active surface area and 3.34 A mg−1 electrocatalysis capability towards FAO, 3.8 and 7.8 times the values of the commercial Pd/C catalyst, respectively. By controlling the temperature and potential of the electrodeposition procedure, the periodicity area and order degree of the mesoporosity are highly tunable. These Pd membranes gave prototype formic acid fueled cells with 4.3 and 2.4 times the maximum current and power density of the commercial Pd/C catalyst.

Nanoparticles containing β-cyclodextrin potentially useful for the treatment of Niemann-Pick C.

β-Cyclodextrin (β-CD) is being considered a promising therapy for Niemann-Pick C (NPC) disease because of its ability to mobilise the entrapped cholesterol from lysosomes, however, a major limitation is its inability to cross the blood-brain barrier (BBB) and address the central nervous system (CNS) manifestations of the disease. Considering this, we aimed to design nanoparticles able to cross the BBB and deliver β-CD into the CNS lysosomes. The physicochemical characteristics of β-CD-loaded nanoparticles were evaluated by dynamic light scattering, small-angle X-ray scattering, and cryogenic transmission electron microscopy. The in vitro analyses were performed with NPC dermal fibroblasts and the β-CD-loaded nanoparticles were tracked in vivo. The nanoparticles showed a mean diameter around 120 nm with a disordered bicontinuous inner structure. The nanoparticles did not cause decrease in cell viability, impairment in the antioxidant enzymes activity, damage to biomolecules or release of reactive species in NPC dermal fibroblasts; also, they did not induce genotoxicity or alter the mitochondrial function in healthy fibroblasts. The β-CD-loaded nanoparticles were taken up by lysosomes reducing the cholesterol accumulated in NPC fibroblasts and reached the CNS of mice more intensely than other organs, demonstrating advantages compared to the free β-CD. The results demonstrated the potential of the β-CD-loaded nanoparticles in reducing the brain impairment of NPC.

Cryopolymerization enables anisotropic polyaniline hybrid hydrogels with superelasticity and highly deformation-tolerant electrochemical energy storage

The development of energy storage devices that can endure large and complex deformations is central to emerging wearable electronics. Hydrogels made from conducting polymers give rise to a promising integration of high conductivity and versatility in processing. However, the emergence of conducting polymer hydrogels with a desirable network structure cannot be readily achieved using conventional polymerization methods. Here we present a cryopolymerization strategy for preparing an intrinsically stretchable, compressible and bendable anisotropic polyvinyl alcohol/polyaniline hydrogel with a complete recovery of 100% stretching strain, 50% compressing strain and fully bending. Due to its high mechanical strength, superelastic properties and bi-continuous phase structure, the as-obtained anisotropic polyvinyl alcohol/polyaniline hydrogel can work as a stretching/compressing/bending electrode, maintaining its stable output under complex deformations for an all-solid-state supercapacitor. In particular, it achieves an extremely high energy density of 27.5 W h kg−1, which is among that of state-of-the-art stretchable supercapacitors.

Structure evolution of bio-based PLA/ENR thermoplastic vulcanizates during dynamic vulcanization processing

The thermoplastic vulcanizates (TPVs) of Polylactide (PLA)/Epoxidized natural rubber (ENR) were prepared by dynamic vulcanization technology. The processing torque, crosslink density, morphology of PLA/ENR blends, and PLA's molecular weight during the processing were investigated by HAAKE rheometer, swelling measurement, scanning electron microscopy (SEM), and gel permeation chromatography (GPC). It was found that the vulcanization of ENR completed at the turning point after torque peak. After the turning point, the torque and crosslink density decreased with the processing time increasing. Moreover, the morphology of PLA/ENR blends showed bi-continuous structure during the dynamic vulcanization processing, and the phase size of PLA/ENR was increased with processing time and temperature. GPC results showed PLA degradation mainly happened after torque turning point. Thermal gravimetric analysis (TGA) results indicated that some parts of PLA would graft on ENR during processing, and the higher the processing temperature, the more the PLA was grafted.

A polyimide-pyrolyzed carbon waste approach for the scalable and controlled electrochemical preparation of size-tunable graphene.

Carbon materials are widely used in numerous fields, thus changing our lives. With the increasing consumption of carbon-based products, the disposal of consequent wastes has become a challenge due to their inert nature, which is hard to degrade, burn, or melt. Here, a recyclable strategy is proposed to deal with the explosive growth of carbon wastes. Through a fast and clean electrochemical method, carbon wastes are converted into functional building blocks of high value, such as graphene and graphene quantum dots (GQDs). For typical polyimide-pyrolyzed carbon (PPC), we establish the relationship between the chemical structure of raw materials and the characteristics of graphene products, including size and yield. The size-tunable graphene ranging from 3 nm to tens of micrometers is prepared by tuning the sp3/sp2 carbon ratio of PPC from 0.5 to 0 at adjustable temperatures (800 °C-2800 °C). Significantly, PPC with a bicontinuous structure (comprising sp2 and sp3) was efficiently cut into GQDs in 2 h with a high yield of 98%. Our protocol offers great potential for the scale-up preparations and applications of GQDs. Besides, we demonstrate that the GQDs performed well as dispersants to disperse hydrophobic carbon nanotubes (0.6 mg mL-1) in water and improved the gravimetric capacitance of graphene-based supercapacitors by 79.4% with 3% GQDs added as nano-fillers.

Quo vadis biophotonics? Wearing serendipity and slow science as a badge of pride, and embracing biology.

This article is a reflection on the themes of the Faraday Discussion meeting on 'Biological and bio-inspired optics' held from 20 to 22 July 2020. It is a personal perspective on the nature of this field as a broad and interdisciplinary field that has led to a sound understanding of the material properties of biological nanostructured and optical materials. The article describes how the nature of the field and the themes of the conference are reflected in particular in work on the 3D bicontinuous biophotonic nanostructures known as single gyroids and in bicontinuous structures more broadly. Such single gyroid materials are found for example in the butterfly Thecla opisena, where the questions of biophotonic response, of bio-inspired optics, of the relationship between structure and function, and of the relationship between natural and synthetic realisations are closely interlinked. This multitude of facets of research on single gyroid structures reflects the beauty of the broader field of biophotonics, namely as a field that lives through embracing the serendipitous discovery of the biophotonic marvels that nature offers to us as seeds for in-depth analysis and understanding. The meandering nature of its discoveries, and the need to accept the slowness that comes from exploration of intellectually new or foreign territory, mean that the field shares some traits with biological evolution itself. Looking into the future, I consider that a closer engagement with living tissue and with the biological questions of function and formation, rather than with the materials science of biological materials, will help ensure the continuing great success of this field.

Elegant design of carbon nanotube foams with double continuous structure for metamaterials in a broad frequency range

A CNT foam-based metamaterial was successfully designed with a bicontinuous phase structure and pressure-adjustable negative permittivitty and permeability.

Bicontinuous Nanoporous Design Induced Homogenization of Strain Localization in Metallic Glasses

Bi-continuous nano-porous metallic glasses (MG) synergize the outstanding properties of MGs and open-cell nano-porous materials. The low-density and high-specific-surface-area of bi-continuous nano-porous structures have the potential to enhance the applicability of MGs in catalysis, sensors, and lightweight structural designs. Here, we report molecular dynamics simulations of tensile loading deformation and failure of bi-continuous nano-porous Cu64Zr36 MG with 55% porosity and 4.4 nm ligament size. Results indicate an anomalous mechanical behavior featuring delocalized plastic deformation preceding ductile failure. The deformation follows two mechanisms: i) Necking of ligaments aligned with the loading direction and ii) progressive alignment of randomly oriented ligaments. Failure occurs at 0.16 strain, following successive necking and rupture events. This work indicates that a bi-continuous nano-porous design is able to effectively delocalize strain localization in a MG due to a combination of size effect on the ductility of MGs resulting in nano-ligaments necking and progressive asynchronous alignment of ligaments.

Numerical Investigation of Damage Accumulation and Failure Processes in Random Porous Bicontinuous Media

Heterogeneous materials with bicontinuous foam-like structure were investigated. The aim of the work was to create models of failure of representative volume elements (RVEs) of such materials and to reveal the dependencies of the character of failure processes on the structural morphology peculiarities. To create models of RVEs with open-cell interpenetrating structures, approaches based on the analytical determination of surfaces separating the two phases were used. Mechanical modeling was performed with the finite element analysis using properties degradation and element removal techniques. The modelling results obtained for high-dense aluminum foam materials are presented. The influence of the size of representative volume element and its volume fraction on the fracture process has been studied.

Nanoporous metal based composites: Giving polymers strength and making metals move

One of the outstanding characteristics of electroactive polymers is their large strain response under electrical stimulus, which can be utilized for actuation applications. However, for extensive mechanical use in electro-mechanical systems, they lack the necessary strength and stiffness. To improve polymer actuator strength, the incorporation of a metal reinforcement phase has been proposed: by forming an inter-penetrating metal-polymer composite, a much stronger actuator can be created. This work focuses on nanoporous metals as the metal reinforcement: they have impressive mechanical properties, while simultaneously allowing almost unhindered ion flow due to their characteristic bi-continuous structure. To explore the effects of the metal volume fraction on the ion transport, deformation and stress response of this composite, this work investigates the chemo-electro-mechanical behaviour of a nanoporous metal-polymer composite material using finite element simulations on representative volume elements at various volume fractions.

Structurally ordered nanoporous Pt–Co alloys with enhanced mechanical behaviors in tension

Abstract An ordered bimetallic nanoporous structure might be preferable and promising for catalytic applications due to the decreased Pt loading and the enhanced stability. Understanding the mechanical behaviors is the prerequisite for enhancing and prolonging the durability performance of catalysts. Herein, nanoporous (NP) Pt–Co alloys with three–dimensional stochastic bi–continuous structures are created by simulating the spinodal evolution. Molecular dynamics (MD) simulations have been utilized to research the mechanical behaviors of structurally ordered nanoporous Pt–Co alloys ( NP - Pt 3 Co , NP - PtCo 3 and NP - PtCo ) under uniaxial tension. The mechanical properties of three tested nanoporous Pt–Co alloys are significantly enhanced compared with NP–Pt, and NP - Pt 3 Co behaves with the superior mechanical properties due to its unique atomic arrangements. The dominating plastic deformation in the ligaments of nanoporous Pt–Co alloys is the axial yielding, and materials primarily fail through plastic necking and rupture of those ligaments in the loading direction, similar to that of NP–Au. Not only the modulus but also the strength scales a linear or exponential relation with relative density. The present results will provide insights for the mechanical optimization of nanoporous alloys as well as a new design strategy for more stable catalysts. Subjectareas material science, computational material.

An efficient 3D ordered mesoporous Cu sphere array electrocatalyst for carbon dioxide electrochemical reduction

The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions. However, this solution has been challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays, which is fabricated by a dual template method using a poly methyl methacrylate (PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal. Therefore, the well-ordered 3D interconnected bi-continuous mesopores structure has advantages of abundant exposed catalytically active sites, efficient mass transport, and high electrical conductivity, which result in excellent electrocatalytic CO2RR performance. The prepared 3D ordered mesoporous Cu sphere array (3D-OMCuSA) exhibits a low onset potential of -0.4 V at a 1 mA cm−2 electrode current density, a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate. These distinct features of 3D-OMCuSA render it a promising method for the further development of advanced electrocatalytic materials for CO2 reduction.

Effect of mixed diluents during thermally induced phase separation process on structures and performances of hollow fiber membranes prepared using triple-orifice spinneret

In this study, polyvinylidene fluoride hollow fiber membranes were prepared using a triple-orifice spinneret in thermally induced phase separation. A solvent, propylene carbonate (PC), was extruded through the outermost layer of the spinneret. Through the use of this method, all the membranes were developed an entirely porous surface with similar pore size and porosity. Using mixed diluents with different concentrations of diphenyl carbonate and PC, the membrane bulk structures were controlled from an entirely bicontinuous network, a combination of bicontinuous and spherulitic structures, to an entirely spherulitic structure. The tailored bulk structures showed significant effects on the permeability, rejection, and mechanical strength of the membrane. Furthermore, the membrane sub-layer structure was modified to form different types from the composite-like structure of the combination of the spherulites and bicontinuous network to entirely spherulites, which controlled the membrane permeation stability within an extensive range of 6% to nearly 100%. A change in the polymeric dope solution phase diagram, as well as the interfacial behaviors of the polymeric dope solution and extruded PC, played important roles in appropriately tailoring membrane structures and performances. These novel and solid findings regarding the connections between structures and performances provide an advisable venue for the design of hollow fiber membranes with satisfactory performances.

Water redistribution determined by time domain NMR explains rheological properties of dense fibrous protein blends at high temperature

Blends of different plant proteins can form excellent basis for meat analogues by subjecting those to shear and heating. We here want to obtain more information of the internal structure of pea protein-gluten and soy protein-gluten blends, by using the polymer blending law to explain rheological responses. For this polymer blending law the water distribution over the two phases is the blend was obtained with time domain 1H NMR measurements using the NMR measurements of individual protein phases and on the blend. By matching the relaxation rate (R2) of the individual phases with those of the blend, the water distribution over the two phases could be obtained. Water is preferentially taken up by the soy or pea protein phase leaving less water for gluten, which effect strongly changes the volume fractions of the phases. Rheological properties of the separate phases as function of their hydration resulted in higher apparent modulus for the wheat gluten phase, and a lower one for the pea and soy protein phase. From the results, it was concluded that both blends show signs of a bi-continuous morphology. The SPI-WG blend showed an intermediate value between bi-continuous and SPI continuous. PPI-WG at lower temperatures showed a bi-continuous structure, while at higher processing temperatures and time was probably WG continuous.

Biobased PLA/NR-PMMA TPV with balanced stiffness-toughness: In-situ interfacial compatibilization, performance and toughening model

Using rubber to toughen polylactide (PLA) is always accompanied by the sharp reduction in stiffness. Herein, PLA/poly (methyl methacrylate) grafted natural rubber (NR-PMMA) thermoplastic vulcanizates (TPVs) with balanced stiffness-toughness were fabricated. With the addition of 40 wt % NR-PMMA, the impact strength and tensile toughness of PLA/NR-PMMA TPV significantly improved to about 102.7 kJ/m2 and 66.1 MJ/m3, respectively, compared with those of 2.7 kJ/m2 and 2.4 MJ/m3 for the pure PLA. Meanwhile, the yielding stress was maintained at 34.5 MPa. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of in-situ interfacial compatibilization between PLA and rubber phases. Both tensile and impact toughening mechanism were studied and deduced as considerable energy dissipation provided by the continuous rubber phase. Instrumented notched impact tests demonstrated that the energy dissipating in crack propagation process contributed to the main part of impact toughness. In addition, a novel toughening model based on bicontinuous structure was incorporated, which showed good applicability in predicting the impact strength of PLA/NR-PMMA TPVs.

Fabrication of bicontinuous double networks as thermal and pH stimuli responsive drug carriers for on-demand release.

The fabrication, via a two steps approach, of a novel bicontinuous Double Network (BCDN) material is reported. We first use a bicontinuous emulsion as template to obtain a poly(butyl acrylate) (PBA) and poly(acrylic acid) (PAA) bicontinuous amphiphilic material. The material is then swollen with the precursor of a second hydrophilic polymer (PNIPAM, poly(N-isopropylacrylamide)). After polymerization of these precursors, the two responsive polymers, PNIPAM and PAA, form a double-network within a bicontinuous templated material, i.e. a bicontinuous double network (BCDN) material. The advantages of using such unique and complex double network architecture are manifold. PBA increases the mechanical properties of the hydrogel all together with the hydrophilic double network that also decouples the pH and temperature responsiveness. Among different possible applications, we tested this responsive hydrogels for its biomedical application. It can be used as pH and temperature sensitive devices for on-demand drug delivery. In addition, the release of a drug confined in the amphiphilic bicontinuous structure follows different kinetics profiles, depending on pH and temperature. This last result indicates that it is possible to control and regulate the release of an encapsulated drug according to the fluctuations of physiological conditions.