Bicontinuous Structure Research Articles

Preparation and Properties of Poly(butylene adipate-co-terephthalate)/thermoplastic Hydroxypropyl Starch Composite Films Reinforced with Nano-Silica.

The use of biodegradable plastics is gradually increasing, but its expensive cost limits promotion. In this study, poly(butylene adipate-co-terephthalate)/thermoplastic hydroxypropyl starch reinforced with nano-silica (PBAT/TPHSg-SiO2) composite films with high hydroxypropyl starch content were prepared in a two-step process. The effect of reinforced thermoplastic hydroxypropyl starch on the mechanical, thermal, processing properties, and micromorphology of the composite films was investigated. The results showed that the tensile strength of the composite films was significantly improved by the addition of nano-silica, with 35% increase in horizontal tensile strength and 21% increase in vertical tensile strength after the addition of 4 phr of nano-silica. When the content of thermoplastic hydroxypropyl starch reinforced with nano-silica (TPHSg-4SiO2) is 40%, the horizontal and vertical tensile strengths of the films are 9.82 and 12.09 MPa, respectively, and the elongation at break of the films is over 500%. Electron micrographs show that TPHSg-4SiO2 is better homogeneously dispersed in the PBAT and exhibits a bi-continuous phase structure at a TPHSg-4SiO2 content of 40%. In this study, the blowing PBAT/TPHSg-4SiO2 composite films effectively reduce the cost and still show better mechanical properties, which are suitable for packaging applications.

Nanoporous Amorphous Carbon with Exceptional Ultra-High Strength.

Nanoporous materials show a promising combination of mechanical properties in terms of their relative density; while there are numerous studies based on metallic nanoporous materials, here we focus on amorphous carbon with a bicontinuous nanoporous structure as an alternative to control the mechanical properties for the function of filament composition.Using atomistic simulations, we study the mechanical response of nanoporous amorphous carbon with 50% porosity, with sp3 content ranging from 10% to 50%. Our results show an unusually high strength between 10 and 20 GPa as a function of the %sp3 content. We present an analytical analysis derived from the Gibson-Ashby model for porous solids, and from the He and Thorpe theory for covalent solids to describe Young's modulus and yield strength scaling laws extremely well, revealing also that the high strength is mainly due to the presence of sp3 bonding. Alternatively, we also find two distinct fracture modes: for low %sp3 samples, we observe a ductile-type behavior, while high %sp3 leads to brittle-type behavior due to high high shear strain clusters driving the carbon bond breaking that finally promotes the filament fracture. All in all, nanoporous amorphous carbon with bicontinuous structure is presented as a lightweight material with a tunable elasto-plastic response in terms of porosity and sp3 bonding, resulting in a material with a broad range of possible combinations of mechanical properties.

Fabrication and Evaluation of Filtration Membranes from Industrial Polymer Waste

Polyvinylidene fluoride (PVDF) polymers are known for their diverse range of industrial applications and are considered important raw materials for membrane manufacturing. In view of circularity and resource efficiency, the present work mainly deals with the reusability of waste polymer 'gels' produced during the manufacturing of PVDF membranes. Herein, solidified PVDF gels were first prepared from polymer solutions as model waste gels, which were then subsequently used to prepare membranes via the phase inversion process. The structural analysis of fabricated membranes confirmed the retention of molecular integrity even after reprocessing, whereas the morphological analysis showed a symmetric bi-continuous porous structure. The filtration performance of membranes fabricated from waste gels was studied in a crossflow assembly. The results demonstrate the feasibility of gel-derived membranes as potential microfiltration membranes exhibiting a pure water flux of 478 LMH with a mean pore size of ~0.2 µm. To further evaluate industrial applicability, the performance of the membranes was tested in the clarification of industrial wastewater, and the membranes showed good recyclability with about 52% flux recovery. The performance of gel-derived membranes thus demonstrates the recycling of waste polymer gels for improving the sustainability of membrane fabrication processes.

Fast formation of strong symmetric poly (vinylidene fluoride) membranes via a modified VIPS method

BackgroundPolymer membranes for microfiltration and membrane distillation should be skinless and symmetric with a bi-continuous structure. To effectively eliminate the inherently formed skin layer and macrovoids in the membrane, proper modifications of preparation parameters are proposed. MethodsSkinless microporous poly(vinylidene fluoride) (PVDF) membranes with a uniform bi-continuous structure were fabricated through phase inversion processes that combine vapor-induced phase separation (40 °C and 70% relative humidity) and non-isothermal immersion precipitation (22 °C) with casting dopes consisting of triethyl phosphate (TEP), PVDF, and a small amount of glycerol, a nonsolvent. Significant findingsIntroduction of glycerol to the dope solution induces a rapid polymer crystallization upon exposure to water vapor. Experimental results demonstrate that a skinless microporous membrane can be obtained with a short vapor exposure time of 1.5 min. Additionally, the synthesized membrane possesses ideal filtration properties, including high hydrophobicity (contact angle = 113° for both surfaces), high porosity (83%), adequate strength (2.4 N/mm2), and suitable pore size (0.12 μm). This membrane also exhibits superb rejection capability (99%) and high permeation flux (450 LMH) for filtration of poly(methyl methacrylate) particles with an average size of 0.15 μm..

Programmed Self-Assembly of Single Colloidal Gyroids for Chiral Photonic Crystals.

Gyroid structures are of extensive interest because they provide a rich platform for chiroptics as well as topological photonics. While the double-gyroid morphology as a bicontinuous structure is not uncommon in self-assembled soft materials, direct self-assembly of single-network gyroids has proven elusive. Here, an enantiomorphic pair of single-gyroid crystals comprising colloidal spheres is presented, and two distinct routes are demonstrated for programmed self-assembly of each single colloidal gyroid enantiomorph from rationally designed patchy spheres. The designer colloidal patchy spheres, which closely hew to their synthetic feasibility, are chiral, having either two staggered rectangular patches at opposite poles or four circular patches arranged in a well-defined geometry. The single colloidal gyroid, as well as its inverse structure, is shown to support a wide complete photonic bandgap in addition to exhibiting rich chiroptical properties, making them attractive chiral photonic crystals. The versatility of this single colloidal gyroid, the bottom-up routes devised here in silico, and the robustness of the design space for the chiral colloidal patchy spheres together make a strong case for single colloidal gyroids to supersede colloidal diamond, as a target for programmed self-assembly, in the quest for a photonic crystals operating at opticalfrequencies.

Dual-Ion Co-intercalation Mechanism on a Na2V6O16·3H2O Cathode with a Commercial-Level Mass Loading for Aqueous Zinc-Ion Batteries with High Areal Capacity.

A proton (H+) and zinc ion (Zn2+) co-insertion model is put forward in this study to elucidate the capacity origin of an aqueous zinc ion battery (ZIB) based on a heavily loaded (∼15 mg cm-2) cathode, which consists of Na2V6O16·3H2O (NVO) embedded particularly in the macropores of activated carbon cloth (ACC), coupled with a highly stable Zn/In anode. The confinement effect of these porous channels not only prevents the detachment of NVO from ACC but also well mitigates its volume change resulting from H+ and Zn2+ co-intercalation, which collectively render the stability of NVO/ACC markedly enhanced. Moreover, the bicontinuous structure of NVO/ACC, as a result of the self-interlacing of intrapore NVO, which is first engineered into the nanobelts, and their interlocking with the carbon fibers of ACC, simultaneously giving rise to a solid and a holey framework, is favorable to the electron and ion transport throughout the entire electrode. The synergistic effect of such facile charge transfer kinetics and the high packing density of NVO in the cathode endows ZIBs with not only a good rate performance but also an exceptional areal capacity amounting to 4.6 mAh cm-2, far surpassing those reported for additional vanadium-based counterparts reported in the literature.

Novel Single-Ion Conducting Gel Polymer Electrolyte with Honeycomb-Like Morphology Prepared Using Brush Copolymer for Lithium-Ion Battery Application

In this work, a facile and accurate method is reported for the delocalization of negative charge on fluorinated polymers to obtain high-performance single-ion conducting polymer electrolytes (SICPs) based on brush copolymers with simultaneous high ionic conductivity and tLi+. The poly(styrene sulfonate) (PSSA) single ion-conducting moieties were grafted-from C–F linkages to the fluorinated polymer’s backbone via the atom transfer radical polymerization method. The chemical structure characterization of the synthesized brush copolymers via 1H-NMR and thermal gravimetric analyses (TGA) confirmed 25% grafting of PSSA to the poly(vinylidene fluoride) backbone. In continue, the pristine and single-ion fluorinated polymer membranes with bi-continuous honeycomb-like morphology structures were prepared via the vapor-induced phase inversion (VIPS) method. After immersing in a liquid electrolyte, the prepared SICP demonstrated promising ionic conductivity (σ), t Li+ , and electrochemical stability of 1.9 × 10−3 Scm−1, 0.82, and 5.2 V (vs Li+/Li), respectively. The assembled Li/SICP/LiMn2O4 half-cells revealed an improved discharge capacity of 168 mA hg−1 at 0.1C. The charge-discharge studies revealed that the ohmic-resistance and polarization resistance of fluorinated polymer electrolytes could be decreased by the effect of PSSA-grafted moieties. The results of this work confirmed the promising capability of these new SICPs for high-safety LIBs.

Preparation and characterization of light weight aluminum matrix syntactic foams with high energy absorbing capacity

Aluminum matrix syntactic foams (AMSFs) with low density are widely utilized in the field of impact resistance owing to their high energy absorbing properties. In present study, to further lower the density and improve the energy absorption of AMSFs, a low-temperature micro-pressure infiltration was utilized to avoid destroying the hollow structure and a bi-continuous structure was designed to increase the energy absorbing interface and improve the deformation behavior. Results show that the hollow sphere content was up to 65% and a breakage rate was below 4% in the composites. Meanwhile, the composites displayed a rather low density of 1.23–1.41 g cm−3, a high compressive strength of 83.96–243.31 MPa, and an excellent energy absorbing capacity of 38.07–99.51 MJ m−3 under quasi-static loading, which outperforms the most advanced AMSFs as reported in the literatures. With the increase of strain rate, the composites showed higher plateau stress and energy absorbing capacity under dynamic loading. The energy was absorbed by shear deformation of cenospheres and interfacial tearing between cenospheres and aluminum matrix. A unique “fracture ring” was observed in bi-continuous structure preventing crack growth.

Rheological properties and microstructure of thermodynamically stable microemulsions as factors influencing the release rate of liposoluble vitamins

Microemulsions (ME) are stable nano-sized emulsions that constitute one of the most effective ways to incorporate lipophilic active compounds into water-based food matrices. Great stability, colloidal domain droplets, and optical isotropy are some of the advantages of ME. The present work analyzed the influence of rheological behavior and microstructural characteristics of food microemulsions on the release rate of lipophilic vitamins E and D. A fluid ME was compared to a ME with a higher dispersed phase content and a bicontinuous structure (gel-ME). Additionally, carboxymethyl cellulose (CMC) was added to fluid ME (3.5 and 10 g/100 g), obtaining systems with different apparent viscosities and microstructure. The percentage of released vitamins was determined by HPLC, and mathematically modeled. All ME were characterized using TEM microscopy FTIR, rheological and viscoelastic analysis. Fluid and gel-ME reached higher percentages of vitamin release in a very fast manner, while systems containing CMC showed a matrix-driven nature of the release. Those systems with similar zero-shear viscosity and different microstructure exhibited significantly different viscoelastic behavior. Microemulsions with CMC exhibited a viscoelastic solid type behavior with G’ > G’’. Mechanical spectra were satisfactorily fitted with the Generalized Maxwell model and relaxation time spectra were determined. In the quiescent state, gel-ME exhibited a higher plateau modulus than those containing large amount of thickener in the continuous phase. The relaxation time behavior of the structure could explain the kinetic release of liposoluble vitamins from the inner lipid phase of the microemulsions.

Enhanced compressive mechanical properties in stochastic bicontinuous porous structures

Inspired by the morphology of dealloyed nanoporous metals, we derive a novel open-celled porous structure with stochastic bicontinuous cell. The polymeric porous specimens are fabricated by additive manufacturing (AM), and the compressive mechanical properties and energy absorption capacity are explored experimentally. Results show that Young’s modulus, yield stress, plateau stress, and energy absorption characteristics are monotonically increasing with the relative density, obeying the Gibson-Ashby power correlation. Due to more defects generated in the specimen with smaller ligament diameter during AM, there is a significant decrease in Young’s modulus and a slight decrease in yield stress with the decrease of ligament diameter, which is opposite to the size effect in nanomaterials. Attributing to the bending and yielding deformation of ligaments, the stochastic bicontinuous porous solids show an enhanced energy absorption capacity. The ligament morphological structure has shown to be an additional factor affecting the mechanical responses of porous solids, and might magnify its sensitivity to structural characteristics. This study provides valuable idea and guidance for designing efficient open-celled porous structures in the promising application of energy absorption.

Nanoscale Structure–Property Relations in Self-Regulated Polymer-Grafted Nanoparticle Composite Structures

Using a model system of poly(methyl methacrylate)-grafted silica nanoparticles (PMMA-NP) and poly(styrene-ran-acrylonitrile) (SAN), we generate unique polymer nanocomposite (PNC) morphologies by balancing the degree of surface enrichment, phase separation, and wetting within the films. Depending on the annealing temperature and time, thin films undergo different stages of phase evolution, resulting in homogeneously dispersed systems at low temperatures, enriched PMMA-NP layers at the PNC interfaces at intermediate temperatures, and three-dimensional bicontinuous structures of PMMA-NP pillars sandwiched between two PMMA-NP wetting layers at high temperatures. Using a combination of atomic force microscopy (AFM), AFM nanoindentation, contact angle goniometry, and optical microscopy, we show that these self-regulated structures lead to nanocomposites with increased elastic modulus, hardness, and thermal stability compared to analogous PMMA/SAN blends. These studies demonstrate the ability to reliably control the size and spatial correlations of both the surface-enriched and phase-separated nanocomposite microstructures, which have attractive technological applications where properties such as wettability, toughness, and wear resistance are important. In addition, these morphologies lend themselves to substantially broader applications, including: (1) structural color applications, (2) tuning optical adsorption, and (3) barrier coatings.

Impact-Protective Bicontinuous Hydrogel/Ultrahigh-Molecular Weight Polyethylene Fabric Composite with Multiscale Energy Dissipation Structures for Soft Body Armor.

Soft body armor greatly improves the comfort and security of the wearers. Although laminates based on high-performance fabrics have been adopted, it remains an enormous challenge to develop fabric laminates having flexibility, low bulge deformation, and ballistic protection capability simultaneously. Herein, we report a bullet-proof bicontinuous hydrogel (BH)/ultrahigh-molecular weight polyethylene fabric (UPF) composite. The presence of the BH significantly improves the impact resistance performance of the UPF, without compromising its flexibility. In specific, the multiscale energy dissipation structures composed of hydrogen bond associations in the chain scale, bicontinuous phase structures in the nanoscale, and fibers in the microscale are broken to dissipate energy. As a result, the impact energy of the bullet is greatly absorbed and the bulge height of the composites is significantly reduced in contrast to the neat UPF laminates. This study indicates that the flexible BH-UPF composites with multiscale energy dissipation structures have a promising application in soft body armor.

Development and characterization of food-grade bigel system for 3D printing applications: Role of oleogel/hydrogel ratios and emulsifiers

This study objected to widen the knowledge and applications of bigels by constructing food bigels for 3D printing. A serious of bigels were developed by incorporating a candelilla wax-based oleogel into a gelatin hydrogel at different oleogel/hydrogel ratios of 3:7, 5:5, and 7:3 under the presence of different emulsifiers (PGPR, monoglycerides and lecithin). And the influence of different oleogel/hydrogel ratios and emulsifiers on the physical properties and 3D printability of resulting bigels were studied. Bigels containing monoglycerides or lecithin could form homogenous, stable gel system with bicontinuous emulsion structure. Microstructure analysis found that PGPR could disturbed the crystalline process of candelilla wax resulting in weak mechanical strength of resulting oleogel and phase separation of bigels. These bigels exhibited shear-thinning behavior and improved mechanical properties (apparent viscosity, storage modulus, hardness, etc.) compared to pure oleogel and pure hydrogel. Bigels containing monoglyceride with oleogel/hydrogel ratio of 7:3 exhibited suitable mechanical properties for 3D printing. The results from this study indicated that 3D printable bigels could be obtained by combining candelilla wax (organogelators) with gelatin (hydrogelator), and the physical, printing properties of these bigels could be tailored by adjusting oleogel/hydrogel ratios and using different emulsifiers.

Formation of a nanoporous layer on the surface of silver and copper by dealloying of thermal diffusion coatings Me5Zn8 (Me=Ag, Cu) in a deep eutectic solvent

ABSTRACT Selective anodic dissolution of pre-galvanized surfaces was used to obtain nano-porous layers of approximately 10 microns thick on copper and silver specimens. To achieve single-phase homogeneous thermal diffusion layers of Cu5Zn8 and Ag5Zn8, we used a zinc plating process carried out in molten eutectic (KCl–NaCl–ZnCl2) at Т = 370°С. Dealloying of these coatings in a deep eutectic solvent (choline chloride/urea + 0.1 mol/l ZnCl2) at T = 133°C produced a typical bi-continuous structure of pores and ligaments (100 nm) on the surface of the silver and the copper.

Effect of Polydopamine Coating of Cellulose Nanocrystals on Performance of PCL/PLA Bio-Nanocomposites.

In bio-nanocomposites with a poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) matrix with neat and polydopamine (PDA)-coated cellulose nanocrystals (CNCd), the use of different mixing protocols with masterbatches prepared by solution casting led to marked variation of localization, as well as reinforcing and structure-directing effects, of cellulose nanocrystals (CNC). The most balanced mechanical properties were found with an 80/20 PLA/PCL ratio, and complex PCL/CNC structures were formed. In the nanocomposites with a bicontinuous structure (60/40 and 40/60 PLA/PCL ratios), pre-blending the CNC and CNCd/PLA caused a marked increase in the continuity of mechanically stronger PLA and an improvement in related parameters of the system. On the other hand, improved continuity of the PCL phase when using a PCL masterbatch may lead to the reduction in or elimination of reinforcing effects. The PDA coating of CNC significantly changed its behavior. In particular, a higher affinity to PCL and ordering of PLA led to dissimilar structures and interface transformations, while also having antagonistic effects on mechanical properties. The negligible differences in bulk crystallinity indicate that alteration of mechanical properties may have originated from differences in crystallinity at the interface, also influenced by presence of CNC in this area. The complex effect of CNC on bio-nanocomposites, including the potential of PDA coating to increase thermal stability, is worthy of further study.

Constructing Sub 10 nm Scale Interfused TiO2/SiOx Bicontinuous Hybrid with Mutual-Stabilizing Effect for Lithium Storage

TiO2 has been considered as a promising intercalation lithium-ion-battery (LIB) anode material owing to its robust cyclability. However, it suffers from low capacity. Herein, we construct a sub 10 nm scale interfused TiO2/SiOx hybrid with a bicontinuous structure, in which bridged TiO2 nanoparticles (over 80 wt %) are densely packed within a wormlike SiOx network, through the simple oxidation of MAX Ti3SiC2 ceramic. State-of-the-art in situ microscopy characterization unravels a "mutual-stabilizing" effect from the interfused TiO2/SiOx hybrid upon lithiation. That is to say, the two interpenetrated active components restrain the volume expansion of each other with the stress being relieved through abundant interfaces. Meanwhile, the stress generated from one phase functioned as the compressive force on the other phase and vice versa, offsetting the overall volume effect and synergistically reinforcing the structure integrity. Benefiting from the "mutual-stabilizing" effect, the TiO2/SiOx composite manifests a high and stable specific capacity (∼671 mAh g-1 after 580 cycles at 0.1 A g-1) with a low volume expansion of ∼14% even in an extended potential window of 0.01-3.0 V (vs Li+/Li). The concept of mutual-stabilizing effect, in principle, applies to a wide class of interfused bicontinuous hybrids, providing insight into the design of LIB anode materials with high capacity and longevity.

Fabrication and Evaluation of Multiwalled Carbon Nanotube-Containing Bijels and Bijels-Derived Porous Nanocomposites

Structures having continuous porous networks are of great interest for applications in areas such as separation, energy storage, and tissue engineering. Bicontinuous interfacially jammed emulsion gels ("bijels") have been actively investigated as templates for fabricating useful structures for such applications. However, the fabrication of bijels-templated porous nanocomposites incorporated with reinforcing or functional nanoparticles (or nanofibers) to provide specific, targeted functions is still a challenge, stemming from the difficulties of fabricating functional nanoparticle-containing bijels. In this study, bijels-derived porous nanocomposites incorporated with multiwalled carbon nanotubes (MWCNTs), which possessed interconnected channels inside the structures, were made via a facile phase inversion technique for bijels fabrication. For the composite manufacture, in the first step of bijels fabrication, MWCNT adsorption into the oil phase of bijels was observed. It was revealed that MWCNTs were physically absorbed into the oil-rich phase without disrupting the bicontinuous structure of bijels. The successful fabrication of non-crosslinked and crosslinked porous structures containing MWCNTs was evidenced through imaging by confocal laser scanning microscopy and scanning electron microscopy, respectively. For potential controlled release applications, an anticancer drug, doxorubicin hydrochloride (DOX), was incorporated into bijels-derived structures and nanocomposites. The in vitro DOX release profiles from drug delivery systems based on bijels-derived MWCNT-containing nanocomposites suggested that the photothermal effect of MWCNTs initiated by near-infrared irradiation could modulate the drug release behavior. Overall, this study has developed a facile approach to fabricate bijels-templated bicontinuous porous structures incorporated with functional nanoparticles (or nanofibers) and opened an avenue for making MWCNT-containing porous nanocomposites for controlled drug release applications.

Bicontinuous oxide heteroepitaxy with enhanced photoconductivity

Self-assembled systems have recently attracted extensive attention because they can display a wide range of phase morphologies in nanocomposites, providing a new arena to explore novel phenomena. Among these morphologies, a bicontinuous structure is highly desirable based on its high interface-to-volume ratio and 3D interconnectivity. A bicontinuous nickel oxide (NiO) and tin dioxide (SnO2) heteroepitaxial nanocomposite is revealed here. By controlling their concentration, we fabricated tuneable self-assembled nanostructures from pillars to bicontinuous structures, as evidenced by TEM-energy-dispersive X-ray spectroscopy with a tortuous compositional distribution. The experimentally observed growth modes are consistent with predictions by first-principles calculations. Phase-field simulations are performed to understand 3D microstructure formation and extract key thermodynamic parameters for predicting microstructure morphologies in SnO2:NiO nanocomposites of other concentrations. Furthermore, we demonstrate significantly enhanced photovoltaic properties in a bicontinuous SnO2:NiO nanocomposite macroscopically and microscopically. This research shows a pathway to developing innovative solar cell and photodetector devices based on self-assembled oxides.

Potentiostatic dealloying of PdIn in molten LiCl–KCl eutectic

The high-temperature electrochemical dealloying of the PdIn intermetallic in the LiCl–KCl eutectic at the temperature of 450 °C in potentiostatic mode was carried out. The resulting formation of bi-continuous nano-porous structures with different residual indium content was analyzed at time intervals of 40, 120 and 300 min from the start of the dealloying process. Our results demonstrate that specific bi-continuous structures with a pore size of the order of 100 nm are formed while the temperature of electrolysis is maintained close to the temperature of palladium recrystallization. If the dealloying process is continued for 5 h it is possible to obtain a pure intermetallic Pd2In compound in nanoporous state.

Where Does an Enzyme Reside in a Bicontinuous Structure?

Using enzymes as catalysts in biochemical processes requires to bring them into close contact with the substrates to be processed. For oil-soluble substrates and water soluble enzymes this might be achieved by bringing the water and oil phase in a bicontinuous microemulsion into close contact. In this contribution we review two possible scenarios of how the enzyme and the interface influence each other. Small angle neutron scattering (SANS) and neutron spin echo spectroscopy (NSE) act as a microscope to look into the details of the interfacial region of microemulsions.