Tricontinuous Structure Research Articles

Linear Strain Sensors via a Spatial Heteromodulus Tricontinuous Structure Design for High-Resolution Recording of Snoring Breath.

Porous conductive elastomer composites are very attractive for designing flexible and air-permeable mechanical sensors for healthcare, while it is challenging to achieve a linear and sensitive electromechanical response over a wide strain range for high-resolution recording of physiological activities and body motions. Here, a scalable strategy is developed to construct porous elastomer composites with a bamboo-shaped heteromodulus microstructure in the pores for the fabrication of linear stretchable strain sensors. Such a spatial heteromodulus microstructure is fabricated via phase separation and selective location of high-modulus phase during melt compounding of elastomers and thermoplastics, together with green etching of the water-soluble plastic in the tricontinuous elastomer composites. The bamboo-shaped heteromodulus microstructure is constructed on the pore struts via the fracture of a high-modulus polymer self-assembled on the pore surface and relaxation recovery of the elastomer matrix after prestretching, which blocks the propagation of cut-through microcracks upon stretching. The composites with super low resistance after in situ growth of silver nanoparticles sustain up to 110% tensile strain with a linear and sensitive electromechanical response, demonstrating potential applications in discriminating respiration status and monitoring snoring breath. This work unveils a new approach to fabricate high-performance air-permeable strain sensors in a simple and scalable way.

Phase Morphology and Conductive Properties of PBT/POE-g-GMA/PP/CNT Nanocomposites with a Tri-Continuous Structure via Thermal Annealing

In order to improve the conductivity of polymer composites and elucidate the relationship between the microstructure and conductivity, a series of PBT/POE-g-GMA/PP/CNT nanocomposites with a tri-continuous structure and low conductive percolation threshold were prepared by melt blending. Compared to PBT/PP/CNT composites, the PBT/POE-g-GMA/PP/CNT nanocomposites show better conductivity owing to the selective distribution of carbon nanotubes (CNTs) in the POE-g-GMA phase with the same CNT content. The increasing content of the CNTs and POE-g-GMA refines phase morphology, thus influencing the CNTs’ conductive path. Composites containing 10 wt % POE-g-GMA display the lowest conductive percolation threshold at 1.0 phr. In addition, the influencing mechanism of thermal annealing on microstructure and conductivity was methodically investigated. Thermal annealing can effectively enhance the rebuilding of CNT conductive networks and continuity of the POE-g-GMA phase on the premise of the original phase structure, decreasing the volume resistivity of nanocomposites. The nanocomposites obtained in this study possess excellent electrical properties alongside the potential to be a candidate material in fields of sensors, electromagnetic interference shielding, and so forth.

Significantly improved high dielectric MWCNTs filled PVDF/PS/HDPE composites via constructing double bi-continuous structure

Multi-layer composites with vastly difference in electrical properties for each layer are a promising candidate to design high dielectric materials, showing a tremendous promise on dielectric applications. But fabrication of these dielectric materials is relatively complicated, and unsuitable for large-scale production. Herein, a novel dielectric poly (vinylidene fluoride)/polystyrene/high density polyethylene (PVDF/PS/HDPE) composite constructed via tri-continuous structure were designed. And via variation PS concentration to control the compatibilizer effect of PS phase, a smaller PS phase size has been obtained and this composite finally exhibits a double bi-continuous morphology structure. For this double bi-continuous PVDF/PS/HDPE composite, a better dispersion of MWCNT particles increases the density of interfacial charge enrichment, and the increase of the specific surface area of the interfacial layer increases the number of enriched charges, which make the interfacial polarization increase most significantly compared with the other composites. Thus, a high-performance dielectric PVDF/PS/HDPE composite with high ε′ and low tan δ have been realized.

Superstretchable, thermostable and ultrahigh-loading lithium–sulfur batteries based on nanostructural gel cathodes and gel electrolytes

Abstract Lithium–sulfur batteries are desirable for portable and wearable electronic devices because of their high energy density, low cost and environmental friendliness. Herein, the fabrication of superstretchable Li−S batteries based on highly elastic gel cathodes (fracture strain: 1671%), gel electrolytes (fracture strain: 1223%), zigzag Cu wire-interconnected Li anode pieces and soft packages, is demonstrated. A phase inversion approach is developed to prepare gel cathodes composed of a homogeneously distributed 3D porous fluorinated copolymer skeleton, interlaced electron-conductive networks and sulfur-encapsulated hierarchical polar nanocomposites. The highly elastic gel cathodes possess tri-continuous structures with interpenetrated macropores favourable for high sulfur loading, electrolyte permeation and ion transport. The gel electrolytes with an amorphous phase copolymer matrix and tethered anions exhibit high ionic conductivity, thermal stability, flexibility and effective suppression of Li dendrite growth. The soft-packed Li‒S batteries can be stretched up to 420% of their original length, function normally at 80 °C and deliver an ultrahigh areal capacity of 11.0 mAh cm−2 at a sulfur loading of 14 mg cm−2.

Multiscale Tuning of Bi- and Tri-Continuous Structures for Energy Applications

We create bi- and tri-continuous structures by a variety of methods, including liquid-liquid phase separation and growing colloidal crystals. Liquid-liquid phase separation can be arrested using colloidal particles, which jam at the liquid-liquid interface. This creates a structure, called a bijel, where the two liquid phases and the particle layer are all continuous and interpenetrating. Bijels allow for an enormous surface area to volume ratio between the two liquids and have highly tunable mechanical properties. As they can also be post-processed, for example by replacing one of the liquids with a polymer, they are ideal templates for novel energy materials.The bi- and tri-continuous structures we create are well-suited to applications such as electrodes in Li-air batteries, where the oxygen, electrons and electrolyte all require their own pathways.

Insight into the formation of a continuous sheath structure for the PS phase in tri-continuous PVDF/PS/HDPE blends

A hierarchical tri-continuous structure is formed and controlled in PVDF/PS/HDPE ternary blends. A very high level of PS continuity, about 80%, is achieved only with a PS volume composition as low as 11 vol%.

Morphology evolution and the tri-continuous morphology formation of a PVDF/PS/HDPE ternary blend in melt mixing

Manipulate the perfect tri-continuous structure of the PVDF/PS/HDPE system successfully and it can allow preparation for the functionalization of tri-continuous morphology!

Structuring tri-continuous structure multiphase composites with ultralow conductive percolation threshold and excellent electromagnetic shielding effectiveness using simple melt mixing

Tri-continuous structure poly(vinylidene fluoride)/polystyrene/high density polyethylene (PVDF/PS/HDPE) ternary blends was fabricated as a candidate for structuring high electrical performance composites. By adding MWCNTs and tuning the thermodynamic and kinetics conditions, the selective distribution of MWCNTs in interfacial PS phase were formed after melt mixing. These composites displayed ultralow conductive percolation threshold and excellent electromagnetic shielding effectiveness by this structuring process.

The Tricontinuous 3ths(5) Phase: A New Morphology in Copolymer Melts

Self-assembly remains the most efficient route to the formation of ordered nanostructures, including the double gyroid network phase in diblock copolymers based on two intergrown network domains. Here we use self-consistent field theory to show that a tricontinuous structure with monoclinic symmetry, called 3ths(5), based on the intergrowth of three distorted ths nets, is an equilibrium phase of triblock star-copolymer melts when an extended molecular core is introduced. The introduction of the core enhances the role of chain stretching by enforcing larger structural length scales, thus destabilizing the hexagonal columnar phase in favor of morphologies with less packing frustration. This study further demonstrates that the introduction of molecular cores is a general concept for tuning the relative importance of entropic and enthalpic free energy contributions, hence providing a tool to stabilize an extended repertoire of self-assembled nanostructured materials.

Tricontinuous Morphology of Ternary Polymer Blends Driven by Photopolymerization: Reaction and Phase Separation Kinetics

Phase separation of a ternary mixture composed of poly(ethyl acrylate) and poly(ethyl methacrylate) derivatives dissolved in methyl methacrylate monomer was induced and driven by photopolymerization. Upon varying the initial composition of the mixture and the molecular weight of the resulting poly(methyl methacrylate) via changing the light intensity, a wide variety of morphologies ranging from separated double droplets, Janus-like droplets, core–shell, salami, bicontinuous to tricontinuous structures emerged due to the competition between phase separation and polymerization. Among the emerging morphologies, the tricontinuous structures were significant, and the details of the formation process were particularly investigated by using laser-scanning confocal microscopy (LSCM). Time-resolved experiments reveal that these tricontinuous structures were generated via two steps of the consecutive phase separation process. The formation of these tricontinuous structures is discussed with respect to the polymeriz...

High performance materials based on a self‐assembled multiple‐percolated ternary blend

In this study, it will be shown that morphologically tailored tricontinuous ternary blends, comprising polybutylene succinate (PBS), polylactic acid (PLA), and poly (butylene adipate‐co‐terephthalate)(PBAT), can generate new materials with excellent properties. Detailed morphological analysis is used to establish that all three phases in the ternary 33%PBS/33%PLA/33%PBAT blend morphology are highly continuous with a phase structure dominated by complete wetting dynamics. PBS is shown to situate itself between PLA and PBAT. This melt processed, self‐assembled, multiple percolated, blend possesses a high elongation at break (567%), high Young's modulus (1130 MPa), high impact strength (271 J/m), and a storage modulus about 50% higher than pure PBS at room temperature. None of the neat materials demonstrate this combination of high properties and the synergy derives from the tricontinuous structure of the system. The ternary nature of the blend allows for a modulation of the crystallinity behavior as examined by differential scanning calorimeter and X‐ray Diffraction. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3005–3012, 2014

A molecular dynamics simulation on the self-assembly of ABC triblock copolymers. 2. Effects of block sequence

The effect of block sequence on the self-assembly of ABC-type triblock copolymers in the ordered state is investigated using an isothermal-isobaric molecular dynamics simulation. The block sequence has an important effect on the morphology of ABC triblock copolymers. Different morphologies are observed depending on the block sequence as well as the block composition. The triblock copolymers with the volume fraction of 1:1:1 (f A=f B=f C=0.33) show the three phase and four layered lamellar structures irrespective of the block sequence. The A32B16C32 triblock copolymer withf B=0.2 shows a morphology in which cylinders of midblock B are formed at the interface between A and C lamellae, whereas the morphology of triblock copolymer B16C32A32 and C32A32B16 show a cylindrical core-shell structure and a lamellar type morphology, respectively. The A20B40C20 triblock copolymer with the block B as a major component shows a tricontinuous structure, whereas both B40C20A20 and C20A20B40 triblock copolymers exhibit the lamellar structures. When the block B has larger volume fraction withf B=0.75, the matrix is composed of block B, and other two blocks A and C form spherical domains.

Studies on equilibrium structures of complex polymers in condensed systems

The thermodynamic-equilibrium structures of four copolymers with different chain architectures are compared. They are AB diblock, BAB triblock, and ABC triblock copolymers and AB2 star-branched graft copolymers. Their morphological transitions meaningfully differ from one another, reflecting the difference in chain architecture. Two-component polymers barely form bicontinuous structures; however, symmetric ABC triblock copolymers easily form tricontinuous structures composed of two surfaces parallel to a Gyroid minimal surface. All four ABC equilibrium structures have a superlattice structure. Block polymer chains in microphase-separated bulk are elongated in the longitudinal direction in lamellar microphases. Although the deformation manner of the chains restricted in microphases depends on the chain architectures, the volumes of the deformed coils are always the same as those of the unperturbed chains regardless of their architectures. The measured polystyrene/poly(2-vinylpyridine) interfacial thickness is fairly thin, but the observed value is much thicker than the theoretically predicted one. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1645–1655, 2000

The tricontinuous double-gyroid structure from a three-component polymer system

The tricontinuous structure of ABC-type triblock copolymer in bulk at equilibrium was studied by both transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS). Sample is an anionically polymerized isoprene-styrene-2-vinylpyridine triblock copolymer whose volume fraction is 0.22–0.59–0.19 and total molecular weight is 64 000. It was found that computer-simulated images based on tricontinuous structure with two parallel surfaces to the gyroid surface, which is one of the three-dimensionally infinite minimal surfaces agree well with the observed TEM images. Further, calculated diffraction patterns for the same tricontinuous structure well represent the observed SAXS intensity maps on imaging plates. These facts imply that the structure of the present triblock copolymer is the tricontinuous double gyroid structure, whose space group is I4132.

Interfacial structures of triblock copolymers and their chain conformations in bulk

Surface characteristics of a 2-vinylpyridine–styrene–2-vinylpyridine (PSP) two-component triblock copolymer and an isoprene–styrene–2-vinylpyridine (ISP) three-component triblock copolymer, whose volume fractions of their center block polystyrene, φ s, were both 0.5, were compared in connection with their chain conformations. The former exhibited alternating lamellar structure, while the latter revealed periodic tricontinuous structure. Chain dimension of S block of PSP was measured by small angle neutron scattering (SANS) and it has been found that polystyrene chain is elongated toward the direction normal to lamellar interface but the degree of deformation is less than that of SP diblock copolymer. Interfacial thickness of PSP, actually 2-vinylpyridine–styrene-d 8–2-vinylpyridine) (PDP) triblock copolymer was measured by neutron reflectivity and estimated to be 4.5 nm, which is essentially the same as that for SP diblock copolymer interface. Alternatively, the features of tricontinuous structure of ISP were determined to have characteristics of parallel surfaces to G-surface, which is one of the infinite minimal surfaces, by transmission electron microscopy and small angle X-ray scattering.

WC-Co-Diamond nano-composites

Solid state sintering of WC-Co powder compacts at temperatures of 1000–1200 °C gives a partially sintered material, in which the degree of densification increases with temperature. An important characteristic of these partially sintered materials is that the pores are interconnected in three dimensions. Furthermore, by varying the hold times at the lowest sintering temperature, where solid state diffusion predominates, the pore structure can be coarsened without significant reduction in compact dimensions. Thus materials with precisely controlled pore connectivity and scale can easily be produced. Using a gas phase infiltration technique, we have infiltrated such nanoporous structures with graphitic carbon. After infiltration, the graphite-infiltrated WC-Co preform is transformed to WC-Co-Diamond by a high pressure/high temperature treatment. The resulting superhard material has a characteristic tricontinuous structure, which may or may not be functionally graded, depending on the infiltration technique used. Preliminary results on structural characterization and wear testing of these novel triphasic superhard materials are briefly discussed.

Surfaces of tricontinuous structure formed by an ABC triblock copolymer in bulk

Surface characteristics of the tricontinuous structure of a triblock copolymer of the ABC type in bulk has been studied. An isoprene-b-styrene-b-2-vinylpyridine (ISP) triblock copolymer, whose total molecular weight is 100 K and the volume fractions of the three components are 0.26, 0.48 and 0.26, respectively, was used as a sample in this study. It turned out clear by comparison of transmission electron microscopy (TEM) and computer simulation (CS) studies and also by small angle X-ray scattering (SAXS) that the A/B and B/C interfaces of ABC copolymers have the characteristics of the parallel surfaces with constant-mean-curvatures, which are derived from the Schoen’s G-surface, which is one of the minimal surfaces.

Tricontinuous structure in a homopolymer-homopolymer-random-copolymer ternary mixture quenched under the tricritical point.

Tricontinuous structure in a homopolymer-homopolymer-random-copolymer ternary mixture quenched under the tricritical point.

Polymer Engineering and Technology

Abstract Several topics have been selected from among the presentations at the sessions on Processing in Polymer Alloys, High-Performance Polymers and Polymer Engineering and Technology. These are: mesh-like structure in block copolymer/homopolymer mixtures, ordered tricontinuous double-diamond structure of triblock copolymers, size of dispersed phases in polymer blends and in reactive processing, and polymer ionics in block-graft copolymers having poly(ethylene oxide) as graft chains.