Polymer Network Structure Research Articles

Antimony Nanoparticles Encapsulated in Self-Supported Organic Carbon with a Polymer Network for High-Performance Lithium-Ion Batteries Anode.

Antimony (Sb) demonstrates ascendant reactive activation with lithium ions thanks to its distinctive puckered layer structure. Compared with graphite, Sb can reach a considerable theoretical specific capacity of 660 mAh g−1 by constituting Li3Sb safer reaction potential. Hereupon, with a self-supported organic carbon as a three-dimensional polymer network structure, Sb/carbon (3DPNS-Sb/C) composites were produced through a hydrothermal reaction channel followed by a heat disposal operation. The unique structure shows uniformitarian Sb nanoparticles wrapped in a self-supported organic carbon, alleviating the volume extension of innermost Sb alloying, and conducive to the integrality of the construction. When used as anodes for lithium-ion batteries (LIBs), 3DPNS-Sb/C exhibits a high invertible specific capacity of 511.5 mAh g−1 at a current density of 0.5 A g−1 after 100 cycles and a remarkable rate property of 289.5 mAh g−1 at a current density of 10 A g−1. As anodes, LIBs demonstrate exceptional electrochemical performance.

In-situ preparation of TBIR/CB nanocomposites and its regulation in structure and properties of NR based composites

In order to construct the rubber nanocomposites with desired dual network structures, the trans -1,4-poly (butadiene-co-isoprene) copolymers (TBIR)/carbon black (CB) nanocomposites were prepared by in-situ polymerization in the presence of large amounts of CB using TiCl 4 -type Ziegler-Natta catalysts. It was found that the addition of CB had no obvious negative effects on the catalytic behaviors. Further, the TBIRCB were used to modify NR and the NR/TBIRCB vulcanizates were investigated. Compared with the NR compound, the NR/TBIRCB compounds presented weakened Payne effects and increased bound rubber contents with the increase in CB filling in TBIRCB. Compared with NR and NR/TBIR vulcanizates, the NR/TBIRCB46 vulcanizate with features like excellent filler dispersion and high CB in-situ filling, enhanced interaction between CB and rubber matrix and special polymer network structure constructed from NR/TBIR matrix, showed outstanding comprehensive properties, including greatly reduced rolling resistance, much lower heat built-up and increased abrasion resistance. • Synthesis of new synthetic rubber composites by in-situ polymerization. • NR/TBIRCB46 vulcanizate improve the dispersion of filler in natural rubber. • The rolling resistance, heat build-up and wear of NR/TBIRCB composites are significantly reduced.

Impact of Chain Conformation on Structural Heterogeneity in Polymer Network.

Polymer networks generally consist of an ensemble of single chains. However, understanding how chain conformation affects the structure and properties of polymer networks remains a challenge for optimizing their functionality. Here, we present the fabrication and comparative study of a polymer network composed of collapsed self-entangled chains (intrachain entangled network) and a standard polymer network in which random-coil chains are entangled with each other (interchain entangled network). For poly(methyl methacrylate) thin films composed of these networks, we coupled solvent vapor swelling and single-molecule tracking techniques to examine the anomalies in the dynamics of a small-molecular probe included in the system. We demonstrate that when compared to the interchain entangled network the intrachain one exhibits a more substantial structural heterogeneity, particularly under highly crowded conditions. This network also exhibits physical compactness, which keeps the heterogeneous network structure frozen over time and impedes network plasticization through solvent uptake by the film.

Structure and Rheology of Poly(vinylidene difluoride-co-hexafluoropropylene) in an Ionic Liquid: The Solvent Behaves as a Weak Cross-Linker through Ion–Dipole Interaction

Mixtures of poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and ionic liquids (IL) are known to form flexible, self-healing, and ion-conductive materials that are often referred to as polymer–gel electrolytes. The ion–dipole interaction occurs between PVDF-HFP and the cation; that is, the IL acts not only as a solvent but also as a transient cross-linker to form the network structure, and the density of the binding site (C–F dipole) along the polymer chain is quite high. While the practical importance of this type of polymer/IL has become evident, the fundamental solution properties of these types of polymers have not been clearly understood. Here, we studied the structure and viscoelastic properties of the PVDF-HFP/IL system using infrared spectroscopy, wide- and small-angle X-ray scattering (WAXS/SAXS), and steady-state and oscillatory shear rheology. The polymer network structure was found to maintain the geometrically similar figure ξ ∼ ϕ1/3, where ξ and ϕ denote the correlation length (length of the network strand) and volume fraction of the polymer, respectively. In addition, with an increase in ϕ, the larger-scale structure changed from a mass fractal to a surface fractal morphology at the overlap concentration. The dynamics of this polymer network system is presumed to be governed by the relaxation through repeated association–dissociation processes with the cation. The specific viscosity followed ηsp ∼ ϕ8 in the concentrated solution of PVDF-HFP. The viscometry results indicated that the apparent binding energy increased with ϕ; that is, the C–F dipoles were cooperatively bound to each other via the cations.

Global existence of weak solutions to viscoelastic phase separation part: I. Regular case

We prove the existence of weak solutions to a viscoelastic phase separation problem in two space dimensions. The mathematical model consists of a Cahn–Hilliard-type equation for two-phase flows and the Peterlin–Navier–Stokes equations for viscoelastic fluids. We focus on the case of a polynomial-like potential and suitably bounded coefficient functions. Using the Lagrange–Galerkin finite element method complex behavior of solution for spinodal decomposition including transient polymeric network structures is demonstrated.

From dual-aerogels with semi-interpenetrating polymer network structure to hierarchical porous carbons for advanced supercapacitor electrodes

Herein, dual-aerogels of resorcinol-formaldehyde and polyvinyl alcohol (RF/PVA) with semi-interpenetrating polymer network (semi-IPN) structure are prepared and applied as precursors for preparing the hierarchical porous carbons. PVA serves as the critical skeletal template for macropores and supports the three-dimensional architecture, while KOH impels the increment of micropores and the formation of mesopores, both enlarging the specific surface area. More intriguing, the pore structure and surface area can be tailored by controlling the mass ratio of resorcinol to PVA, thus optimizing the electrochemical performance. As-obtained DAGC-1 with a large specific surface area of 2076 m2 g−1 and three-dimensional hierarchical porous structure exhibits a superior specific capacitance of 320 F g−1 at 1 A g−1 in three-electrode system. Meanwhile, DAGC-1 assembled symmetrical supercapacitor delivers an elevated energy output of 59.8 Wh kg−1 at 350 W kg−1 in EMIMBF4 electrolyte with a wide potential range of 3.5 V. Our work provides a novel synthesis approach deriving hierarchical porous carbons from dual-aerogels with semi-IPN structure, serving as a new highlight for efficient energy storage.

Constructions of special network structure in natural rubber composites for improved anti-fatigue resistance

Nature rubber (NR) as the most widely used rubber material with excellent comprehensive properties suffers the poor fatigue resistance, which seriously affects the serving life of NR products. Blending crystalline components with NR could improve the fatigue properties of NR. However, the desired structures constructed by the crystalline component in the NR based composites were not clear. Herein, three crystalline polymers including isotactic polybutene-1 (PB), trans-1,4-polyisoprene (TPI) and trans-1,4-poly(butadiene-co-isoprene) copolymer rubber (TBIR) with varied crystallinity and crosslinking ability were selected to blend with NR for various network structure construction. The influences of unvulcanized PB and crosslinkable TPI and TBIR on the polymer network structures, filler network structures and then properties of the final composites were studied. It was found, although the modulus and hardness of both filled and unfilled NR/PB (90/10) vulcanizate improved, while the dynamic properties like heat built-up and fatigue resistance decreased greatly when compared with that of NR vulcanizate. While, NR/TBIR (90/10) vulcanizate showed the highest fatigue life. The structures of unfilled and filled NR/TBIR vulcanizates were analyzed to acquire the desired structure for satisfied fatigue properties of NR based composites. The more homogeneous rubber matrix enhanced with nano-scale crystalline lamellar structures and having co-vulcanization crosslinking bonds between NR and TBIR contributed to the greatly improved fatigue resistance, as well as satisfied other mechanical properties.

Structure–property relations in semi‐crystalline combinatorial poly(urethane‐isocyanurate)‐type hydrogels

AbstractWithin the fields of regenerative medicine and tissue engineering, the development of tough hydrogel biomaterials is a challenging topic that has received much attention over the past few years. Recently, a method was developed to synthesize tough combinatorial poly(urethane‐isocyanurate) (PUI)‐type hydrogels by the trimerization of mixtures of NCO‐functionalized prepolymers. As this synthesis approach allows a large degree of freedom in terms of polymer network design with a high level of control over the polymer network structure, the resulting systems are ideally suited for studying structure–property relations in tough hydrogel systems. In this work, we aim to systematically investigate the influence of introducing a hydrophobic component into a PUI polymer network on the mechanical properties of the resulting PUI hydrogels. Additionally, the effect of (the degree of) crystallinity of the hydrophobic network component is investigated. For this, two series of combinatorial PUI hydrogels are synthesized, based on a hydrophilic poly(ethylene glycol) prepolymer and increasing amounts of either a crystallizable hydrophobic prepolymer (poly(ε‐caprolactone)) or an amorphous hydrophobic prepolymer (poly(propylene glycol)). It is shown that the toughness of amorphous PUI hydrogels is hardly influenced by the hydrophobic content, whereas the toughness of semi‐crystalline PUI hydrogels strongly increases with increasing hydrophobic content. Also, the toughness of the latter hydrogels increases further with increasing degree of crystallinity of the hydrogel. Finally, it is shown that the semi‐crystalline PUI hydrogels are promising materials for biomedical adhesive and coating applications, as well as for load‐bearing biomedical applications within the fields of tissue engineering and regenerative medicine. © 2022 Covestro Deutschland AG. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Carbon dots crosslinked gel polymer electrolytes for dendrite‐free and long‐cycle lithium metal batteries

AbstractLithium metal batteries (LMBs) with extremely high energy densities have several advantages among energy storage equipment. However, the uncontrolled growth of dendrites and the flammable liquid electrolytes (LEs) often cause safety accidents. All solid‐state batteries seem to be the ultimate choice, but solvent‐free electrolytes usually fail in terms of conductivity at room temperature. Therefore, gel polymer electrolytes (GPEs) with a simple manufacturing process and high ionic conductivity are considered as the most competitive candidates to resolve the present difficulties. Herein, we design a polymeric network structure via esterification and amidation reactions between polyethylene glycol (PEG) and carbon dots (CDs). After incorporation with polyvinylidene fluoride and some LEs, the as‐prepared PEG–CDs composite electrolytes (PCCEs) show a high ionic conductivity of 5.5 mS/cm and an ion transference number of 0.71 at room temperature, as well as good flexibility and thermostability. When the PCCEs are assembled with lithium metal anodes and LiFePO4 or LiCoO2 cathodes, both the cycling stability and the retention rate of these LMBs show excellent performance at room temperature.

Enhanced toughness and degradable ability of polybenzoxazines/polyhexahydrotriazines interpenetrating polymer networks by sequential cure method

Benzoxazine resins are widely used as matrix resins of composites in the aerospace industry. For example, auxiliary power units and center bodies of an aircraft are usually made by polybenzoxazine composites, and these parts should be replaced periodically for aviation safety. So, resins used in this field would better be strong and economically maintainable. However, traditional polybenzoxazines, which are formed by irreversible crosslinked networks, show brittle and undegradable. These two disadvantages may not only cause component malfunction but also huge maintenance costs. Considering these two points above, we developed a new kind of resin by employing an interpenetrating polymer network (IPN) structure into polybenzoxazine. A series of IPNs were prepared using 3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazine-6-carbaldehyde (HB) and poly-(hexahydrotriazine) (PHT), by thermal polymerization. Various proportions of these two monomers were studied and their mechanical, thermal, and degrade properties were characterized. Fourier transform infrared spectrometer (FTIR) proves that intermolecular H-bonds (OH⋯O) exist between PHB and PHT, which facilitate the formation of homogeneous phase in IPNs. Tension test results show that mechanical properties especially the toughness of these IPNs increase sharply. The minimums of tensile strength and breaking elongation we acquired are 94.29 MPa and 5.63%, respectively, which exhibit 180% and 250% higher than those of pure PHT. In addition, we find that when the molar ratio of PHB/PHT is 2.4, tensile strength of the polymer (PHB/PHT-2.4) exhibits a highest value of 122.75 Mpa, and breaking elongation reaches 9.60%. At the same time, it shows the highest glass transition temperature (Tg) of 211 °C by dynamic thermo-mechanical analysis (DMA), compared with PHT and IPNs of the other proportions. Additionally, PHB/PHT IPNs exhibit a good solution degradability, when immersed for 36 h in a mixed solution, which was prepared by hydrochloric acid/tetrahydrofuran (1:4) mixed solvent. IPNs prepared by PHB/PHT could be totally broken in the solution above, except for PHB/PHT-4.8.

Highly stretchable dual‐cure photosensitive resin for digital light processing printing

AbstractThe two‐stage curing approach is one of the promising strategies to achieve the 3D printing of high‐performance elastomers. Herein, a novel resin formulation that is composed of a photocurable acrylic resin and a mixture of thermocurable isocyanate oligomer/diamine is evaluated by digital light processing technology. Such resin possesses a satisfying viscosity for printing, especially at ambient temperature. For first curing stage, that is, photocurable stage, precisely architectural components with the required shape can be fabricated by a free‐radical photopolymerization. Methyl ethyl ketone oxime that serves as a blocking agent, was employed to ensure the stability of isocyanate resin during this stage. Consecutively, a thermally activated deblocking process is carried out and accompanied by isocyanate/diamine copolymerization, which is the second curing stage. An interpenetrating polymer networks structure in designing resin (25 wt% photocurable resin and 75 wt% thermocurable resin) was formed after thermal curing, which is of significance for achieving excellently comprehensive mechanical properties. Contributed by special structures, it is capable of reaching a 4.67 MPa of tensile strength at 100% strain, while yielding favorable tensile strength of 7.51 MPa as well a maximum elongation at break of 745.3%, which is nearly identical to the initial mechanical performances of pure polyurethane elastomer.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Cyclic Compression Testing of Three Elastomer Types-A Thermoplastic Vulcanizate Elastomer, a Liquid Silicone Rubber and Two Ethylene-Propylene-Diene Rubbers.

Thermoplastic elastomer vulcanizate (TPV) and liquid silicone rubber (LSR) are replacement candidates for ethylene-propylene-diene rubbers (EPDM), as they offer the possibility for two-component injection moulding. In this study, these material types were compared side by side in cyclic compression tests. The materials were also characterized to provide details on the formulations. Compared to the rubbers, the TPV had higher compression set (after a given cycle) and hysteresis loss, and a stronger Mullins effect. This is due to the thermoplastic matrix in the TPV. The LSR had lower compression set (after a given cycle) than the EPDM, but stronger Mullins effect and higher relative hysteresis loss. These differences between the LSR and the EPDM are likely due to differences in polymer network structure and type of filler. Methods for quantifying the Mullins effect are proposed, and correlations between a Mullins index and parameters such as compression set are discussed. The EPDMs showed a distinct trend in compression set, relative hysteresis loss and relaxed stress fraction vs. strain amplitude; these entities were almost independent of strain amplitude in the range 15–35%, while they increased in this range for the TPV and the LSR. The difference between the compression set values of the LSR and the EPDM decreased with increasing strain amplitude and increasing strain recovery time.

Super Adhesive MXene‐based Nanocomposite Hydrogel with Self‐Healable and Conductivity Properties via Radiation Synthesis

Functional adhesive hydrogels have attracted tremendous attention due to their versatile potential applications in electronic skins and biomedical engineering. MXenes are emerging 2D materials that promised to be attractive ideal candidates as nanofillers for nanocomposite hydrogels. Herein, a super adhesive MXene‐based nanocomposite hydrogel with self‐healable and conductivity properties is successfully fabricated via a one‐step γ‐radiation polymerization of 2‐(dimethylamino) ethyl methacrylate (DMAEMA) and Ti3C2Tx MXene nanosheets with ultralow contents serve as a crosslinking agent and functional nanofiller simultaneously. It is found that Ti3C2Tx not only plays an important role in the formation of uniform polymer network structure, but also improves the mechanical strength, conductivity, and adhesive properties of composite hydrogels significantly. The Ti3C2Tx/poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) nanocomposite hydrogel exhibits an ionic conductivity of 1.6 mS cm−1, and a super adhesive strength of 5041 kPa to the copper substrate. The resultant hydrogel also exhibits fast automatic self‐healing ability due to the hydrogen bonds between Ti3C2Tx and PDMAEMA chains. This work provides a new method to synthesize the robust MXene‐based environmentally sensitive nanocomposite adhesive hydrogels.

Polymer Stabilization of Uniform Lying Helix Texture in a Bimesogen-Doped Cholesteric Liquid Crystal for Frequency-Modulated Electro-Optic Responses.

A polymer network (PN) can sustain the uniform lying helix (ULH) texture in a binary cholesteric liquid crystal (LC) comprising a calamitic LC and a bimesogenic LC dimer. Upon copolymerization of a bifunctional monomer with a trifunctional monomer at a concentration of 5 wt% to create the desired polymer network structure, the PN-ULH was obtained with high stability and recoverability even when cycles of helical unwinding-to-rewinding processes were induced after the electrical or thermal treatment. Utilizing dielectric spectroscopy, the flexoelectric-polarization-dominated dielectric relaxation in the PN-ULH state was characterized to determine two frequency regions, f < fflexo and f > fdi, with pronounced and suppressed flexoelectric effect, respectively. It is demonstrated that the cell in the PN-ULH state can operate in the light-intensity modulation mode by the flexoelectric and dielectric effects at f < fflexo and phase-shift mode by the dielectric effect at f > fdi. Moreover, varying the voltage frequency from f < fflexo to f > fdi results in a frequency dispersion of transmittance analogous to that of flexoelectric-polarization-dominated dielectric relaxation. The unique combination of the bimesogen-doped cholesteric LC with a stable and recoverable PN-ULH texture is thus promising for developing a frequency-modulated electro-optic device.

The Effects of Using Waste Engine Oil Bottom on Physical, Rheological Properties and Composite Modification Mechanism of SBS-Modified Asphalt

This research explores the effects of using waste engine oil bottom on physical, rheological properties and composite modification mechanism of SBS-modified asphalt. The SBS asphalt binder was modified by WEOB with different concentrations (2, 4, and 6 wt%). The GC-MS and FTIR spectrometry were conducted to evaluate the chemical compositions of WEOB- and WEOB-modified asphalt. RV, DSR, and BBR were tested to evaluate high- and low-temperature pavement performance. Fluorescence microscope (FM) test, bar thin layer chromatograph (BTLC) test, and AFM test were performed to evaluate the micromorphologies and modification mechanism. The test results showed that a new characteristic peak appeared in the infrared spectrum of the WEOB-modified SBS asphalt, indicating a chemical reaction in the modification process. Incorporation of WEOB improves both the high-temperature and low-temperature properties of the SBS asphalt binder. It was confirmed that with the increase of WEOB concentration, the content of colloid gradually increases, which promotes the swelling and compaction of SBS polymer network structure. Furthermore, WEOB promotes the polarity of SBS and forms graft product MAH-g-SBS with asphalt, thus inhibiting the thermal movement of asphalt molecules. On the contrary, light components have a good correlation with the surface roughness of modified asphalt; the results show that the modified asphalt has good rutting resistance.

Synthesis and characterization of arabinoxylan-bis[2-(methacryloyloxy)ethyl] phosphate crosslinked copolymer network by high energy gamma radiation for use in controlled drug delivery applications

Keeping in view the therapeutic important dietary fiber psyllium, herein this research report its potential has been explored for the formation of sterile hydrogel by high energy radiation induced copolymerization of arabinoxylan-poly bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) for use as drug delivery carrier. The polymeric network structure was characterized by 13C NMR, FTIR, TGA/DTG and DSC, XRD and AFM techniques. Release profile of a drug cefuroxime and best fit kinetic model were determined. The blood –polymer interaction, mucosal-polymer adhesion, antioxidant and mechanical properties were also evaluated. The radiation dose influenced the crosslink density and the mesh size of the hydrogel network. Release profile of a drug cefuroxime followed non-Fickian diffusion and best fitted to first order kinetic model. The grafted product was sterile, porous, antioxidant and mucoadhesive in nature and could be explored for controlled and sustained GIT drug delivery applications.

Response to the comment on: “Dissolved oxygen sensing characteristics of plastic optical fiber coated with hydrogel film” – The wider context of fibre optic oxygen sensing

In, F. Formenti (2021) proposed that ruthenium complexes, as an unsafe and toxic material, are not suitable for clinical applications and indicated that platinum porphyrin has been clinically applied to optical fiber oxygen sensors with short response time. This article will answer the questions raised by F. Formenti from the following aspects: 1.The toxicity of ruthenium complexes was overestimated. This article will briefly outline some biomedical applications based on ruthenium. 2. Hydrogels have been used in different biomedicine purpose, the ruthenium indicator in this article [2] will not leak from the polymer network structure hydrogel. 3. The response time in this article [2] is shorter than reported and the sensing system [2] has other excellent properties.

Polyether-based solid electrolytes with a homogeneous polymer network: effect of the salt concentration on the Li-ion coordination structure.

We report a solid polymer electrolyte with an ideal polyether network that was synthesized by using tetra-functional poly(ethylene glycol) (TetraPEG) and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) salt. The solid TetraPEG electrolyte had few network defects (<5%) and exhibited high mechanical toughness by enduring approximately 11-fold elongation at a 1 : 10 ratio of Li salt to O atoms of PEG (Li/OPEG). We found that the mechanical properties strongly depend on the Li/OPEG ratio, which mainly contributes to the density of crosslinking points in the electrolyte. Raman spectroscopy and high-energy X-ray total scattering were used with all-atom molecular dynamics simulations to visualize the structural effects of Li-ion coordination in the TetraPEG network. At lower salt contents (Li/OPEG = 1 : 10), Li ions were found to preferentially coordinate with OPEG atoms rather than the TFSA anions to form crown ether-like Li+-PEG complexes as ion pair-free species. With increasing salt content, the TFSA anions partially coordinated with Li ions through O atoms of TFSA (OTFSA) to afford contact ion pairs surrounded by both OPEG and OTFSA atoms. Finally, the ion pairing enhanced mononuclear ion pairs as well as multinuclear ionic aggregates when more Li salt was added. This structural change in the Li-ion complexes was directly reflected by the ion-conducting properties of the electrolyte. The TetraPEG electrolyte composed of the ion pair-free Li+ species (Li/OPEG = 1 : 10) exhibited higher ionic conductivity, and the conductivity gradually decreased with increasing salt content because of extensive ion pairing for both mononuclear contact ion pairs and multinuclear aggregates. Regarding the electrochemical properties, the optimum electrolyte composition to realize a reversible Li deposition/dissolution reaction for a negative electrode was found to be Li/OPEG = 1 : 4.

A network-based visco-hyperelastic constitutive model for optically clear adhesives

Optically clear adhesives (OCAs) are widely used as bonding materials in display industries. Accurate characterizations on the mechanical behaviors of OCAs are fundamental inputs in bending stress analysis of foldable displays for the optimal design purpose. Yet only a few works have studied the mechanical behaviors of OCAs. No network-based visco-hyperelastic constitutive model has ever been developed or applied to OCAs. In this work, we propose a visco-hyperelastic constitutive model based on the microscopic structure of polymer networks to characterize the mechanical behaviors of OCAs under different loading conditions. The model considers that the OCA consists of crosslinked networks and free chains, both of which are under topological constraints induced by entanglements. The hyperelastic response comes from the crosslinked networks, while the viscoelastic response originates from the free chains. We test the OCAs produced by 3M by loading them to large deformations with different loading rates. Results show that our model can well capture the visco-hyperelastic mechanical behaviors under these conditions. In addition, we program our constitutive model into ABAQUS UMAT and use two case studies to show the application of our model in finite element simulations.