Chain Slippage Research Articles

Soybean protein “mechanically interlocked” bonding of polysaccharide and MXene to improve the strength and toughness of biomass adhesive

Simultaneously improving the strength and toughness of soybean protein adhesives is a huge challenge. The multi-scale enhancement strategy proposed in this study introduced MXene nanosheets and oxidized sodium alginate (OSA) to improve mechanical properties. The polymer network framework with high crosslink density dissipates energy by restricting the slip of the SPI molecular chains, and MXene act as stress dispersers in the polymer network in order to solve the challenge of the strength-toughness balance. The prepared biomass-based adhesives with high adhesion (dry/wet shear strength 1.93 MPa/1.33 MPa), high toughness (adhesion work 810.9 mJ), high thermal stability, high residual rate (92.53 %), low moisture absorption rate (11.18 %), and long storage time (12 d). Additionally, the application of SOM-5 adhesive reduces the burden of petrochemical resource extraction for adhesive production and contributes to the sustainable development of the wood industry. Most importantly, it presents an adoptable strategy for resolving the tension between strength and toughness of composite materials.

Humidity‐adaptive, mechanically robust, and recyclable bioplastic films amplified by nanoconfined assembly

AbstractPoly(vinyl alcohol) (PVA) is biodegradable, recyclable, and has high tensile strength. Therefore, it is ideal for the development of environment‐friendly sustainable bioplastics. However, at elevated humidity, the mechanical properties of PVA bioplastic films undergo degradation owing to their intrinsic hydrophilic and hygroscopic nature, hindering their applications. This study proposes a nanoconfined assembly strategy to produce humidity‐adaptive, mechanically robust, and recyclable bioplastic film. The strong hydrogen bonds between PVA and cellulose nanofibrils inhibit the penetration of water molecules into the film to promote humidity resistance. Further, the robust coordination interactions between bentonite nanoplates, PVA, and cellulose nanofibrils restrict the slip of polymer chains during deformation, leading to enhanced mechanical properties. Benefiting from the nanoconfined assembly architecture in aggregated composites, the resulting reinforced PVA film simultaneously exhibits strength, stiffness, toughness, fracture energy, and tearing energy of 55.9 MPa, 1,275.6 MPa, 162.9 MJ m−3, 630.9 kJ m−2, and 465.0 kJ m−2, respectively. Moreover, the film maintains a strength of approximately 48.7 MPa even at 80% relative humidity for 180 days. This efficient design strategy applies to diverse scales and structured cellulose biomacromolecules. Moreover, it facilitates the application of recyclable high‐performance bioplastic films to settings that require high humidity tolerance.

Investigation of Dual Network Construction for Toughening in Bio-Based Polyamide Composites.

This study investigated the role of constructing a dual network in toughening bio-based long-chain polyamide 610 (PA610) composites. Rheological studies were conducted to reveal the effects of toughening agent type and content on the material properties. According to the variation trend of mechanical properties and the appearance of a rheological low-frequency plateau of the materials, the percolation network concentration ϕc of the toughening agent in the PA610 matrix was determined to be 13.5 vol.%. The interfacial interaction of the composite was evaluated through the percolation theory, and the scaling value v = 1.36 for both indicated the good affinity between PA610 and the toughening agent. Rheology results found that the combination of ethylene terpolymer (PTW) and maleic anhydride-g-styrene-b-(ethylene-butylene)-b-styrene (MAH-SEBS) could achieve an optimal balance between the mechanical properties and fluidity of the composites. Furthermore, the addition of ultra-high-molecular-weight polytetrafluoroethylene (PTFE), in conjunction with the toughening agent, facilitated the construction of a dual semi-interpenetrating network. The strengthened intermolecular interactions restricted the relative slippage and mobility of the polymer chains and therefore enhanced the strength and toughness of the material. This study provides new possibilities and approaches for optimizing the comprehensive properties of bio-based polyamide materials.

Evolution of elliptical SAXS patterns in aligned systems.

Small-angle X-ray and neutron scattering (SAXS and SANS) patterns from certain semicrystalline polymers and liquid crystals contain discrete reflections from ordered assemblies and central diffuse scattering (CDS) from uncorrelated structures. Systems with imperfectly ordered lamellar structures aligned by stretching or by a magnetic field produce four distinct SAXS patterns: two-point 'banana', four-point pattern, four-point 'eyebrow' and four-point 'butterfly'. The peak intensities of the reflections lie not on a layer line, or the arc of a circle, but on an elliptical trajectory. Modeling shows that randomly placed lamellar stacks modified by chain slip and stack rotation or interlamellar shear can create these forms. On deformation, the isotropic CDS becomes an equatorial streak with an oval, diamond or two-bladed propeller shape, which can be analyzed by separation into isotropic and oriented components. The streak has elliptical intensity contours, a natural consequence of the imperfect alignment of the elongated scattering objects. Both equatorial streaks and two- and four-point reflections can be fitted in elliptical coordinates with relatively few parameters. Equatorial streaks can be analyzed to obtain the size and orientation of voids, fibrils or surfaces. Analyses of the lamellar reflection yield lamellar spacing, stack orientation (interlamellar shear) angle α and chain slip angle ϕ, as well as the size distribution of the lamellar stacks. Currently available computational tools allow these microstructural parameters to be rapidly refined.

Aramid Honeycomb Cores under Constant Pressure: Unveiling the Out-of-Plane Compression Deformation.

The primary challenge during the secondary bonding process of full-height honeycomb sandwich structures is the aramid honeycomb core's height shrinkage. This paper systematically investigated the height evolution behavior of the honeycomb core by using a creep testing machine. The results showed that the out-of-plane compression deformation curve of aramid honeycomb cores is mainly divided into three stages: the dehumidification stage, the pressurization stage and the creep stage. Under conditions of high temperature and pressure, height shrinkage was attributed to the dehydration caused by moisture infiltration, and the compression creep resulted from the slippage of polymer molecular chains. Dehydration shrinkage is stable, whereas compression creep reflects typical viscoelastic polymer characteristics. By employing the viscoelastic Burgers mechanical model and applying the nonlinear surface fitting method, the total height shrinkage deformation behavior of the aramid honeycomb core during the curing process can be accurately predicted by summing the above three stages. This research contributes valuable insights for the manufacturing process of honeycomb sandwich structures.

Effects of network structure on the viscoelastic creep and delayed fracture of polyelectrolyte elastomers

The past decade has witnessed a significant surge in the field of stretchable ionotronics, wherein stretchable ionic conductors play an essential role. Polyelectrolyte elastomers have been featured as the most promising stretchable ionic conductors for engineering practice owing to their leakage-free nature. However, the inherent viscosity of the ionized polymer networks confounds the responses of the materials thus hampering the applicability of the devices. Therefore, it is of significant importance to study the viscoelastic behaviors and understand the overlayed molecular mechanism. In this work, we study the effects of network structure on the viscoelastic creep and delayed fracture of polyelectrolyte elastomers. We design and synthesize poly(1-[2acryloyloxyethyl]-3-butylimidazolium bis(trifluoromethane) sulfonimide-co-methyl acrylate) elastomer and tune the network structure by changing the covalent crosslink density and the molar ratio between the ionic segment and the neutral segment, which are the two most crucial structural parameters. We perform tensile and creep tests for polyelectrolyte elastomers of different compositions and interpret the creep results, with emphasis placed on the effects of applied stress and strain hardening. In general, the creep deformation is mitigated with increasing covalent crosslink density and the molar ratio between the ionic segment and the neutral segment, suggesting that creep is mainly due to the breakage of ionic bonds and the slippage and movement of polymer chains. This work promotes the understanding of the viscoelastic behaviors of polyelectrolyte elastomers and provides insights for tailoring the mechanical properties through the rational design of polymer networks, which is expected to facilitate the development of next-generation stretchable ionotronic devices.

Self‐healing waterborne polyurethane elastomers based on synergistic hydrogen, disulfide and borate bonding for composite conductors

AbstractAs a functional material, polyurethane elastomers have found different applications in a variety of fields such as flexible electronics and smart coatings, but due to the damage during use, they are often endowed with self‐healing properties. However, conventional intrinsically self‐healing polyurethanes often don't balance excellent mechanical and self‐healing properties, so it has become crucial to prepare polyurethane elastomers with excellent self‐healing properties and high mechanical properties. In this study, a self‐healing waterborne polyurethane elastomers (IP‐DTDAx‐BAy‐WPU‐n) was synthesized based on 4, 4‐diaminodiphenyl sulfide (DTDA) boronic acid (BA). The disulfide bond has high motility at low temperatures and induces molecular‐level healing at the damaged interface, contributing to good repair under mild conditions. The borate ester bond limits intermolecular chain slippage and improves the mechanical properties as a dynamic cross‐linking point, while its dynamic reversible effect can synergistically improve the self‐healing ability. The results show that the synthesized elastomer films have good mechanical properties (strength 23.21 MPa, elongation at break 1259.08%, toughness 83.28 MJ m−3), good elastic recovery and self‐healing properties (93%). Furthermore, a composite conductors (IP‐DTDAx‐BAy‐WPU/AgNWs) with self‐healing properties was prepared by compositing AgNWs nanowires with polyurethane elastomers, which laid the foundation for its application in flexible electronic devices and wearable sensing devices.

Simultaneously achieving excellent heat aging resistance and grip performance in carbon black/glass flake/EPDM rubber composite for overhead line spacers

The preparation of wire clamp rubber with semiconductivity, low compression set (C-Set), high mechanical strength, heat aging resistance, and high grip strength is vital for overhead line spacers. This study delves into the formulation design of high-performance ethylene-propylene-diene monomer (EPDM) composite materials for wire clamp rubber. The effects of the vulcanization system, carbon black type, and loading on the essential material properties of EPDM rubber were investigated. The results showed that a hybrid vulcanization system containing peroxide and sulfur simultaneously endowed EPDM rubber with high elasticity and tear strength. N330 carbon black-filled EPDM rubber had the advantages of semiconductivity and high tensile strength, and N774 carbon black-filled EPDM rubber exhibited low C-Set and high heat aging resistance. When EPDM rubber was reinforced with the mixture of 50 phr N330 and 20 phr N774 carbon black, the rubber synchronously exhibited semiconductivity (2.64×106 Ω·cm), high tensile strength (20.2 MPa), low C-Set (32.5%, 150°C×3d), and high heat aging resistance (maintaining 98% of its initial tensile strength after aging at 150°C for 3d). In addition, introducing a 10-phr glass flake into EPDM wire clamp rubber improved the grip force by 83%. The improvement mechanism may be attributed to the increased compression stress of wire clamp rubber on cable and the restricted slippage of rubber molecular chains.

Effect of grain boundaries, cure, and temperature on the thermomechanical properties of epoxy/graphene composites

AbstractIn this study, molecular dynamics (MD) method was used to systematically investigate the effects of grain boundaries (GBs), degree of cure and temperature on the mechanical properties and thermal stability of epoxy/graphene composites. Uniaxial tensile simulations were performed for pristine graphene and graphene containing GBs reinforced epoxy composites with different degrees of cure. Results show that the yield strength and Young's modulus of epoxy/graphene composites increase with the degree of cure. The behind mechanisms can be attributed to the stronger bonding interaction between epoxy chains. The mechanical properties of epoxy/graphene composites with high degree of cure are more sensitive to GB types. The glass transition temperature (Tg) of pristine graphene and graphene containing GBs reinforced epoxy composites presents an increasing trend with the degree of cure. The introduction of GBs can enhance the Tg of epoxy/graphene composites because of the appropriate wrinkles of GBs in graphene sheets helping to block the slippage of epoxy chains. The MD predicted results of Tg are in good agreement with existing experimental data and the DiBenedetto relationship can be applied using the MD parameters. Both yield strength and Young's modulus of epoxy/graphene composites decrease with temperature, which is mainly due to the weak interface interactions at high temperature and the sufficient energy of atoms at high temperature to overcome the energy barrier. GBs present diverse effects on the yield strength and Young's modulus at different temperatures. This work provides a theoretical basis for the application of epoxy composites reinforced with graphene containing GBs under different conditions.Highlights The thermomechanical properties of epoxy/graphene composites are studied. The coupling effects of GBs, cure degree, and temperature are evidenced. The existence of GBs can improve the Tg of epoxy/graphene composites. MD predicted Tg agrees well with experimental data using the WLF relationship.

Fluorenyl-based polyurethane efficiently improves the flexibility and photovoltaic performance of organic solar cells

Introducing proper insulating polymer in the active layer can improve the photovoltaic and mechanical properties of organic solar cells. Here, we design and synthesize a polyurethane insulating material K-BA20 (or 50) containing PDMS and 2D aryl block 9,9-diphenyl-9H-fluorene (DPF). Isophorone diisocyanate (IPDI) is selected as the connection unit and hydrogen bond is introduced to reduce the chain slippage caused by excessive one-dimensional structure. This strategy can enhance the adhesion between components, which can successfully improve the photovoltaic performance and mechanical properties of the devices. When 5 and 15 wt% K-BA20 was introduced into the PM6:Y6-based system, the short-circuit current density (JSC) of 26.71 and 26.65 mA cm−2, and the power conversion efficiency (PCE) of 16.67% and 16.05% were obtained. More interestingly, the active layer introduced K-BA20 with low DPF ratio has good stretchable properties, while K-BA50 with high DPF ratio has more stable flexibility. The breaking elongation of the blend film with introducing 15 wt% K-BA20 was increased 3.2-fold, from 5.81% to 18.46%, and the PM6:Y6-based flexible devices after doping 5 wt% K-BA50 can still maintain half of the initial efficiency under 600 bending fatigues. Hence, this work shows that introducing K-BA20 (or 50) into PM6:Y6 -based devices can bring out a series of positive feedbacks in terms of charge recombination, crystallinity and molecular interaction. It can be seen that constructing new insulating polyurethane materials with rigid and flexible segments is an effective strategy for development of flexible organic solar cells.

Programming hydrogel adhesion with engineered polymer network topology

Hydrogel adhesion that can be easily modulated in magnitude, space, and time is desirable in many emerging applications ranging from tissue engineering and soft robotics to wearable devices. In synthetic materials, these complex adhesion behaviors are often achieved individually with mechanisms and apparatus that are difficult to integrate. Here, we report a universal strategy to embody multifaceted adhesion programmability in synthetic hydrogels. By designing the surface network topology of a hydrogel, supramolecular linkages that result in contrasting adhesion behaviors are formed on the hydrogel interface. The incorporation of different topological linkages leads to dynamically tunable adhesion with high-resolution spatial programmability without alteration of bulk mechanics and chemistry. Further, the association of linkages enables stable and tunable adhesion kinetics that can be tailored to suit different applications. We rationalize the physics of polymer chain slippage, rupture, and diffusion at play in the emergence of the programmable behaviors. With the understanding, we design and fabricate various soft devices such as smart wound patches, fluidic channels, drug-eluting devices, and reconfigurable soft robotics. Our study presents a simple and robust platform in which adhesion controllability in multiple aspects can be easily integrated into a single design of a hydrogel network.

Comb Polybutadiene with Long Polystyrene Side Chains: A Solution for Tunable Flowability and Enhancing Dielectric Properties in High-Frequency Printed Board Adhesive Films.

Liquid high-vinyl polybutadiene (PB) possessed excellent dielectric properties, rendering them suitable candidates for adhesive films of high-frequency printed boards. However, their inherent low molecular weights resulted in chain slippage and overflow during processing, thereby diminishing the performance of the adhesive films. To address this challenge, we synthesized comb PB with long polystyrene side chains via reversible addition-fragmentation chain transfer (RAFT) polymerization, effectively immobilizing the PB backbone and restricting relative chain slippage. Controlling the length and number of "comb teeth" (styrene side chains) efficiently regulated the flowability of comb PB, achieving distinct flow states. Simultaneously, molecular dynamics simulations revealed that the elongated and inflexible polystyrene side chains of comb PB could create minuscule cavities, which impeded close packing of molecules and led to low dielectric constants (2.39/2.01, 1 MHz/10 GHz) and ultralow dielectric losses (0.0071/0.0016, 1 MHz/10 GHz). Furthermore, a series of printed circuit boards were fabricated using a comb PB adhesive film, and the signal loss was significantly reduced to 48.8% (19 GHz) in comparison with a commercial epoxy adhesive. This study demonstrated the potential of comb PB with polystyrene side chains to achieve desirable flow and dielectric properties by introducing tangles, large volume potential resistance, and microporosity compared with block structures.

Low-Temperature Alignment of Conjugated Polymers by Plasticizer-Aided Physical Rubbing.

Rubbing-induced alignment of conjugated polymers issystematically investigated in terms of intra- and inter-molecular interaction. Various polymer films with a broad range of polymer chain rigidity arerubbed, and the degree of polymer chain alignment isquantitatively characterized. The rubbing technique effectively aligns crystalline domains in conjugated polymer films when the temperature approaches the critical rubbing temperature ( ), at which the rearrangement and the slip of polymer chains are possible. A polymer with significant intra-/inter-molecular interactions exhibits higher , though quantitative analysis reveals an intermediately aligned state at temperature Tr ' lower than . This state originates from polymer chain aggregation in an amorphous domain. The intermediately aligned state can be controlled by plasticizer, which enables low-temperature alignment of high-mobility polymer film by reducing Tr ' to near 100 °C, increases the crystallinity, and improves the alignment effect at this state comparable to that of the completely aligned state obtained at extremely high temperatures.

The micro response mechanisms of foamed polymer rehabilitation material under compression: From a closed cell view

Non-aqueous reactive foamed polyurethanes are widely used in the non-excavation rehabilitation of infrastructures and fundamental engineering. However, the effect of a microscopic cell on the understanding of micro-mechanical properties of a polyurethane is not clearly stated. In this work, a molecular model of a polyurethane closed cell is established corresponding to the field emission scanning electron microscopy results. Molecular dynamics simulations were subsequently employed to investigate the effect of a closed cell on the micro-mechanical response of polyurethane during compression. Based on the layered non-affine displacement and internal structure variables, we find that the existence of cells reduces changes in the polymer chain structure, i.e., the bond stretching, bond angle bending, and dihedral angle rotation. This makes slippage of the polymer chain more violent, and the farther away from the centre of the cell, the greater the level of the polymer chain slippage. In other words, chain slippage plays a key role in reducing the mechanical properties of a polymer. What’ s more, it is found that the number of hydrogen bonds in the cell is significantly less than that in the elastomer, which also could reduce the mechanical properties of foamed polyurethane. This study provides an efficient route for studying the micro-mechanical characterization of foamed polyurethane.

Molecular Dynamics Simulation on Tensile Behavior of Cellulose at Different Strain Rates

At present, most high-performance cellulose matrix composites only use cellulose as reinforcement material, which is an obstacle to maximize the advantages of nanocellulose in structure and properties. The development of new functional nanocomposites with cellulose as the main component can better meet people’s needs for high-performance and degradable composites, which requires a comprehensive and thorough understanding of cellulose. Considering the limitations of physical experiments, we performed molecular dynamics simulation of the uniaxial tensile behavior of the cellulose system at three different strain rates (10−4/ps, 10−5/ps, and 10−6/ps), and the stress-strain responses of cellulose systems at different strain rates are obtained. The effect of the strain rate on the mechanical properties of amorphous cellulose system during the tensile processes is analyzed. The deformation mechanism of cellulose amorphous system during the tensile processes is characterized by the energy changes of the different terms including dihedral angle torsion term, bond tensile term, angle bending term, and nonbond term. Structural evolution of the cellulose crystal system during the tensile processes is used to explain the failure mechanism of cellulose. The kinetic simulation results show that the mechanical properties of the cellulose amorphous system increase with the increase of strain rate. Compared with the strain rate of 10−5/ps, the elastic modulus of the system increases by 6.73 GPa at the strain rate 10−4/ps. During the tensile processes, cellulose amorphous region adapts to the applied load mainly through the stretching of the cellulose macromolecular chains, i.e., the deformation of bond lengths and bond angles, without any breakage of the molecular chains. The main causes of chain lengthening at different strain rates are different. The failure of cellulose is caused by the slip and rearrangement of some molecular chains in the crystal structure.

Mechanoresponsive ionic elastomers with Ultra-Stretchability, high toughness, fatigue resistance, and extreme temperature resistance

In the development of elastic materials, the non-synergy between stretchability and toughness is a challenge. Herein, we propose a rational design of a composite hydrogel by introducing strongly polarized hydrated Li-ion clusters, electron-withdrawing carboxyl groups, and Sn(II) complexation into hydrogen-bonded poly(acrylamide) (PAM) network. Weak interaction between Li-ions and amide groups facilitates the rapid flipping and slipping of the PAM chains during stretching, optimizing the stretchability of the hydrogel. This composite also provides an energy-dispersing mechanism based on strong ionic complexation between Sn(II) and amide groups, which improves its toughness. As-prepared composite hydrogel simultaneously exhibits high stretchability (>7000% elongation), ultra toughness of 580 kPa, excellent fatigue resistance and extreme temperature resistance (elastic at − 60 and 70 °C). Due to its excellent comprehensive performances, the present soft material has broad application prospects in agriculture, medicine, construction, and machinery.

A thermo-viscoelastic constitutive model addressing the cyclic shape memory effect for thermo-induced shape memory polymers

The cyclic shape memory effect of thermo-induced shape memory polymers (TSMPs) is a typical thermo-mechanical process that can be affected by thermo-mechanical loading histories. During the deformation stage of the cyclic shape memory effect, polymer chains exhibit the initial dissociation of sub-entanglements, slipping and orientation with the increase in the deformation. The strain can be recovered with the internal rotation of the dihedral angle due to the enhancing motion of polymer chains during the reheating. Based on the rheological theory, a thermo-viscoelastic model is proposed to capture the cyclic shape memory effect of TSMPs. A temperature-dependent stress threshold value is introduced to reflect the slipping of polymer chains. In order to take into account how orientation affects the cyclic shape memory effect, a relationship between the strain and orientation is constructed and introduced into the evolution equations of elastic modulus, viscosity and irrecoverable strain. By comparing the experimental and simulated results at different loading levels and numbers of cycles, the proposed model is verified. The results show that the proposed model can reasonably predict the cyclic shape memory effect of TSMPs.

Совершенствование конструкции цепных пильных аппаратов

At the present time cutting of trees, delimbing, and crosscutting with gasoline-powered saws and logging machines are carried out in the forestry cutting area operations with the help of chain saws. Therefore, the efficiency of forestry work depends on the reliability and performance of the chain saw machine. The problem of increasing the reliability of sawing machines, increasing their service life becomes particularly relevant due to a sharp decrease in the volume of logging with the use of multi-operator logging machines. In this regard, the wide use of efficient motor tools, improvement of their design, especially the chain saw machine, with regard to reducing the harmful effect on the operator is of great importance. Poor quality and performance of domestic machinery has led to the fact that mainly imported tools are used in Russia, while their price and maintenance costs are constantly increasing and, consequently, the cost of harvested wood increases too. In this regard, it is important to develop and introduce new, more perfect tool designs that are not only as good as the reliability and performance of the imported equipment, but even much better. Taking it into account, we can consider that the issue of chain saw research with regard to the specifics of its design, as well as its science-based improvement will increase the operational performance and reliability of machines, which is important for the logging industry. One of the main causes of saw unit failures is the increased wear of its components accompanied by the improper saw chain tensioning. Currently, the proposed devices for regulating the tension of the saw chain require periodic stopping of the saw, as none of the devices provides its automatic tensioning. Thus, the purpose of the research is to improve the reliability and service life of chain saws of forestry machinery on the basis of improving the design that provides automatic tensioning of the saw chain. The paper describes the design solutions to improve the saw machine, that is the design of the device that provides automatic tensioning of the saw chain when the saw bar is fixed, allowing to increase the reliability and service life of chain saws, to reduce the chain slipping during the work, which will increase the safety of work and reduce the risk of injury to the operator.

An Elastic Cross-Linked Binder for Silicon Anodes in Lithium-Ion Batteries with a High Mass Loading

Due to the urgent demand for lithium-ion batteries (LIBs) with a high energy density, silicon (Si) possessing an ultrahigh capacity has aroused wide attention. However, its practical application is seriously hindered by enormous volume changes of the Si anode during cycling. Developing novel binders suitable for the Si anode has proven to be an effective strategy to improve its electrochemical performance. Herein, we constructed a three-dimensional network binder, in which the polyacrylic acid (PAA) long chains are cross-linked with one kind of amino acid, lysine (Lys). The abundant polar groups in PAA/Lys enable it to tightly adhere to the Si particles via hydrogen bonds, and the cross-linked structure prevents irreversible slipping of the PAA chains upon volume variation of the particles. The Si used was obtained from a sustainable route by recycling photovoltaic waste silicon. With high elasticity and strong adhesion, the PAA/Lys binder can effectively keep the structural integrity of the Si electrode and improve its electrochemical performance. The Si electrode using the PAA/Lys binder exhibits a good cycling stability (1008 mAh g-1 at 2 A g-1 after 250 cycles). Even with a high mass loading of 3.03 mg cm-2, the Si anode can remain stable for 100 cycles at a high fixed areal capacity of 3.03 mAh cm-2. This work gives a practical method to make stable Si electrodes using sustainable Si source and environmentally friendly amino acid-based binders.

Biocompatible shape-memory poly(propylene carbonate)/silk fibroin blend with body temperature responsiveness.

The high value-added medical applications surely represent the leading edge of the shape-memory materials (SMPs) field. Herein, the biomedical SMPs were easily prepared via incorporating silk fibroin (SF) into poly(propylene carbonate) (PPC) through directly melt blending. Based on the intrinsic glass transition of PPC at ∼37 °C, the blends showed a body temperature responsiveness without a complex procedure for adjusting the switching temperature. By varying the SF content, the blend exhibited tunable shape-memory effects (SME), with a first enhancing but then worsening shape recoverability and a stable and excellent shape fixity. And the blend with 3 wt% SF achieved the best SME, enabling an efficient shape reconfiguration under a 37 °C water bath. It was revealed that SF acted as physical cross-links to connect the PPC chains forming a shape-memory network, thus can well retard irreversible the chain slipping of PPC, leading to the improvement of recoverability. Moreover, the results obtained from cell compatibility testing showed the huge application potential of this material in the biomedical field. This work proposed a facile preparation strategy for developing biocompatible body heat actuated shape-memory materials.