Amorphous Polymers Research Articles

Shape‐Memorable, Self‐Healable, Recyclable, and Full‐Color Emissive Ultralong Organic Phosphorescence Vitrimers with Exchangeable Covalent Bonds

AbstractPolymeric materials displaying ultralong organic phosphorescence (UOP) have drawn much attention in the fields of optoelectronics, bioimaging, and information encryption. However, it is challenging to realize polymeric UOP materials with variable mechanical strength, self‐healing, and superior processability. This work presents a low‐cost strategy to achieve polymeric UOP with full‐color‐emission (doping vitrimers with different phosphorescent emitters) by introducing exchangeable covalent cross‐linked bonds. These amorphous polymers show ultralong lifetimes up to 1.75 s under ambient conditions. Impressively, bright afterglow can be observed after soaking the different color films in water for 4 weeks. Furthermore, the polymeric UOP with exchangeable links exhibits self‐healable, recyclable, and shape memory features due to the dynamic covalent networks. These results outline a fundamental strategy to construct multifunctional polymers and pave a way to expanding polymeric phosphorescence materials and their applications.

A Self‐Standing Flexible Gel Polymer Electrolyte for Dendrite‐Free Lithium‐Metal Batteries

AbstractWe discuss here a self‐standing and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium‐metal batteries. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside in situ synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGMEMA. The glyme‐based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer. The LiGPE exhibits high room temperature ionic conductivity (2.3 mS cm−1), high lithium‐transference number of approximately 0.6, good thermal stability (155 °C) and excellent electrochemical properties. At varying current densities, it facilitates a dendrite free plating and de‐plating of lithium across its interface for long periods of time. The high oxidative stability against lithium (Li) up to 5.3 V strongly suggests that it will provide a safer operating Li‐metal battery compared to conventional liquid electrolytes. The LiGPE, when assembled in Li‐metal cell comprising of Li‐metal anode and Li‐ion insertion cathode material (LiFePO4, LFP), demonstrated excellent stability and delivered 90 % of theoretical capacity when cycled over 100 cycles. We discuss here a self‐standing and flexible homogeneous amorphous gel polymer electrolyte (abbreviated as LiGPE) as an alternative electrolyte for lithium‐metal batteries. The gel shows superior interfacial properties with lithium (Li) metal, supressing dendritic growth and enhancing Li‐ion transference number (0.64). The high oxidative stability against Li up to 5.3 V strongly suggests that it will provide a safer operating Li‐metal battery. The LiGPE, comprises of a large volume of liquid lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte confined inside in‐situ synthesized network of acrylonitrile and acrylate, which is poly(ethylene glycol) methyl ether methacrylate or PEGMEMA. The glyme‐based liquid electrolyte in the LiGPE discussed here, which is completely devoid of ionic liquids, essentially plays the role of a plasticizer, enhancing the ionic conductivity (2.3 mS cm−1) without compromising with the mechanical stability or thermal stability (155 °C) of GPE.

Electron spin resonance study on free radicals in cyclic olefin copolymers irradiated by gamma rays at cryogenic and room temperatures

Cyclic olefin copolymers (COCs) are amorphous thermoplastic polymers that require radiation sterilizations when used in prefilled syringes and drug packaging. In the radiation sterilization process, COCs are ionized, and thus, they produce free radicals, which lead to free radical reactions that affect their performance and biosafety. In this study, species of free radicals generated in COCs by γ-ray irradiation and their decay behaviors under different conditions were investigated using electron spin resonance spectroscopy. Results indicated that many alkyl radicals were produced by the irradiation of COCs in liquid nitrogen, which were transformed to peroxy free radicals upon exposure to air. It was confirmed that free radicals centered on secondary and tertiary carbons were predominant after being irradiated at room temperature by an isotropic simulation, and their concentrations depended on the absorbed dose. After 576 h of storage at room temperature, free radicals were nearly annihilated, or almost decayed, near the glass transition temperature. In addition, this study proposes a free radical reaction mechanism for COCs under different post-processing conditions.

Dielectric Properties and Energy Storage of Hybrid/Boron Nitride/Titanium Carbide/Epoxy Nanocomposites

In this study, hybrid boron nitride (BN)/titanium carbide (TiC)/epoxy resin composite nanodielectrics were manufactured and characterized. Their morphological and structural characterization was conducted via scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns, whereas the dielectric behavior was studied by means of broadband dielectric spectroscopy (BDS). Dielectric measurements were carried out from 30 to 160 °C and from 10−1 to 106 Hz, respectively. The dielectric results revealed the existence of three relaxation mechanisms, which from high to low frequencies, at constant temperature, refer to re-arrangement of polar-side groups (β-relaxation) of the macromolecular chains, transition from glassy to rubbery state of the amorphous polymer matrix (α-relaxation) and interfacial polarization (IP) between the polymer matrix and the nanofillers. It was found that, in general, nanodielectrics exhibited enhanced dielectric properties mainly due to the high dielectric permittivity of TiC and the fine dispersion of the fillers, confirmed also by the SEM images. Dynamic analysis conducted for the α-relaxation showed a Vogel–Fulcher–Tammann dependence on temperature. The ability of energy storing of the nanocomposites was examined via their energy density. Optimum performance is exhibited by the 5 phr TiC/1 phr BN/epoxy nanocomposite, reaching an energy storing ability nine times greater than the unfilled matrix.

A thermodynamically-based constitutive theory for amorphous glassy polymers at finite deformations

In this work, a fully thermomechanical coupling constitutive theory is developed for amorphous glassy polymers to explain and predict their complex temperature- and rate-related nonlinear behavior during finite deformations. The foundation for the theory is the original kinematic and thermodynamic framework derived by Bouvard et al. (2013), in which internal state variables with clear physical significance are applied to describe the deformation mechanism of polymers. In contrast to the viewpoint of Bouvard et al. (2013), in the proposed model, we further divide the entanglements into two kinds of molecular microstructures, “permanent entanglements” and “dynamic entanglements”, and describe how their evolution during deformation is regarded as the internal mechanism for the material's macroscopic mechanical properties. Further, a series of new constitutive equations related to “dynamic entanglements” are proposed, which account for the strain softening caused by the dissociation of “dynamic entanglements”, reflect the influence of temperature on the dissociation rate of “dynamic entanglements” and include the effect of rate-dependent glass transition temperature (θg) on the microstructure. The equations related to “permanent entanglements” are also illustrated, which are improved based on the the work of Ames et al. (2009). The predictive capacity of the proposed thermomechanical coupling constitutive theory has been numerically realized by writing a user subroutine for finite element program. Taking polycarbonate (PC) as an example, the simulations are compared with experimental results for compression, shear, tension, and creep at different temperatures and strain rates. It is demonstrated that our proposed constitutive model with a more detailed physical meaning can well reproduce nonlinearity before yield, yield peak, strain softening, hardening and unloading behavior for amorphous glassy polymers under different stress states.

The influence of PEGDA’s molecular weight on its mechanical properties in the context of biomedical applications

Abstract Hydrogels are 3D polymeric networks, which exhibit properties such as softness, viscoelasticity and their ability to absorb large amounts of water. These characteristics make them exceptionally suitable in biomedicine as e.g. tissue scaffolds, drug delivery systems, wound dressings or contact lenses. One of these hydrogels is the biocompatible, hydrophilic and photopolymerizable poly(ethylene glycol) diacrylate (PEGDA). It is used in different biomedical applications due to its tunable mechanical characteristics. In our study, the mechanical properties of different PEGDA hydrogel compositions with variyng molecular masses and contents of water/methanol, were investigated. Different compositions containing 20 m%, 30 m% or 40 m% of PEGDA4K(4,000 g/mol), PEGDA10K(10,000 g/mol) or PEGDA20K(20,000 g/mol) in ultrapure water/methanol (1:2) were produced. Dumbbell-shaped samples were prepared in molds via photopolymerization in a UV chamber. Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) was used as photoinitiator (0.5% w/w). The mechanical testing was performed using a uniaxial testing system. The obtained results showed averagely 78% higher tensile strength (σmax) values for 30 m% and 40 m% samples in comparison with 20 m% samples for all of the tested polymers. PEGDA20K30 m% samples showed the highest σmax among all of the samples with 12.8 MPa. All of the PEGDA20K samples exhibited the highest elongation at break (εB) values (up to 958%), whereas the lowest values were found for PEGDA4K(up to 105%). The obtained stress-strain curves for most of the samples were typical for deformable, amorphous polymers with a deformation upon reaching a critical stress point. The PEGDA materials showed variable mechanical characteristics according to changing molecular mass or polymer concentration. These promising results showed that it should be possible to compose scaffolds with desired mechanical stability according to the needed application.

Sorption–Desorption of Water Vapor by Linear Amorphous Polymers

Sorption–Desorption of Water Vapor by Linear Amorphous Polymers

Study on the Melt Memory Effect and Melt Recrystallization Behavior of Crystallizable Biphenylene Poly(arylene ether sulfone ketone)

Poly(arylene ether sulfone) resins are usually a class of amorphous polymers, which makes them inferior to other semicrystalline aromatic polymers in solvent resistance, chemical stability, and mechanical strength. Herein, a crystallizable poly(arylene ether sulfone ketone) with a high biphenylene content (BD-PESK) was designed and synthesized. BD-PESK showed excellent thermal stability with a Tg of 241 °C and 5% weight loss temperature of 548 °C. Meanwhile, BD-PESK exhibited an obvious melt memory effect at 350–370 °C, but a weak melt memory effect would survive even above its equilibrium melting point due to the high segment rigidity. Under the guidance of this effect, the melt recrystallization of BD-PESK with a maximum crystallinity of 23% can be realized effectively, which made it have excellent solvent resistance similar to the PEEK resin. Semicrystalline BD-PESK showed a high tensile strength up to 86 MPa with a good elongation at break of 23%. Furthermore, due to the combination of high Tg and semicrystallinity, BD-PESK could maintain 71% storage modulus at 240 °C and still 1.4% storage modulus at 300 °C, respectively, showing superior heat resistance to most thermoplastic polymers.

A consistent algorithm for finite-strain visco-hyperelasticity and visco-plasticity of amorphous polymers

Shared rheology elements of soft tissues and additive-manufactured amorphous thermoplastics benefit from a common visco-hyperelastic and visco-plastic constitutive framework. For finite-strain and general visco/elastic/plastic constitutive laws, allowing full anisotropy, we use the Kröner–Lee decomposition of the deformation gradient combined with Mandel stress-based yield function. Relatively weak conditions are necessary for specific laws to be incorporated in this framework. For example, stress-like variables present in visco-elasticity are removed from the list of constitutive unknowns. Constitutive iteration is performed for the elastic Cauchy–Green tensor Ce and the plastic multiplier increment Δλ. The source is here the right Cauchy–Green tensor provided by any discretization. For the integration of the flow law we adopt a scaled/squared series approximation of the matrix exponential. The exact Jacobian of the second Piola–Kirchhoff stress is determined with respect to this source, consistent with the integrator. The resulting system is produced by symbolic source-code generation for each yield function and hyperelastic strain-energy density function with each of the viscous terms added. The constitutive system is solved by a damped Newton–Raphson algorithm with the corresponding stress error being extensively assessed with stress error maps. A cellular beam structure is analyzed and results compared with experiments from our group. Some of the symbolic calculations and closed-form solutions are beyond what is manually achievable and therefore the symbolic sources for this work are made available in a source code repository.

Effects of Polymers on the Drug Solubility and Dissolution Enhancement of Poorly Water-Soluble Rivaroxaban.

The purpose of this study was to investigate the efficacy of hydrophilic polymers in a solid dispersion formulation in improving the solubility and dissolution rate of rivaroxaban (RXB), a poorly soluble drug. The developed solid dispersion consisted of two components, a drug and a polymer, and the drug was dispersed as amorphous particles in a polymer matrix using the spray drying method. Polymeric solid dispersions were evaluated using solubility tests, in vitro dissolution tests, powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and particle size distribution analysis. To maximize physical stability against crystallization and improve the solubility and dissolution of RXB, it is important to select the appropriate polymer type and the optimal ratio of the polymer to the drug. The optimized polyvinyl alcohol (PVA)-based (1/0.5, w/w) and gelatin-based (1/5, w/w) solid dispersion formulations showed 6.3 and 3.6 times higher drug solubilities than pure RXB powder, respectively, and the final dissolution rate was improved by approximately 1.5 times. Scanning electron microscopy and particle size distribution analyses confirmed that the gelatin-based solid dispersion was smaller and more spherical than the PVA-based solid dispersion, suggesting that the gelatin-based solid dispersion had a faster initial dissolution rate. Differential scanning calorimetry and powder X-ray diffraction analyses confirmed that RXB had successfully changed from a crystalline form to an amorphous form, contributing to the improvement in its solubility and dissolution rate. This study provides a strategy for selecting suitable polymers for the development of amorphous polymer solid dispersions that can overcome precipitation during dissolution and stabilization of the amorphous state. In addition, the selected polymer solid dispersion improved the drug solubility and dissolution rate of RXB, a poorly soluble drug, and may be used as a promising drug delivery system.

On the Thermochemical Transition Depression of Cellulose Acetate Composite Membranes.

Gallic acid (GA) and quercetin (QU) are two important bioactive molecules with increased biomedical interest. Cellulose acetate (CA) is a polymer derived from cellulose and is used in various applications. In this work, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study the thermal behavior of electrospun CA membranes loaded with quercetin or gallic acid. It was found that gallic acid and quercetin depress the thermochemical transition (simultaneous softening and decomposition) of CA, in a mechanism similar to that of the glass transition depression of amorphous polymers by plasticizers. The extensive hydrogen bonding, besides the well-known effect of constraining polymer’s softening by keeping macromolecules close to each other, has a secondary effect on the thermochemical transition, i.e., it weakens chemical bonds and, inevitably, facilitates decomposition. This second effect of hydrogen bonding can provide an explanation for an unexpected observation of this study: CA membranes loaded with quercetin or gallic acid soften at lower temperatures; however, at the same time, they decompose to a higher extent than pure CA. Besides optimization of CA processing, the fundamental understanding of the thermochemical transition depression could lead to the design of more sustainable processes for biomass recycling and conversion.

Effect of coagulation treatment on sludge dewatering performance: Application of polysilicate and their mechanism

Coagulation is an extensive and effective pretreatment technology for improving sludge dewatering performance. In this study, polysilicate ferric (PSF), polysilicate aluminum ferric (PSAF), and polysilicate aluminum ferric magnesium (PSAFM) were prepared by copolymerization reaction, and their preparation conditions include pH, temperature (T), and mole ratio were optimized by the single factor and response surface experiments. The optimal preparation conditions of the above coagulants are shown as follows: PSF (pH = 1.0, T = 20 °C, Si/Fe = 1.00), PSAF (pH = 1.0, T = 20 °C, Si/M = 0.40, Fe/Al = 1.562), PSAFM (pH = 1.0, T = 20 °C, Si/M = 1.08, Fe/Al = 2.00, Fe/Mg = 2.00). The characterization of dewatering agents was analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and Fe-Ferron time-by-time complexation colorimetric method. Also, the particle sizes, molecular weights and Zeta potentials were analyzed. The results indicated that Fe3+, Al3+, Mg2+ and polysilicon acid underwent polymerization to form macromolecular amorphous polymers. The performance of polysilicate in sludge dewatering pretreatment were investigated by coagulation experiments, meanwhile, in order to study the influence of polysilicic acid on sludge dewatering performance, commercial polyferric sulfate (PFS) was taken as a comparison. The results showed that polysilicate improved sludge dewatering performance through adsorption bridging effect and charge neutralization. In addition, the content of tightly bound EPS (TB-EPS) and bound water was reduced by polysilicate, which resulted in excellent sludge dewatering performance.

Highly Effective Proton-Conductive Matrix-Mixed Membrane Based on a -SO3H-Functionalized Polyphosphazene.

A polyphosphazene with in-built -SO3H moieties (PP-PhSO3H) was facilely synthesized by the polymeric combination of hexachlorocyclotriphosphazene (HCCP) and sulfonate p-phenylenediamine. Characterization reveals that it is a highly stable amorphous polymer. Proton conductivity investigations showed that the synthesized PP-PhSO3H exhibits a proton conductivity of up to 6.64 × 10-2 S cm-1 at 353 K and 98% relative humidity (RH). This value is almost 2 orders of magnitude higher than the corresponding value for its -SO3H-free analogue, PP-Ph, which is 1.72 × 10-4 S cm-1 when measured under the same condition. Consequently, matrix-mixed membranes (labeled PP-PhSO3H-PAN) were further prepared by mixing PP-PhSO3H with polyacrylonitrile (PAN) in different ratios to test its potential application in the proton-exchange membrane (PEM) fuel cell. The analysis results indicate that when the weight ratio of PP-PhSO3H/PAN is 3:1 [named PP-PhSO3H-PAN (3:1)], its proton conductivity can reach up to 5.05 × 10-2 S cm-1 at 353 K and 98% RH, which is even comparable with those of proton-conductive electrolytes currently used in PEM fuel cells. Furthermore, the continuous test demonstrates that the PP-PhSO3H-PAN (3:1) has long-life reusability. This research reveals that by using phosphazene and sulfonated multiple-amine modules as precursors, organic polymers with excellent proton conductivity for the assembly of matrix-mixed membranes in PEM fuel cells can be easily synthesized by a simple polymeric process.

Ultrasonic evaluation of aging kinetics in amorphous polymer

The physical aging of amorphous polymers induces changes in material properties, which are challenging to detect in situ in industrial settings. Here, we present a nondestructive nonlinear ultrasonic evaluation technique that enables localized measurements of the combined effects of temperature and time in amorphous polymers, without needing to remove materials. The proposed technique is demonstrated using commercial grade poly(vinyl chloride) samples and is supported by analysis of wave–material interactions. The results show that the physical aging of the polymer is described by the Arrhenius equation with an effective activation energy of 103 kJ/mol over the analyzed temperature range.

Temperature Effects in Flexible Adsorption Processes for Amorphous Microporous Polymers.

A collection of atomistic molecular simulations is reported that illustrate the impact of adsorption temperature on species uptake and adsorbate-induced structural rearrangement for amorphous polymers of intrinsic microporosity. Temperature-sensitive structural rearrangement is evaluated by contrasting two methods: standard grand canonical Monte Carlo simulations using a rigid framework approximation and a combined Monte Carlo/molecular dynamics approach that fully incorporates framework flexibility. We report single-component gas phase adsorption isotherms for CH4, C2H4, C2H6, C3H6, C3H8, and CO2 across a temperature range of 250-400 K for models of an archetypal polymer of intrinsic microporosity, PIM-1. A quadratic model is presented that captures two main mechanisms of temperature-dependent adsorption-induced deformation of PIM-1 up to a relative swelling of 1.15: thermal expansion and an increased propensity to swell as a function of species uptake. Two case studies are reported that highlight the critical role of operating temperature in industrial storage and separation applications. The first study focuses on methane storage and delivery applications using a pressure-temperature swing adsorption application (PTSA). We demonstrate that larger working capacities are accompanied by increased volumetric strain between adsorption-desorption steps. The second case study considers PIM-1 as an adsorbent to separate an exemplar ternary syngas mixture at operating temperatures ranging 300-550 K. A temperature threshold of ∼400 K is identified, beyond which adsorption-induced PIM-1 swelling is negligible and the solubility selectivity-loading curve transitions to exhibiting a nearly linear relationship.

Insight in thermomechanical constitutive modeling of shape memory polymers

Shape memory polymers (SMPs) are a new member of the smart materials family. SMPs have found wide applications or potential applications in almost all manmade structures and devices. In order to better design smart structures and devices using SMPs, thermomechanical constitutive modeling is essential. In this insight paper, we will focus on presenting several multi-length-scale and multi-physics modeling frameworks, including the thermodynamics consistent model, elasto-viscoplastic model, statistical mechanics model, and phase evaluation law model. The SMPs modeled will include amorphous one-way shape memory polymers, semicrystalline one-way shape memory polymers, semicrystalline two-way shape memory polymers, and functional and mechanical damage effects on SMPs. Finally, we will give some in-depth perspectives on future development in this area of study.

Atomistic Modeling of Hydrogen and Oxygen Solubility in Semicrystalline PA-6 and HDPE Materials.

Hydrogen is a clean and sustainable energy carrier which plays a major role in the transition of the global energy market to a less fossil fuel dependent future. Polymer-based materials are crucial in the production, storage, transportation, and energy extraction of hydrogen. More insights in the hydrogen-polymers interactions are required to guide material design and product development, especially for hydrogen solubility in polymers, which is crucial in many applications. The current study aims at rationalizing the determining factors of hydrogen solubility in two relevant polymers: polyamide-6 (PA-6) and high density polyethylene (HDPE). Based on atomistic molecular dynamics simulations and experimental data, we have reached several conclusions related to hydrogen and oxygen solubility in these two polymers. The crystal phases of PA-6 and HDPE are impenetrable to hydrogen and oxygen at elevated pressures, despite the small molecular size of hydrogen and oxygen. The practical implication for gas barrier applications is that polymer crystals act as impermeable obstacles and gas migration takes place primarily in the amorphous phase. Experimental hydrogen and oxygen solubilities in PA-6 and HDPE at elevated pressures can be predicted in a semiquantitative manner by molecular simulations. The discrepancies between experimental and predicted values could be attributed to neglect of the effect of crystal regions on the amorphous polymer domains. Although hydrogen is smaller than oxygen, it has been experimentally observed that hydrogen has a lower solubility in PA-6 and HDPE than oxygen. This observation has been confirmed by molecular simulations and attributed to the more favorable energetic interactions of oxygen with PA-6 and PE than of hydrogen. These interactions dominate the solubility behavior over the distribution of the accessible volume in the polymers.

Shear band development under simple shear and the intrinsicality of strain softening of amorphous glassy polymers

The development of shear bands that induced by localized strain inhomogeneity is a characteristic deformation mechanism and determines ductility of amorphous glassy polymers. To investigate the essence of intrinsic strain softening and its influence on shear band evolution under shearing and reverse shearing, a full-network constitutive model based on the micro-mechanism is implemented into the material point method and finite element method respectively. The results show that the shear band nucleates and propagates in forward shearing, and gradually fades until disappears in following reverse shearing when the specimen regains its original geometry. As reverse shearing proceeds or there is a second forward shearing, the homogeneous plastic deformation occurs preferentially in the previously deformed band but it doesn't display any shear band like the initial forward shearing. It means the glassy polymers undergoing plastic deformation cannot be recovered by reverse straining. In further shearing, new shear bands tend to be initiated outside the existing band and then propagates to merge with the previous band. The initiation and propagation of shear band along the shearing direction is caused by the intrinsic strain softening, independent of loading histories and boundary conditions. The widening of shear band is related to the strain hardening. • Origin of intrinsic strain softening lies in the saturation of plastic shear strain. • Amount of intrinsic strain softening keeps fixed. • Glassy polymers undergoing plasticity cannot be recovered by reverse straining. • Full-network model can capture the shear band evolution under reverse shearing.

Fatigue-free artificial ionic skin toughened by self-healable elastic nanomesh

Robust ionic sensing materials that are both fatigue-resistant and self-healable like human skin are essential for soft electronics and robotics with extended service life. However, most existing self-healable artificial ionic skins produced on the basis of network reconfiguration suffer from a low fatigue threshold due to the easy fracture of low-energy amorphous polymer chains with susceptible crack propagation. Here we engineer a fatigue-free yet fully healable hybrid ionic skin toughened by a high-energy, self-healable elastic nanomesh, resembling the repairable nanofibrous interwoven structure of human skin. Such a design affords a superhigh fatigue threshold of 2950 J m−2 while maintaining skin-like compliance, stretchability, and strain-adaptive stiffening response. Moreover, nanofiber tension-induced moisture breathing of ionic matrix leads to a record-high strain-sensing gauge factor of 66.8, far exceeding previous intrinsically stretchable ionic conductors. This concept creates opportunities for designing durable ion-conducting materials that replicate the unparalleled combinatory properties of natural skins more precisely.

Versatile Method of Generating Triboluminescence in Polymer Films Blended with Common Luminophores.

Herein we report a versatile method for the preparation of triboluminescent polymer films by physical blending with common luminophores. This method does not require the presence of a crystalline phase or the use of materials known to be triboluminescent. Emission is generated in response to friction of the polymer surface via triboelectrification, either by rubbing directly or through an inert coating layer, even with low applied stress (<0.1 MPa). Our findings offer a convenient and practical method of preparation of triboluminescent, amorphous polymer films with easily tunable emission properties.