Tough Films Research Articles

Bioadhesive First-Aid Patch with Rapid Hemostasis and High Toughness Designed for Sutureless Sealing of Acute Bleeding Wounds.

The global military and civilian sectors express widespread concern over the significant hemorrhage associated with various acute wounds. Such bleedings lead to numerous casualties in military confrontations, traffic accidents, and surgical injuries. Consequently, the rapid control of the bleedings, particularly for extensive and pressurized wounds, is crucial in first-aid situations. In this work, a double-layered bioadhesive patch that combines a superabsorbent adhesive hydrogel with a highly tough antibacterial polyurethane film, which is called as Bio-Patch, is proposed. The Bio-Patch demonstrates superior mechanical strength and forms robust bioadhesion to acute bleeding wounds. Furthermore, the Bio-Patch enables protecting against external Gram-negative and Gram-positive bacteria. Thanks to the double-layered structures having synergistic functions of stable barrier and robust adhesion, the Bio-Patch provides optimal wound sealing (burst strength exceeding 310mmHg) both in vitro and in vivo. It also demonstrates superior hemostatic effects (less than 30 s) in vivo. This offers promising opportunities for rapid control of extensive and pressurized hemorrhage in first-aid clinical scenarios.

The Elevated Temperature Tribological Performance of Tough and Superhard TaMoN-Ag films with Solute and Nanocomposite Structures

Abstract Films have been prepared with not only high hardness to guarantee excellent wear resistance but also high toughness to prevent brittle fracture at low to middle-high temperatures. On the basis of ternary transition metal nitrides with significantly improved hardness and toughness, TaMoN-Ag films with solute and nanocomposite structure were prepared by DC magnetron sputtering technology. Friction wear tests were performed between room temperature (RT) and 700 °C. When doping with trace amounts of Ag atoms (∼1.12 at.%, 4 W), TaMoN-Ag films maintain solid solution structure. TaMoN-Ag films with the Ag target power is 4 W show the highest hardness (H∼62.1 GPa), which is 58% higher than TaMoN film and 44% better than that of TaMoN films. Meanwhile, a lower wear rate (KIC∼5.87×10-7 mm3/N·m) is obtained. The tribological properties of TaMoN-Ag films at room temperatures are related to the H3/E2 and lubricious Ag phase, while the tribological properties at high temperatures are mainly due to the formation of lubricating binary metal oxides (AgxTMyOz (Magnéli phases)). The composite films generally have good resistance to plastic deformation.

Aromatic (co)polycarbonates bearing pendant 2,3-dimethylmaleimido group based upon a new phthalimidine-containing “cardo” bisphenol

A new “cardo” bisphenol viz., 1-(2-(1,1-bis(4-hydroxyphenyl)-3-oxoisoindolin-2-yl)ethyl)-3,4-dimethyl-1H-pyrrole-2,5-dione (PPH-MA) was synthesized in a two-step reaction sequence starting from phenolphthalein. PPH-MA was utilized as a step-growth monomer for the synthesis of a homo- and fourco-polycarbonates bearing pendant 2,3-dimethylmaleimido groups (PC-MAs) via solution polycondensation of PPH-MA or various mol % compositions of PPH-MA and bisphenol-A, respectively, with triphosgene.1H NMR spectroscopy confirmed the chemical structure and composition of PC-MAs. Inherent viscosity and number average molecular weight values of PC-MAs were in the range 0.45–0.64 dL g−1 and 18,300 − 36,200 g mol−1, respectively, indicating the formation of polymers of medium to reasonably high molecular weights. Tough, transparent and flexible films of PC-MAs could be cast from chloroform solution. X-ray diffraction studies indicated the amorphous nature of PC-MAs. The 10% weight loss temperature (T10) values of PC-MAs were in the range 373–443 °C indicating their good thermal stability.

Aromatic (Co)polycarbonates bearing pendant norbornenyl groups: Synthesis, characterization and post-polymerization modification

A homo- and three co-polycarbonates (PC-NBs) bearing pendant norbornenyl groups were synthesized via solution polycondensation of triphosgene with 4, 4'-(bicyclo (2.2.1) hept-5-en-2 yl methylene) bis (2-methoxyphenol) (BPA-NB) or various mol % compositions of BPA-NB and bisphenol-A, respectively. 1H-NMR spectroscopy confirmed the chemical structure and composition of PC-NBs. Inherent viscosity and number-average molecular weight (Mn) values of PC-NBs were in the range 0.44 – 0.64 dL g−1 and 21,800 – 34,100 g mol−1, respectively, indicating the formation of polymers of medium to reasonably high molecular weights. Tough, transparent, and flexible films of PC-NBs could be cast from chloroform solution. X-Ray diffraction studies indicated the amorphous nature of PC-NBs. Glass transition temperature (Tg) values, determined by DSC analysis, of PC-NBs were in the range 154 – 175°C and Tg values increased with the increase in mol % of BPA-NB. The post-polymerization modification of a representative PC-NB was demonstrated using 3,6-diphenyl-1,2,4,5-tetrazine via tetrazine-ene reaction.

High aspect ratio cellulose nanofibrils with low crystallinity for strong and tough films

Cellulose nanofibril (CNF) films with both high strength and high toughness are attractive for applications in energy, packaging, and flexible electronics. However, simultaneously achieving these mechanical properties remains a significant challenge. Herein, a multiscale structural optimization strategy is proposed to prepare high aspect ratio CNFs with reduced crystallinity for strong and tough films. Carboxymethylation coupled with mild mechanical disintegration is employed to modulate the multiscale structure of CNFs. The as-prepared CNFs feature an aspect ratio of >800 and a crystallinity of <60 %. The film prepared using CNFs with a high aspect ratio (~1100) and reduced crystallinity (~54 %) exhibits a tensile strength of 229.9 ± 9.9 MPa and toughness of 22.2 ± 1.4 MJ/m3. The underlying mechanism for balancing these mechanical properties is unveiled. The high aspect ratio of the CNFs facilitates the transfer and distribution of local stress, thus endowing the corresponding film with high strength and toughness. Moreover, the low crystallinity of the CNFs permits the movement of the cellulose chains in the amorphous regions, thereby dissipating energy and finally increasing the film toughness. This work introduces an innovative and straightforward method for producing strong and tough CNF films, paving the way for their broader applications.

Strong and tough semi-crystalline poly(aryl ether nitrile) with low coefficient of thermal expansion

The crystallization of poly (aryl ether nitrile) (PEN) has an essential impact on improving heat resistance, mechanical properties, chemical resistance, and dielectric properties. However, during the synthesis process, high crystallinity PEN is prone to precipitate out, which makes it difficult to carry out the synthesis reaction, which poses a significant challenge to synthesizing high crystallinity and high molecular weight PEN. In this work, hydroquinone (HQ) as the main phenolic monomer and 4,4′-biphenol (BP) as the second phenolic monomer were used to solve the technical difficulties in synthesis by copolymerization. The crystalline PEN with high molecular weight and significant crystallinity was obtained by regulating the molar ratio of BP to HQ. The effects of isothermal heat treatment on its crystalline, mechanical, and thermal properties were investigated. The influence laws of molecular chain structure and heat treatment process on the properties of PEN films were revealed. Among them, when the isothermal treatment temperature was 270 °C and the HQ: BP was 85:15, the mechanical strength reached 130 MPa, and the elongation at break could be up to an astonishing 50 %. Besides, the CTE value from 50 °C–150 °C is 40.84 ppm/°C, which is lower than most thermoplastics. Therefore, PEN with the HQ to BP molar ratio of 85:15 is suitable for large-scale production, providing new crystalline plastic specifications for high-performance special engineering plastics. A crystal bridge-tie chain model is summarized by the properties of HQ/BP-PEN films under different crystallization conditions, which provides an idea for preparing stiff and tough films.

A Stretchable and Tough Graphene Film Enabled by Mechanical Bond.

The pursuit of fabricating high-performance graphene films has aroused considerable attention due to their potential for practical applications. However, developing both stretchable and tough graphene films remains a formidable challenge. To address this issue, we herein introduce mechanical bond to comprehensively improve the mechanical properties of graphene films, utilizing [2]rotaxane as the bridging unit. Under external force, the [2]rotaxane cross-link undergoes intramolecular motion, releasing hidden chain and increasing the interlayer slip distance between graphene nanosheets. Compared with graphene films without [2]rotaxane cross-linking, the presence of mechanical bond not only boosted the strength of graphene films (247.3 vs 74.8 MPa) but also markedly promoted the tensile strain (23.6 vs 10.2 %) and toughness (23.9 vs 4.0 MJ/m3). Notably, the achieved tensile strain sets a record high and the toughness surpasses most reported results, rendering the graphene films suitable for applications as flexible electrodes. Even when the films were stretched within a 20 % strain and repeatedly bent vertically, the light-emitting diodes maintained an on-state with little changes in brightness. Additionally, the film electrodes effectively actuated mechanical joints, enabling uninterrupted grasping movements. Therefore, the study holds promise for expanding the application of graphene films and simultaneously inspiring the development of other high-performance two-dimensional films.

A Stretchable and Tough Graphene Film Enabled by Mechanical Bond

AbstractThe pursuit of fabricating high‐performance graphene films has aroused considerable attention due to their potential for practical applications. However, developing both stretchable and tough graphene films remains a formidable challenge. To address this issue, we herein introduce mechanical bond to comprehensively improve the mechanical properties of graphene films, utilizing [2]rotaxane as the bridging unit. Under external force, the [2]rotaxane cross‐link undergoes intramolecular motion, releasing hidden chain and increasing the interlayer slip distance between graphene nanosheets. Compared with graphene films without [2]rotaxane cross‐linking, the presence of mechanical bond not only boosted the strength of graphene films (247.3 vs 74.8 MPa) but also markedly promoted the tensile strain (23.6 vs 10.2 %) and toughness (23.9 vs 4.0 MJ/m3). Notably, the achieved tensile strain sets a record high and the toughness surpasses most reported results, rendering the graphene films suitable for applications as flexible electrodes. Even when the films were stretched within a 20 % strain and repeatedly bent vertically, the light‐emitting diodes maintained an on‐state with little changes in brightness. Additionally, the film electrodes effectively actuated mechanical joints, enabling uninterrupted grasping movements. Therefore, the study holds promise for expanding the application of graphene films and simultaneously inspiring the development of other high‐performance two‐dimensional films.

Elastic films of single-crystal two-dimensional covalent organic frameworks.

The properties of polycrystalline materials are often dominated by defects; two-dimensional (2D) crystals can even be divided and disrupted by a line defect1-3. However, 2D crystals are often required to be processed into films, which are inevitably polycrystalline and contain numerous grain boundaries, and therefore are brittle and fragile, hindering application in flexible electronics, optoelectronics and separation1-4. Moreover, similar to glass, wood and plastics, they suffer from trade-off effects between mechanical strength and toughness5,6. Here we report a method to produce highly strong, tough and elastic films of an emerging class of 2D crystals: 2D covalent organic frameworks (COFs) composed of single-crystal domains connected by an interwoven grain boundary on water surface using an aliphatic bi-amine as a sacrificial go-between. Films of two 2D COFs have been demonstrated, which show Young's moduli and breaking strengths of 56.7 ± 7.4 GPa and 73.4 ± 11.6 GPa, and 82.2 ± 9.1 N m-1 and 29.5 ± 7.2 N m-1, respectively. We predict that the sacrificial go-between guided synthesis method and the interwoven grain boundary will inspire grain boundary engineering of various polycrystalline materials, endowing them with new properties, enhancing their current applications and paving the way for new applications.

Tough and biodegradable C-lignin cross-linked polyvinyl alcohol supramolecular composite films with closed-looping recyclability

Catechyl lignin (C-lignin) is a unique natural biopolymer that is considered to be the best alternative to conventional lignin due to its linear homogeneous molecular structure. Based on the structural properties of C-lignin, the development of a new biodegradable plastic to replace traditional petroleum-based plastics is a sustainable route. However, the maximum filling fraction of lignin is required to achieve excellent biodegradability of lignin-based bio-plastics, yet resulting in decreased mechanical strength of composites. Herein, we report a novel strategy to fabricate a closed-loopling recyclability supramolecular composite films through casting and dry molding process of intermolecular covalent-noncovalent cross-linking networks with polyvinyl alcohol by the epoxidation of C-lignin. The intermolecular cross-linking mechanism analyses reveal that the resultant bio-material not only display improved mechanical properties (maximum tensile strength of 133.5 MPa and strain at break of 690.2 %), but also show UV-resistant, antimicrobial, thermally stable, and rapid biodegradable properties. Notably, the fabricated films demonstrate the characteristics of closed-loop recyclability, which paves a new way toward rational design of bioplastics using renewable lignin. These integrated properties make the lignin-based biocomposites a promising alternative to traditional plastics.

An ingenious synergistic solid lubricant of copper and graphite for exceptional wear resistance of the SCF/PTFE/PEEK composite

In this work, the conventional short carbon fiber (SCF)/polytetrafluoroethylene (PTFE)/polyetheretherketone(PEEK) (SCF/PTFE/PEEK) composite was elected as the matrix, copper and graphite micron flakes were further blended to prepare PEEK self-lubricating composites. At a pressure of 12 MPa and a speed of 0.5 m/s, with a graphite content of 7.5 wt% and copper of 2.5 wt% (Gr7.5Cu2.5), the composite exhibited a COF of 0.23 and the lowest wear rate of 4.1 × 10−7 mm3/Nm. Physicochemical analysis of the worn surface of the steel ring revealed that the introduction of appropriate amounts of copper facilitated the tribo-physicochemical reaction during the rubbing process, which favored the formation of a thin and tough transfer film of Gr7.5Cu2.5 on the worn surface of the steel ring.

Fluorescent carbon dots in situ polymerized biodegradable semi-interpenetrating tough hydrogel films with antioxidant and antibacterial activity for applications in food industry

A flexible, antioxidant, biodegradable, and UV-resistant polymeric nanocomposite hydrogel with heteroatom-doped carbon dots (CDs) has been fabricated using a simple one-step in situ free radical gelation process. The hydrogel formation and their physico-mehcanical characteristics have been assessed by rheology, uniaxial tensile and compression testing. The water uptake behaviour of the hydrogels is controlled by the CDs by manipulating their internal morphology and porosity. The porous nature of the hydrogels has been found from their scanning electron microscopic images which are also supported by their anomalous diffusion-based transport mechanism. The rheological signatures of the hydrogels show delayed network rupturing due to the secondary physical crosslinking alleviated by CDs. Moreover, CDs are directly influencing the permeabilites (oxygen and moisture) by lowering the values compared to their neat hydrogel films which are essential for a packing material. The biodegradability of the hydrogel films showed gradual weight loss (<75 %) within 3 weeks. The hydrogel films also have been qualified to be acted as antibacterial and antioxidant material. The shelf-life and non-leaching of CDs from gel matrices are also performed which shows its excellent capability to be used as a potential antibacterial, biodegradable, antioxidant alternative packaging material in food sectors.

A Stretchable and Tough Conductive Elastic Film for Multifunctional Flexible Strain Gauges

AbstractAs an important branch of modern science and technology, flexible sensor combines the functions of traditional sensors with the characteristics of flexible materials to meet the needs of modern electronic devices for lightweight, flexible and wearable characteristics. However, flexible sensors are faced with problems such as poor stability and weak anti‐interference ability in extreme environments. Here, a strategy of combining thermoplastic polyurethane and conductive carbon black is adopted to obtain conductive elastic film with good conductivity and excellent mechanical properties (TPU@CB film). TPU@CB film exhibits very good mechanical strength (8 MPa). When TPU@CB film is assembled into a sensor, it exhibits wide detection range (600%), low detection limit (0.05%) and short response time (15 ms). Notably, the TPU@CB film demonstrates clear detection capabilities for both ECG and EMG signals of the human body when utilized as an electrode patch. Thanks to lithography, TPU@CB film is machined into strain gauge shape. TPU@CB strain gauge achieves a high signal‐to‐noise ratio and can detect a wide range of frequency vibrations from 0 to 900 Hz, as well as accurately detect the speed of the motor. This provides a feasible way to promote the development of flexible electronics.

High-throughput development of tough metallic glass films.

Fast development of metallic glass films with high toughness has been a long-sought goal of humankind in view of their superior properties and great potential for application in the field of soft electronics. However, until now, there has been no effective experimental strategy because of the lack of suitable and precise toughness measurement technology. In the present work, we introduced a feasible route for developing tough metallic glass films using combinatorial material library preparation and high-throughput toughness measurement via nanoindentation. Based on this route, tough metallic glass films for the quaternary Zr-Ti-Cu-Al system were successfully screened out. The corresponding electron work function map was detected to uncover the physical mechanism for the composition dependence of toughness. In addition, the preliminary assessments of the screened tough metallic glass films as strain-sensing materials were also conducted. Our current research not only provides a versatile toolbox for high-throughput development of tough metallic glass films, but also exemplifies their potential as strain-sensing materials.

Norbornenyl-pendant aromatic (co)poly(ether ether ketone)s

4, 4'-(Bicyclo (2.2.1) hept-5-en-2 yl methylene) bis (2-methoxyphenol) (BPA-NB) was utilized as a step-growth monomer for the synthesis of (co)poly(ether ether ketone)s (PEEK-NBs) via nucleophilic aromatic substitution polycondensation. A homo and five PEEK-NBs were synthesized by polycondensation of 4, 4'-difluorobenzophenone with BPA-NB and various compositions of BPA-NB and bisphenol-A, respectively. 1H NMR spectroscopy confirmed the chemical structure and composition of PEEK-NBs. Inherent viscosity and number-average molecular weight values of PEEK-NBs were in the range 0.64 to 0.78 dL g−1 and 62,670 to 84,470 g mol−1, respectively, indicating the formation of polymers of reasonably high molecular weight. It was easy to dissolve PEEK-NBs in common organic solvents such as chloroform, dichloromethane, and tetrahydrofuran. Tough, transparent, and flexible films of PEEK-NBs could be cast from chloroform solution. X-Ray diffraction studies indicated amorphous nature of PEEK-NBs. Glass transition temperature (Tg) values, determined by DSC analysis, of PEEK-NBs were in the range 163 to190 °C and Tg values increased with the increase in mol % of BPA-NB. The post-polymerization modification of a representative PEEK-NB was demonstrated using two azido compounds, namely, 4-(azidomethyl)-7-methoxy-2H-chromen-2-one and 9-(azidomethyl)anthracene, via metal-free azide-alkene 1,3-dipolar cycloaddition reaction to obtain copoly(ether ether ketone)s appended with coumarinyl and anthracenyl moieties, respectively.

Tough, flexible and oil-resistant film from sonicated guar gum and cellulose nanofibers for food packaging

Utilizing renewable and locally available raw materials in flexible film production with modifications and reinforcements is crucial in the fight against plastic pollution. This study investigates the use of sonicated guar gum for film production with reinforcement from cellulose nanofibers derived from sugarcane bagasse. Cellulose nanofibers were obtained with a yield of 46.6% and a purity of 95%, exhibiting a crystallinity of 75.64% and thermal stability up to 323 °C. Films were prepared using sonicated guar gum under varying process conditions (time: 0–12.5 min, amplitude: 50,100%), and the film with optimal properties was chosen for reinforcement with varying mass percentages of nanofibers. The film with 0.01 g of nanofiber reinforcement demonstrated significant improvements in tensile strength (23.04 MPa), elongation (39.19%), ultimate modulus (134.94 MPa), and a reduction in water vapor permeability (1.76 × 10−10 gm/m2Pas). This film also showed exceptional resistance to oil permeation, making it a promising candidate for packaging oil-based foods.

Boosting fast electrode reaction kinetics of silicon suboxide anodes by fluoroethylene carbonate-based electrolyte

The growing demand for electric vehicles has led to an urgent need for higher-energy-density batteries. Silicon (Si) has been regarded as an alternative to graphite as an anode material owing to its high theoretical capacity. Nevertheless, the large volume change in Si during repeated charge/discharge causes serious particle fracture, leading to rapid capacity degradation. Silicon suboxide (SiOx) anodes show better cycling performance than Si because of their alleviated volume variation, yet still have unsatisfactory electrode reaction kinetics. Herein, fluoroethylene carbonate (FEC)-based electrolyte is proposed to enhance the electrochemical properties of SiOx anodes. A higher specific capacity of ∼1500 mAh g−1 at 0.5 A g−1 and an excellent rate capability of ∼1050 mAh g−1 at 4 A g−1 are obtained for the SiOx anode, which ensures an 83.5% capacity retention of SiOx||LiFePO4 cells after 300 cycles. The theoretical calculations and experimental studies reveal that FEC forms a weakly solvating electrolyte, enabling easier Li-ion desolvation and fast electrode reaction kinetics. Moreover, FEC reinforces the Li+-anion coordination owing to its weak solvating capability, thus a LiF-rich electrode/electrolyte interphase is formed through the co-decomposition of FEC and PF6− anions, leading to a tough SEI film formation with rapid ionic conductivity and good mechanical property.

Flame‐resistant and tough polyvinyl alcohol film with ultraviolet‐absorbing capacity

AbstractFireproofing the polyvinyl alcohol (PVA) membrane is an essential and urgent reinforcement to ease the restriction in flame‐resistant requirements. The traditional method by the physical and heterogenous introduction of a large number of metal hydroxides, halogenated and organic compounds efficiently enhance the flame‐retardancy but severely weakens the biocompatibility, mechanical strength, and transparency of PVA membranes. In this work, two bio‐extracted compounds, phytic acid (PA) and creatine (CR) are employed to construct a fireproof, tough and transparent PVA membrane. The LOI of the PVA/PACR membrane increases from 18% to 30% and reaches a V–0 grade in UL‐94 testing. Meanwhile, the mechanical strength receives 20% reinforcement due to a chemical crosslinking between PVA, PA, and CR. Intriguingly, unsaturated chemical bonds from PA and CR endow a favorable UV‐absorbing capacity to the PVA membrane, which will benefit the anti‐aging and food freshness retaining demands in advanced packaging applications.

Graphene oxide modified tung oil-based vinyl ester coating with improved anti-corrosion performance

Vinyl ester resin (VER) has been regarded as one of effective anti-corrosive resins, which is commonly used in anti-corrosion coating fields. However, the barrier effect of VER-based films against the corrosion medium is seriously reduced due to the inevitable generation of pores and cracks during the VER-based film formation process. In this work, the modified lamellar graphene oxide (GO560) nanoparticles used as functional fillers are introduced into the VER-based film matrix to address the above issue. Herein, GO nanoparticles are modified by epoxy-terminated silane coupling agent (KH560) to improve their dispersibility and hydrophobicity. And then the GO560 nanoparticles are bridged with VER through the tung oleic acid maleic anhydride (TOAMA). The study results of stand test, Fourier infrared spectrum (FTIR), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) indicate that the ring opening reaction of carboxylic anhydride (TOAMA) with epoxy groups from GO560 nanoparticles and epoxy resin assists in the good dispersibility of GO560 nanoparticles in the VER composite film matrix. Moreover, the electrochemical impedance measurement shows that the low-frequency impedance of GO560/VER films (7.08 × 1010 Ω cm2) is 4 orders of magnitude higher than that of Blank/VER film (1.11 × 107 Ω cm2) after 100-day immersion in 3.5 wt% NaCl solution, which implies the obviously improvement of corrosion resistance for VER-based film by introducing GO560 nanoparticles. This study provides a promising method for uniformly dispersing the epoxidized GO nanosheets by the bridged linkage effect of bio-based materials into VER-based film, and then construct multifunctional nanosheets-VER composite tough films with the favorable and long-lasting anti-corrosion performance, which have the great potential in the marine anti-corrosion application including ships and marine engineerings.

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G') was significantly greater than the viscous modulus (G″) for the entire frequency range.