Tough Films Research Articles

Recyclable heterogeneous palladium-catalyzed Heck coupling polycondensation of bis(acrylamide)s with aromatic diiodides towards polycinnamamides

A new and practical method for the preparation of high molecular weight polycinnamamides has been developed through a heterogeneous palladium-catalyzed Heck coupling polycondensation of bis(acrylamide)s with aromatic diiodides. The polymerization proceeded smoothly in DMF at 100 °C in the presence of a magnetic nanoparticles-anchored bidentate phosphine-palladium(II) acetate complex [Fe3O4@SiO2-2P-Pd(OAc)2] and tributylamine, yielding a series of polycinnamamides with inherent viscosities up to 0.89 dL/g and a low level of palladium residue (below 10 ppm). The polycinnamamides obtained were quite soluble in dipolar aprotic solvents and had glass transition temperatures ranging from 221 to 269 °C and 10% weight loss temperatures ranging from 437 to 458 °C in nitrogen. These polymers could afford transparent and tough films by solution-casting with tensile strengths of 59.6–82.8 MPa, tensile moduli of 1.78–2.12 GPa, and elongations at break of 7.5–12.5%. The Fe3O4@SiO2-2P-Pd(OAc)2 catalyst can be conveniently separated from the polymer and recovered by simply using an external magnetic field, and recycled at least eight times without apparent decrease in catalytic efficiency.

New transparent and thermally stable cardo poly(ether imide)s derived from 10,10-bis[4-(4-amino-2-pyridinoxy)phenyl]-9(10H)-anthrone

A new diamine bearing flexible ether, rigid pyridine, and bulky anthrone pendent group, 10,10-bis[4-(4-amino-2-pyridinoxy)phenyl]-9(10 H)-anthrone (BAPPA), was prepared in three steps from anthrone. BAPPA was reacted with six conventional aromatic dianhydrides in N, N-dimethylacetamide (DMAc) to form the corresponding new poly(ether imide)s (PEIs) via the poly(ether amic acid) (PEAA) precursors with inherent viscosities ranging from 0.85 dL g−1 to 1.26 dL g−1 and thermal imidization. All the PEAAs could be cast from DMAc solution and thermally converted into transparent, flexible, and tough PEI films with tensile strength of 72.2–112.4 MPa, tensile modulus of 1.8–2.1 GPa, and elongation at break of 10–18%. These PEIs were predominantly amorphous and displayed excellent thermal stability with the glass transition temperature of 290–388°C, the 5% weight loss temperature of 480–514°C, and the residue of 68–43% at 800°C in nitrogen. The PEIs derived from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 4,4′-hexafluoroisopropylidenediphathalic anhydride exhibited excellent solubility in organic solvents such as N-methyl-2-pyrrolidinone, DMAc, N, N-dimethylformamide, pyridine, and even in tetrahydrofuran. Meanwhile, these PEIs also exhibited high optical transparency with the ultraviolet cutoff wavelength in the 374–427 nm range and the wavelength of 80% transparency in the range of 468–493 nm.

Synthesis and characterization of two novel poly(amide-imide)s containing pendent (5-(4,5-diphenyl-1H-imidazol-2-yl)furan-2-yl)phenyl moieties and natural amino acids linkages for adsorption of Cu(II)

Two novel optically active poly(amide-imide)s (PAI)s were prepared by the direct polycondensation of diamine, 3,5-diamino-N-(4-(5-(4,5-diphenyl-1H-imidazol-2-yl)furan-2-yl)phenyl)benzamide with two optically active dicarboxylic acids such as N,N′-(pyromellitoyl)-bis-l-phenylalanine and N,N′-(4,4′-carbonyldiphthaloyl)-bis-l-phenylalanine in molten tetrabutylammonium bromide (TBAB) as a green medium with triphenyl phosphite as condensing agent. The diamine was synthesized via the direct condensation of 2-[5-(4-aminophenyl)furan-2-yl]-4,5-diphenyl-1H-imidazole with 3,5-dinitrobenzoyl chloride and following reduction in the dinitro compound. The resulting PAIs had inherent viscosities of 0.38 and 0.35 dL g−1. The PAIs were dissolved in polar organic solvents, such as NMP, DMAc, DMSO and DMF at room temperature. These polymers were solution-cast from DMAc solution into transparent, flexible and tough films. Wide-angle X-ray measurement exhibited that the PAIs were amorphous. These PAIs had 10% weight loss temperatures of 427 and 440 °C under nitrogen atmosphere. The polymer films had a tensile strength of 102 and 108 MPa and a tensile modulus of 2.2 and 2.3 GPa. The adsorption capability of one of the PAIs for removal Cu2+ from aqueous solutions was tested at pH 5.

High optical transparency, low dielectric constant and light color of organosoluble fluorinated polyimides based on 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone

A new aromatic diamine bearing ether, trifluoromethyl and anthrone groups, 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone (BATFPA) was prepared in three steps from anthrone. BATFPA was reacted with six conventional aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to form the corresponding cardo fluorinated polyimides (PIs) via the poly(amic acid) (PAA) precursors with inherent viscosities ranging from 0.82 to 1.18 dL/g and thermal imidization. All the PAAs could be cast from DMAc solution and thermally converted into transparent, flexible and tough PI films with tensile strength of 63.5–101.7 MPa, tensile modulus of 1.94–2.85 GPa and elongation at break of 3.7–13.6%. The resulting PIs were predominantly amorphous and exhibited good solubility in dipolar solvents such as DMAc, N,N-dimethylformamide and N-methyl-2-pyrrolidinone at room temperature. In particular, the PI derived from 4,4′-hexafluoroisopropylidenediphthalic anhydride was even soluble in tetrahydrofuran. These new PIs displayed excellent thermal stability with Tg of 259–329 °C, 5% weight loss temperature (Td5) of 516–530 °C and the residue of 57–64% at 800 °C in nitrogen. Meanwhile, these PIs also had low moisture absorptions (0.36–0.83%), low dielectric constants (2.35–2.96 at 1 MHz), good optical transparency with cutoff wavelengths of ultraviolet–visible absorption at 336–408 nm and more than 80% transmittance at 600 nm.

Soluble copolyimides containing 4,4′-isopropylidenedicyclohexanol (HBPA) isomer units: Synthesis, characterization, thermal, mechanical, and optical properties

In this work, 4,4′-isopropylidenedicyclohexanol (HBPA)-based dinitro isomers mixture (H″BPBN and H′BPBN) was synthesized and separated, and the structures of dinitro isomers were confirmed by differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy. A series of copolyimides were prepared from diamino monomers with different percentages of novel diamine H″BPDA and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride via a conventional two-step procedure. All the copolyimides could afford flexible, tough, and transparent films with transmittance no less than 73% at 450 nm, which was attributed to the fact that nonplanar alicyclic diamine and the bulky and weakly polarizable trifluoromethyl hampered the formation of charge-transfer complex. Moreover, all the copolyimides were soluble not only in polar solvents such as N,N-dimethylformamide but also in low-boiling-point solvents such as dichloromethane, which was related to the fact that the existence of alicyclic diamine and bulky trifluoromethyl decreased the intermolecular force. In addition, the conformation effects of H″BPDA and H′BPDA on the aspects of thermal, mechanical, optical, and soluble performance of copolyimides were investigated and their structure–property relationships were discussed in detail.

Insight into the lubricating mechanism for alkylimidazolium phosphate ionic liquids with different alkyl chain length

Abstract Three kinds of alkylimidazolium phosphate ionic liquids (ILs) with different alkyl-chain length of cations are synthesized and their friction-reducing and antiwear properties for steel/steel sliding pairs are enhanced with the increasing of the alkyl-chain length. The lubricating mechanism can be attributed to two aspects: on the one hand, the contact electrical resistance (ECR), corrosion, electrochemical test results reveal that ILs with longer alkyl-chains exhibit better adsorption ability; on the other hand, the XPS and EDS analysis results of wear scars indicate that the active elements (such as N and P) are more liable to have tribochemical reactions with the substrate surfaces and forming more tough tribochemical films.

Novel preparation of poly(arylene ether sulfone amide)s via supported palladium-catalyzed carbonylative polymerization

Two new aromatic diiodides with ether–sulfone linkages were synthesized via a one-step procedure. A series of poly(arylene ether sulfone amide)s were synthesized by a supported palladium-catalyzed polycondensation of aromatic diiodides having ether–sulfone linkages, aromatic diamines, and CO. Polycondensation reactions were conducted in N,N-dimethylacetamide using a magnetic nanoparticles-bound palladium(II) complex [Fe3O4@SiO2-2P-PdCl2] as the catalyst and 1,8-diazabicycle[5,4,0]-7-undecene as the base at 120 °C, yielding poly(arylene ether sulfone amide)s having inherent viscosities of 0.43–0.77 dL/g. The resulting polymers were soluble in polar aprotic solvents and showed glass transition temperatures in the 204–265 °C range, with 10% weight losses occurring at temperatures above 456 °C in nitrogen. Most of the polymers afforded transparent and tough films by solution-casting with tensile strengths of 71.8–82.2 MPa, Young’s moduli of 1.77–2.35 GPa, and elongations at break of 9.3–13.4%. More importantly, this supported palladium catalyst can facilely be separated from the product by simply using an external magnetic field and reused at least seven times with almost consistent activity.

A new cardo bisphenol monomer containing pendant azido group and the resulting aromatic polyesters

ABSTRACTExpanding on our strategy to synthesize aromatic step‐growth polymers containing pendant clickable azido groups via functional monomer approach, we have now designed and synthesized a new cardo bisphenol, viz., 2‐(2‐azidoethyl)‐3, 3‐bis(4‐hydroxyphenyl) isoindolin‐1‐one (PPH‐N3). PPH‐N3 was conveniently synthesized starting from commercially available phenolphthalein by a three‐step route in an overall yield of 65% using simple organic transformations. Aromatic (co)polyesters bearing pendant azido groups were synthesized by low‐temperature solution polycondensation of PPH‐N3 or different molar ratios of PPH‐N3 and bisphenol‐A (BPA) with aromatic diacid chlorides in dry dichloromethane in the presence of triethylamine (TEA) as a base. The formation of medium to reasonably high‐molecular‐weight (co)polyesters was evidenced from intrinsic viscosity and number‐average molecular‐weight measurements that were in the range 0.52–0.85 dL/g and 16,700–28,200, respectively. Tough, transparent, and flexible films could be cast from chloroform solutions of these (co)polyesters. (Co)polyesters were characterized using FTIR, 1H NMR, 13C NMR spectroscopy, XRD, and TGA. The thermal curing reaction of (co)polyesters involving decomposition of azido groups was studied by DSC analysis. The chemical modification of a representative copolyester containing pendant azido groups was carried out quantitatively using catalyst‐free azide‐maleimide cycloaddition reaction with two maleimides, namely, N‐methylmaleimide and N‐hexylmaleimide. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1516–1526

Soluble Polyimides Bearing (cis, trans)-Hydrogenated Bisphenol A and (trans, trans)-Hydrogenated Bisphenol A Moieties: Synthesis, Properties and the Conformational Effect

In this work, hydrogenated bisphenol A (HBPA) based dinitro mixed isomers (1a′ and 1a) were synthesized and separated via vacuum distillation under the monitor of DSC and 1H NMR. Corresponding diamines (2a′ and 2a) were separately polycondensed with five commercial dianhydrides via a two-step thermal imidization to obtain PI-(1′-5′) and PI-(1-5). All the polyimides could afford flexible, tough, and transparent films, and most of them were readily soluble not only in common polar solvents like DMAc, but also in low boiling point solvents such as chloroform. 1H NMR spectra of the polyimides demonstrated that HBPA moiety showed no conformation changes during the preparation of polymers. For a given dianhydride, PI-(1-5) exhibited better thermal stability than that of PI-(1′-5′), this can be attributed that the equatorial, equatorial C–O in PI-(1-5) promoted denser and more regular molecular chain stacking, as can be evidenced by the WAXD and geometric optimization results. Additionally, when the dianhydride was ODPA, BPADA or 6FDA, no apparent difference was found in either the transmittance or solubility between two series of polyimides, which could be attributed that twisted and flexible ether linkages, as well as bulky substituents, led to the “already weakened” inter- and intramolecular CT interaction and cohesive force. However, when it came to rigid and stiff dianhydride, e.g., BPDA, PI-3′ took an obvious advantage over PI-3 in transmittance and solubility, which was possibly owed to the larger molecular chain d-spacing imparted by equatorial, axial C–O. An overall investigation of PI-(1′-5′) and PI-(1-5) on aspects of thermal, mechanical, morphological, soluble and optical performance values was carried out, and the conformation effects of HBPA isomers on the properties of two series of polyimides were discussed in detail.

Fast and simple construction of composite films with renewable Eucommia ulmoides gum and Poly(ε-caprolactone)

Eucommia ulmoides gum (EUG) and Poly(ε-caprolactone) (PCL), a degradable, promising and “green” feedstock, can be used to fabricate composite films by a rapid and simple solution casting method, which have characteristics of degradability, hydrophobicity, strength, and toughness. Herein, EUG was extracted with petroleum ether from seed coats of Eucommia ulmoides and characterized with Fourier transform infrared (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). The FT-IR and NMR revealed that the construction of the EUG and PCL of composite films are a physical blending process. Besides, the addition of PCL effectively enhances the thermal stability of composite films. The concentration of PCL is 0.84 wt% in composite film (P0.84 wt%), which exhibits an excellent elongation at break and energy density at break of 514.3% and 106.4 MJ/m3, respectively. The maximum tensile strength of the resultant film is 1.8 times higher than that of the control film. The hydrophobicity and water vapor barrier property of P0.84 wt% film is increased by 26.6% and 84.0%, respectively, than that of the control film. It is believed this work provided a rapid and simple strategy to fabricate degradable, strong, and tough film.

Origami-Inspired Fabrication: Self-Folding or Self-Unfolding of Cross-Linked-Polyimide Objects in Extremely Hot Ambience

A methodology that integrates a folding step into the conventional poly(amic acid)/polyimide film fabrication scheme is developed. It enables fabricating cross-linked polyimide (XCP2) films into a host of complex-shaped objects. Particularly unprecedented is that these origami (3D) objects can be unfolded into a 2D temporary shape under externally applied stress at T ∼ Tg and remain in the free-standing, 2D configuration at room temperature until spontaneously returning to the original 3D configuration at T > 200 °C. This 3D/2D/3D cycle can be repeated >20× without showing any sign of fatigue, as exemplified by a cubic box that shows visually no dimensional change after each cycle, and even after having been immersed in a 215 °C oil bath for 3 days. The enabling materials are two series XCP2s that are cross-linked by either a phosphine oxide-containing triamine (POTAm) or a trianhydride (POTAn). These cross-linked polyimides form tough and creasable films that possess ∼100% shape memory recovery and 99% shape memory fixity and withstand over 100 fatigue-prone, strain-stress-temperature cycles, while the linear version LCP2 film exhibits much lower shape memory recovery and fails after only 7 cycles.

Developing strong and tough carbon nanotube films by a proper dispersing strategy and enhanced interfacial interactions

A new approach for making carbon nanotube (CNT) films that are both strong and tough is detailed in this paper. Aqueous dispersions of long CNTs were first obtained by dispersing CNT arrays with heights of about 200 μm in deionized water with the help of polyvinylpyrrolidones (PVPs) and polydopamines (PDAs). CNT films were then obtained by vacuum-assisted filtration of CNT dispersions. The tensile strength and toughness of the composite films can be as high as 143.5 MPa and 5.0 MJ/m3, respectively, which was 330.7% and 213.8% higher than CNT films made without using PVPs and PDAs. The underlying mechanism of PVPs and PDAs induced CNT film strengthening and toughening was revealed through preliminary molecular dynamics simulations, which indicated that the hydrogen bonds between the PVPs and PDAs enhanced the strength of the film, and these bonds can cyclically break and reform, making CNT films tougher. The strategy proposed here can also be applied to making other nano-materials based strong and tough macro-assemblies.

Aromatic polyesters containing pendant azido groups: Synthesis, characterization, chemical modification and thermal cross-linking

A partially bio-based bisphenol containing pendant azido group viz., 4,4′-(5-azidopentane-2,2-diyl) diphenol (AZBPA) was synthesized starting from 4,4′-bis (4-hydroxyphenyl) pentanoic acid. AZBPA was reacted with isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) and a mixture of IPC/TPC (50:50 mol%) by phase transfer-catalyzed interfacial polycondensation route to obtain aromatic polyesters containing pendant azido groups. Copolyesters containing pendant azido groups were also synthesized by polycondensation of different molar proportions of AZBPA and commercially available 4,4′-(1-phenylethane-1,1-diyl) diphenol (BPA-AP) with IPC. Inherent viscosities and number average molecular weights of (co)polyesters were in the range 0.85–1.64 dL/g and 58,900–190,400, respectively, indicating the formation of reasonably high molecular weight polymers. Tough, transparent, and flexible films could be cast from chloroform solutions of these polyesters. X-Ray diffraction analysis showed that (co)polyesters were amorphous in nature. (Co)polyesters were characterized using FT-IR, 1H NMR spectroscopy, XRD, TGA and DSC analysis. The chemical modification of a representative copolyester containing pendant azido groups was carried out quantitatively using copper-catalyzed azide-alkyne cycloaddition (CuAAC) with two alkynes viz., phenyl acetylene (PA) and ethynyl-4-nitrobenzene (ENB). Additionally, (co)polyesters containing pendant azido groups were thermally cross-linked (170 °C/12 h) leading to the formation of network structures based on azide to nitrene decomposition and subsequent reactions on polyester backbone. The selected cross-linked polyesters were characterized by stress-strain measurements. The cross-linked polymers exhibited higher tensile strength and Young’s modulus and lower % elongation at break compared to corresponding pristine polyesters containing pendant azido groups.

Ultrahigh Tough, Super Clear, and Highly Anisotropic Nanofiber-Structured Regenerated Cellulose Films.

While tremendous efforts have been dedicated to developing environmentally friendly films made from natural polymers and renewable resources, in particular, multifunctional films featuring extraordinary mechanical properties, optical performance, and ordered nanostructure, challenges still remain in achieving all these characteristics in a single material via a scalable process. Here, we designed a green route to fabricating strong, super tough, regenerated cellulose films featuring tightly stacked and long-range aligned cellulose nanofibers self-assembled from cellulose solution in alkali/urea aqueous systems. The well-aligned nanofibers were generated by directionally controlling the aggregation of cellulose chains in the hydrogel state using a preorientation-assisted dual cross-linking approach; i.e., a physical cross-linking was rapidly introduced to permanently reserve the temporarily aligned nanostructure generated by preorienting the covalent cross-linked gels. After a structural densification in air-drying of hydrogel, high strength was achieved, and more importantly, a record-high toughness (41.1 MJ m-3) in anisotropic nanofibers-structured cellulose films (ACFs) was reached. Moreover, the densely packed and well-aligned cellulose nanofibers significantly decreased the interstices in the films to avoid light scattering, granting ACFs with high optical clarity (91%), low haze (<3%), and birefringence behaviors. This facile and high-efficiency strategy might be very scalable in fabricating high-strength, super tough, and clear cellulose films for emerging biodegradable next-generation packaging, flexible electronic, and optoelectronic applications.

Strong Wet Adhesion of Tough Transparent Nanocomposite Hydrogels for Fast Tunable Focus Lenses.

Tough hydrogel adhesives that can bond strongly to wet surfaces have shown great potential in various applications. However, it still remains a challenge to develop the adhered hydrogels integrated with strong wet adhesion, high transparency, exceptional mechanical properties, and fast self-recovery. Herein, tough nanocomposite hydrogels demonstrating high tensile strength, high transparency, and fast self-recovery are reported. The strong wet adhesion between two tough hydrogel films can be realized by introducing chemical bridging across the hydrogel-hydrogel interface, while the interfacial adhesion energy and shearing adhesion strength are up to 2216 J m-2 and 385 N m-1, respectively. The strong adhesion and superior toughness of our hydrogels enable their reassembly capability to produce stretchable sealed balloons that can endure high air pressure without leakage. Most interestingly, the combination of excellent sealability and high transparency also allows our hydrogel balloons to turn into hydraulically driven fast tunable focus convex lenses, which is first reported here for hydrogel lenses. The hydrogel adhesives may open up the door to develop soft sealed containers and intelligent optical devices.

Thermodynamic and hydrodynamic fluorescence emission behaviors of polydiphenylacetylenes with different size of substituents

Four polydiphenylacetylenes (PDPAs: C3, C6, C9, C12) containing different size of trialkylsilyl groups (C3: trimethyl; C6: triethyl; C9: trin-propyl; C12: trin-butyl) were prepared and their thermodynamic and hydrodynamic fluorescence (FL) emission behaviors were investigated and discussed in relation to physicochemical properties such as fractional free volumes (FFVs) and solubility parameters. These polymers existed in glassy state at room temperature to provide quite tough films. Also, the polymers were amorphous and the intermolecular distance increased with the molecular size of substituent. As the substituent became larger, the FFV of the polymer decreased and the solubility parameter increased. At the same time, the FL quantum efficiency (FLQE) increased both in the toluene solution and film. Exceptionally, however, C3 exhibited a quite high FLQE in solution despite the smallest substituent because of the lower affinity of the polymer with the solvent. When the polymers were heated both in solution and film, the FL change according to temperature became less significant as the substituent became larger. Even in this event, C3 did not follow the rule. C3 exhibited the least significant FL change in film despite the smallest substituent owing to the dense space occupied by the polymer main chains as known from the largest FFV and the shortest intermolecular distance. On the other hand, when the polymers were dissolved in hydrocarbons or swollen in alcohols, the FL change according to viscosity of the solvents became less significant as the substituent became larger. However, as with the thermodynamic FL emission behavior, C3 film showed an exceptionally less remarkable FL change despite the smallest substituent owing to the much larger difference in solubility parameter between the polymer and alcohol.

Numerical modeling of essential work of fracture on ductile polymeric films

Essential work of fracture method has been successfully used to characterize the fracture behavior of ductile polymeric films. The observed essential and non-essential fracture process zones are related to the toughness of the films. Three-dimensional finite element method (FEM) modeling has been carried out in this study to elucidate the film fracture process based on the essential work of fracture concept. Experimental observation on a model linear low-density polyethylene (LLDPE) blown film was used to validate the FEM model. The numerical model facilitates an in-depth understanding of the development of stress and strain fields and the fracture process zones at different loading steps. The FEM findings show that film thickness and ligament length have significant influence on the development of stress and strain fields at and around the ligament area. Furthermore, the numerical analysis reveals how various material properties, such as yield stress and strain hardening slope, can influence the development of fracture process zones. Usefulness of FEM modeling for developing tough polymeric films is discussed.

Organosoluble, low dielectric constant and highly transparent fluorinated pyridine-containing poly(ether imide)s derived from new diamine: 4-(4-trifluoromethyl)phenyl-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine

A new aromatic diamine, 4-(4-trifluoromethyl)phenyl-2,6-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]pyridine, was synthesized by a modified Chichibabin reaction of 4-(4-nitro-2-trifluoromethylphenoxy)acetophenone with 4-triflouromethylbenzaldehyde, followed by catalytic reduction. A series of fluorinated pyridine-containing aromatic poly(ether imide)s (PEIs) were prepared from the diamine monomer with various aromatic dianhydrides via conventional two-step thermal imidization method. The resulting PEIs had inherent viscosities values of 0.68–0.90 dL/g, and could be cast and thermally converted into transparent, flexible, and tough polymer films. These PEIs were predominantly amorphous, had good solubility in common solvents such as NMP, DMAc and m-cresol at room temperature, and displayed excellent thermal stability with the glass transition temperatures of 258–315 °C, the temperatures at 5% weight loss of 550–585 °C, and the residue of higher than 55% at 750 °C in nitrogen. Moreover, the PEIs films showed outstanding mechanical properties with tensile strengths of 74.8–103.5 MPa, tensile moduli of 1.08–1.45 GPa, and elongations at break of 10.6–24.4%. These PEIs also exhibited low dielectric constants of 2.81–2.98 (1 MHz) and water uptake 0.39–0.68%, as well as high optical transparency with the UV cutoff wavelength in the 350–378 nm range and the wavelength of 80% transparency in the range of 412–510 nm.

Tough, strong, and biodegradable composite film with excellent UV barrier performance comprising soy protein isolate, hyperbranched polyester, and cardanol derivative

Tough and biodegradable soy protein isolate film with excellent UV barrier performance by hyperbranched polyester, and cardanol derivative.

Sustainable and tough polyurethane films with self-healability and flame retardance enabled by reversible chemistry and cyclotriphosphazene

Self-healable, flame-retardant, recyclable, and robust polyurethane films were enabled by thermally driven Diels–Alder chemistry and cyclotriphosphazene.