Stretchable Ionic-Liquid-Based Gel Polymer Electrolytes for Lithium-Ion Batteries

Stretchable cross-linked gel polymer electrolytes (C-GPEs) have been fabricated through electron-beam irradiation (EBI) of poly­(vinylidene fluoride-<i>co</i>-hexafluoropropylene) [P­(VDF-<i>co</i>-HFP)]/triallyl isocyanurate (TAIC) blend films followed by adsorption of the ionic liquid 1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([EMIm]­[TFSI]). It was found that polymer films containing 5 wt % cross-linker exhibit an excellent IL uptake value of 3.0 when irradiated at 75 kGy. The prepared C-GPEs have a high ion conductivity of 1.4 mS/cm at room temperature compared with a value of 0.7 mS/cm for P­(VDF-<i>co</i>-HFP)/IL (1/3, m/m) blend gel. Morphological measurements indicate interconnected nanoporous structures in the films that can provide effective channels for ion immigration. Moreover, the C-GPEs show a high tensile strength of 10.6 MPa and an excellent elasticity, with almost full strain recovery after 100% stretch. In a LiFePO₄/C-GPE/Li half-cell, the C-GPEs exhibit high electrochemical stability. Therefore, we consider that the prepared C-GPEs might have a potential application in flexible or/and stretchable energy storage devices

Reactive Compatibilization: Formation of Double-Grafted Copolymers by In Situ Binary Grafting and Their Compatibilization Effect

Reactive compatibilizers are usually used to enhance the compatibility of immiscible polymer blends. However, reactive linear compatibilizers containing reactive groups on the main chains form graft copolymers during reactive blending, and such graft copolymers with an asymmetric molecular structure are often “pulled in” or “pulled out” under mechanical shear. Double-grafted compatibilizers have a symmetric structure, and they usually exhibit higher compatibilizing efficiency. In this work, we propose a binary grafting strategy during melt blending to form compatibilizers located at the interface of an immiscible polymer blend. Specifically, poly­(methyl methacrylate) (PMMA) oligomer with carboxylic end groups (PMMA–COOH) and poly­(styrene-<i>co</i>-glycidyl methacrylate) (SG) copolymer were simultaneously incorporated into immiscible poly­(vinylidene fluoride)/poly­(l-lactic acid) (PVDF/PLLA) blends. The carboxylic acid groups of both the PMMA oligomer and PLLA can react with the epoxide groups on the SG main chains. Therefore, novel compatibilizing polymers with both PMMA and PLLA chains grafted onto the SG main chains form in situ. The grafted PMMA chains can entangle with PVDF, and the grafted PLLA chains are embedded in the PLLA phase, so the double-grafted copolymers act as effective compatibilizers for the PVDF/PLLA blends. Moreover, the effects of the PMMA molecular weight and PMMA loading (number of grafted PMMA side chains) on the compatibilization efficiency were investigated. The compatibilizing efficiency increases with increasing molecular weight and number of side chains in the ranges considered in this study. This one-pot synthesis of double-grafted compatibilizers by in situ grafting provides a new and simple method to prepare double-comb compatibilizers, and it offers the possibility of high-efficiency compatibilization

Compatibilization of Immiscible Polymer Blends Using <i>in Situ</i> Formed Janus Nanomicelles by Reactive Blending

Block or graft copolymers located at polymer–polymer interfaces have been considered as ideal compatibilizers for immiscible polymer blends. Herein, we report a novel compatibilization mechanism using Janus nanomicelles (JNMs) formed <i>in situ</i> at the polymer–polymer interface in immiscible polyvinylidene fluoride (PVDF)/polylactic acid (PLLA) blends. A small amount of a reactive graft copolymer, poly­(styrene<i>-<i>co</i>-</i>glycidyl methacrylate)<i>-<i>graft</i>-</i>poly­(methyl methacrylate) (P­((S<i>-<i>co</i>-</i>GMA)<i>-<i>g</i>-</i>MMA)), is incorporated into the PLLA/PVDF blends by simple melt mixing. The <i>in situ</i> grafting of PLLA chains onto P­((S<i>-<i>co</i>-</i>GMA)<i>-<i>g</i>-</i>MMA) during melt mixing leads to the formation of numerous JNMs with a shell structure consisting of PLLA and PMMA hemispheres. These JNMs are located at the PLLA/PVDF interface, where they behave as effective compatibilizers for the immiscible PLLA/PVDF blends. This interfacial micelle compatibilization (IMC) mechanism opens new opportunities to exploit interfacial emulsification using JNMs and should be of great significance in the compatibilization of polymer alloys

Effect of a Room-Temperature Ionic Liquid on the Structure and Properties of Electrospun Poly(vinylidene fluoride) Nanofibers

Novel anti-static nanofibers based on blends of poly­(vinylidene fluoride) (PVDF) and a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]­[PF₆], were fabricated using an electrospinning approach. The effects of the RTIL on the morphology, crystal structure, and physical properties of the PVDF nanofibers were investigated. Incorporation of RTIL leads to an increase in the mean fiber diameter and the rough fiber surface of the PVDF/RTIL composite nanofibers compared with the neat PVDF nanofibers. The PVDF in the PVDF/RTIL nanofibers exhibits an extremely high content (almost 100%) of β crystals, in contrast to the dominance of PVDF γ crystals in bulk melt-blended PVDF/RTIL blends. Nonwoven fabrics produced from the electrospun PVDF/RTIL composite nanofibers show better stretchability and higher electrical conductivity than those made from neat PVDF without RTIL, and are thus excellent antielectrostatic fibrous materials. In addition, RTIL greatly improved the hydrophobicity of the PVDF fibers, enabling them to effectively separate a mixture of tetrachloromethane (CCl₄) and water. The extremely high β content, excellent antielectrostatic properties, better stretchability, and hydrophobicity of the present PVDF/RTIL nanofibers make them a promising candidate for micro- and nanoscale electronic device applications

Nanostructured Poly(vinylidene fluoride)/Ionic Liquid Composites: Formation of Organic Conductive Nanodomains in Polymer Matrix

Nanostructured polymeric composites, based on a homopolymer poly­(vinylidene fluoride) (PVDF) and a small molecule, 1-vinyl-3-butylimidazolium chloride [VBIM]­[Cl], an unsaturated room-temperature ionic liquid (IL) have been fabricated. Our strategy forms organic conductive nanodomains with diameters of 20–30 nm dispersed homogeneously in the PVDF matrix. It is demonstrated that these conductive nanodomains are induced from microphase separation of the IL grafted PVDF (PVDF-<i>g</i>-IL) segments from the neat PVDF, which were produced by using electron-beam irradiation, leading IL molecules to graft onto the amorphous PVDF chains. It is also found that such microphase separation of PVDF-<i>g</i>-IL segments from PVDF matrix occurs only when the grafted IL content exceeds 3 wt %. Furthermore, the formed nanodomains enhance the crystallization rate of the matrix PVDF. The obtained nanostructured PVDF composites show dominant nonpolar α-phase of PVDF crystals and increased crystal long period (<i>L</i>) compared with neat PVDF. Additionally, the resulting nanostructured PVDF composites exhibit enhanced electrical properties, better Young’s modulus and ductility, and improved dielectric performance compared with neat PVDF, making the composites promising for potential use in superthin dielectric capacitors. The intriguing synthesis route will open up new opportunities for fabricating nanostructured polymer composites

Enhanced Interfacial Adhesion by Reactive Carbon Nanotubes: New Route to High-Performance Immiscible Polymer Blend Nanocomposites with Simultaneously Enhanced Toughness, Tensile Strength, and Electrical Conductivity

Physically anchoring carbon nanotubes (CNTs) onto the interface of immiscible polymer blends has been extensively reported; however, enhancement of physical properties of the blends has seldom been achieved. Herein, we used CNTs with reactive epoxide groups and long poly­(methyl methacrylate) (PMMA) tails as a thermodynamic compatibilizer for immiscible poly vinylidene fluoride/poly l-lactide (PVDF/PLLA) blends. The CNTs acted as an efficient compatibilizer and bridged the two phases through physical entanglement and chemical reaction. The sea–island structure of the blend transformed into a bicontinuous structure for CNT contents greater than 3 wt %. The mechanical properties, including ductility and tensile strength, thermal properties, and electrical conductivities were all enhanced by the CNTs compatibilizer. This strategy thermodynamically compatibilized by reactive nanofillers paves the way for advanced blend nanocomposites

Glass-Fiber Networks as an Orbit for Ions: Fabrication of Excellent Antistatic PP/GF Composites with Extremely Low Organic Salt Loadings

Polypropylene (PP)/glass fiber (GF) composites showing excellent antistatic performance were prepared by a simple melt process blending PP with GF and a small amount of organic salts (OSs). Two types of OSs, tribuyl­(octyl)­phosphonium bis­(trifloromethanesulfonyl)­imide (TBOP-TFSI) and lithium bis­(trifloromethanesulfonyl)­imide (Li-TFSI), with equivalent anions were used as antistatic agents for the composites. It was found that the GF and OSs exhibited significant synergistic effects on the antistatic performance as well as the mechanical properties of the composites. On the one hand, the incorporation of GF significantly enhanced the electric conductivity of the composites at a constant OS loading. On the other hand, the two types of OSs improved the interfacial adhesion between the GF and the PP matrix, which led to an enhancement of the mechanical properties. This study showed that OSs had specific interactions with GFs and were absorbed exclusively on the GF surface. The GF network in the PP matrix provided perfect orbits for the movement of ions, inducing the excellent antistatic performance exhibited by the PP/GF composites at an OS loading of as low as 0.25 wt % when the GF formed a network in the PP matrix

Nanostructured Thermoplastic Vulcanizates by Selectively Cross-Linking a Thermoplastic Blend with Similar Chemical Structures

Ethylene vinyl acetate rubber (vinyl acetate (VA) content = 50 wt %) (EVM) and ethylene vinyl acetate copolymer (VA content < 50 wt %) (EVA) are polymers with a very similar chemical structure. In this study, a novel thermoplastic vulcanizate (TPV) based on EVM/EVA28 (VA content = 28 wt %) blend has been successfully fabricated by dynamic vulcanization due to the selective cross-linking of EVM. The morphologies and properties of the TPVs have been investigated. It was found that the cross-linked EVM phase and the thermoplastic EVA28 phase form a perfect cocontinuous structure with the rubber phase size of about 100 nm. The fabricated TPV exhibits not only excellent stretchability (>900% elongation at break), nice elasticity (only about 19% remnant strain at 100% stretching), and good flexibility but also superior oil resistance

Poly(vinylidene fluoride) Nanocomposites with Simultaneous Organic Nanodomains and Inorganic Nanoparticles

Nanostructured polymeric dielectric composites, based on poly­(vinylidene fluoride) (PVDF), conductive carbon black (CB), and an unsaturated ionic liquid (IL), 1-vinyl-3-ethyl­imidazolium tetrafluoro­borate ([VEIM]­[BF₄]), were fabricated by melt blending and electron beam irradiation (EBI) methods. Our strategy forms simultaneous double nanophases in the PVDF matrix, that is, homogeneously dispersed CB nanoparticles and organic PVDF-<i>g</i>-IL nanodomains. The organic nanodomains were produced by microphase separation of the PVDF-<i>g</i>-IL chains from the PVDF matrix at melt state in the electron beam (EB) irradiated PVDF/IL-CB nanocomposites. Furthermore, the CB nanoparticles were fully adhered with these nanodomains, and novel structures with nanodomains@CB nanoparticle were achieved. Such nanodomains@CB nanoparticle structures showed a synergetic nucleating effect on the PVDF crystallization and led to the formation of dominant nonpolar α phases in the nano-PVDF/IL-CB composites. Because of the nanodomains adhesion of the CB nanoparticles, the nano-PVDF/IL-CB composites displayed a drastic reduction in dc conductivity compared with that of PVDF/CB and PVDF/IL-CB composites, respectively. Importantly, the resultant nano-PVDF/IL-CB composites exhibited significantly decreased losses relative to that of PVDF/CB, PVDF/IL, and PVDF/IL-CB composites. The structures of nanodomains@CB nanoparticle can be well responsible for this improvement of dielectric performance due to the fact that nanodomains confined the ion movements of IL in electric field and that their adhesion to the CB nanoparticle surfaces largely hindered the direct CB–CB nanoparticle contacts, thus decreasing their leakage currents. Our strategy not only fabricates PVDF/CB dielectric materials with good CB dispersion, higher dielectric permittivity, lower conductivity, and lower loss but also paves a new strategy for fabricating nanocomposites with double nanophases in polymer matrix

Effects of Surface Structure and Morphology of Nanoclays on the Properties of Jatropha Curcas Oil-Based Waterborne Polyurethane/Clay Nanocomposites

Three kinds of nanoclays with different structure and morphology were modified by γ-amino­propyl­triethoxysilane (APTES) and then incorporated into Jatropha oil-based waterborne polyurethane (WPU) matrix via in situ polymerization. The effects of surface structure and morphology of nanoclay on the degree of silylation were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). The results showed that the montmorillonite (MT) with abundant hydroxyl group structure and platelet-like morphology had the highest degree of silylation, while the modified halloysite nanotubes (HT) had the lowest grafting ratio. The effects of different silylated clays on the properties of WPU/clay nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), TGA, dynamic thermomechanical analysis (DMA) and tensile testing machine. SEM images showed that all silylated clays had good compatibility with WPU and were uniformly dispersed into the polymer matrix. WPU/SMT exhibited the best thermal properties owing to its intercalated structure. Dynamic thermomechanical analysis (DMA), atomic force microscope (AFM), and water contact angle results demonstrated that the silylated nanoclays enhanced the degree of microphase separation, surface roughness, and hydrophobicity of WPU/clay nanocomposites