Crystalline Polymer Matrix Research Articles

Ionic Liquid and Polymer Coated Garnet Solid Electrolytes for High‐Energy Solid‐State Lithium Metal Batteries

Garnet solid‐state electrolytes are promising for lithium metal batteries in terms of safety and stability. However, their rigid and brittle nature under humid air increase the interfacial resistance at the electrode/electrolyte interfaces. Herein, the ionic liquid (IL) 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]TFSI) is employed to dissolve poly(ethylene oxide) (PEO) polymer microstructures that facilitate ion transport through an amorphous rather than a crystalline polymer matrix. The PEO‐IL coatings on Ga doped garnet (LLZO) solid‐state electrolyte can effectively suppress the formation of Li2CO3 passivation layers on the garnet surface. Electrochemical impedance spectroscopy results show that the interfacial resistance of PEO‐IL coated Ga‐LLZO is much lower than that of uncoated Ga‐LLZO. In addition, the surface of PEO‐IL@Ga‐LLZO is flatter and it has a better contact with the Li anode than uncoated Ga‐LLZO. A symmetric cell of Li/PEO‐IL coated solid electrolyte/Li exhibits flat voltage profiles with overpotentials of less than 15 mV and shows a stable lithium plating/stripping process. A solid‐state battery based on PEO‐IL@Ga‐LLZO solid electrolyte combined with lithium metal anode and LiFePO4 (LFP) cathode delivers a specific capacity of ≈120 mAh g−1 with a Coulombic efficiency greater than 96% at 10 mA g(LFP) −1.

Enabling high performance all-solid-state lithium metal batteries using solid polymer electrolytes plasticized with ionic liquid

Ionic conductivity needs to be improved significantly for solid polymer electrolytes to be considered competitive alternatives to organic liquid electrolytes for battery technology. The strategy employed here is to promote polymer microstructures that facilitate ion transport by developing an amorphous rather than crystalline polymer matrix. To this end the transport, thermal, and electrochemical properties of solid polymer electrolytes incorporating ionic liquid (ILSPEs) are investigated. ILSPEs are fabricated into homogenous films using a hot-pressing procedure and are composed of a blend of poly (ethylene oxide) (PEO), triethylsulfonium bis(trifluoromethylsulfonyl)imide ionic liquid (S2TFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) salt. The goal of this work is to establish composition-property relationships that enable the ambient temperature operation of ILSPEs in a lithium metal battery. Optimized ILSPE compositions are able to achieve a high total ionic conductivity and Li+ transference number, 0.96 mS/cm at 22 °C and 0.31 at 60 °C respectively, that meet commercial benchmarks. The ILSPEs also show resistance to oxidation, with passivation up to 4.5 V (vs. Li+), and long-term stability with lithium metal, which enable good rate performance during room temperature cycling with a lithium metal anode and lithium iron phosphate cathode. Initial tests with higher potential lithium cobalt oxide cathode demonstrate promising performance.

Does the Type of Polymer and Carbon Nanotube Structure Control the Electromagnetic Shielding in Melt-Mixed Polymer Nanocomposites?

A suitable polymer matrix and well dispersed conducting fillers forming an electrically conducting network are the prime requisites for modern age electromagnetic shield designing. An effective polymer-based shield material is designed that can attenuate 99.9% of incident electromagnetic (EM) radiation at a minimum thickness of <0.5 mm. This is accomplished by the choice of a suitable partially crystalline polymer matrix while comparing non-polar polypropylene (PP) with polar polyvinylidene fluoride (PVDF) and a best suited filler nanomaterial by comparing different types of carbon nanotubes such as; branched, single-walled and multi-walled carbon nanotubes, which were added in only 2 wt %. Different types of interactions (polar-polar and CH-π and donor-acceptor) make b-MWCNT more dispersible in the PVDF matrix, which together with high crystallinity resulted in the best electrical conductivity and electromagnetic shielding ability of this composite. This investigation additionally conceals the issues related to the thickness of the shield material just by stacking individual thin nanocomposite layers containing different carbon nanotube (CNT) types with 0.3 mm thickness in a simple manner and finally achieves 99.999% shielding efficiency at just 0.9 mm thickness when using a suitable order of the different PVDF based nanocomposites.

Improvement in the Efficiency of Alkylsilyl Functionalized Copolymer for Polymer Solar Cells: Face‐On Orientation Enhanced by Random Copolymerization

Herein, an alkylsilyl functionalized alternative (D‐A1) copolymer with high crystallization property as the polymer matrix and planar [1,2‐c:4,5‐c]dithiophene‐4,8‐dione (BDD) block as the second acceptor unit (A2) are selected to construct two D‐A1‐D‐A2 type random copolymers PBDT‐TZ‐BDD‐1/19 and PBDT‐TZ‐BDD‐1/9. It is found that incorporation of a small amount of BDD block into the alkylsilyl functionalized copolymer by random copolymerization can effectively manipulate the energy levels, light absorption, molecular packing and the photovoltaic properties when blended with ITIC (indacenodithieno[3,2‐b]thiophene (IT) as the central donor unit and 2‐ (3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (IC) as end groups). More importantly, random copolymerization provides a beneficial trade‐off that the slightly reduced periodic sequence promotes the compatibility with the acceptor, whereas introduction of planar BDD units allows a preferred face‐on orientation with enhanced π–π stacking of the random copolymer to facilitate the charge transfer. As a result, the random copolymer PBDT‐TZ‐BDD‐1/19 delivers a significantly higher power conversion efficiency (11.02%) than the alternative binary copolymer counterpart together with the remarkably improved short circuit current and fill factor. These results demonstrate that random polymerization of a small amount of planar units into the highly crystalline polymer matrix is a promising strategy to develop high‐performance polymer solar cells.

One-step Synthesis and Enhanced Thermoelectric Properties of Polymer-Quantum Dot Composite Films.

Conventional syntheses of polymer-inorganic composite thermoelectric materials suffer major problems such as inhomogeneity, large particle size, and oxidation that result in ineffective loading. Now a one-step synthesis can be used to fabricate high-quality small-sized anions codoped poly(3,4-ethylenedioxythiophene):dodecylbenzenesulfonate/Cl-tellurium (PEDOT:DBSA/Cl-Te) composite films using a series of novel TeIV -based oxidants. The synchronized production of PEDOT and Te results in thick and homogeneous films containing evenly distributed and well-protected Te quantum dots. Owing to the heavily doped crystalline polymer matrix as well as the <5 nm unoxidized Te quantum dot loading, at low Te concentrations as 2.1-5.8 wt %, the films exhibits high power factors of about 100 μW m-1 K-2 , which is 50 % higher compared to a pure PEDOT:DBSA film.

One‐step Synthesis and Enhanced Thermoelectric Properties of Polymer–Quantum Dot Composite Films

AbstractConventional syntheses of polymer–inorganic composite thermoelectric materials suffer major problems such as inhomogeneity, large particle size, and oxidation that result in ineffective loading. Now a one‐step synthesis can be used to fabricate high‐quality small‐sized anions codoped poly(3,4‐ethylenedioxythiophene):dodecylbenzenesulfonate/Cl‐tellurium (PEDOT:DBSA/Cl‐Te) composite films using a series of novel TeIV‐based oxidants. The synchronized production of PEDOT and Te results in thick and homogeneous films containing evenly distributed and well‐protected Te quantum dots. Owing to the heavily doped crystalline polymer matrix as well as the &lt;5 nm unoxidized Te quantum dot loading, at low Te concentrations as 2.1–5.8 wt %, the films exhibits high power factors of about 100 μW m−1 K−2, which is 50 % higher compared to a pure PEDOT:DBSA film.

Tilted Orientation of Photochromic Dyes with Guest-Host Effect of Liquid Crystalline Polymer Matrix for Electrical UV Sensing.

We propose a highly oriented photochromic dye film for an ultraviolet (UV)-sensing layer, where spirooxazine (SO) derivatives are aligned with the liquid crystalline UV-curable reactive mesogens (RM) using a guest-host effect. For effective electrical UV sensing with a simple metal-insulator-metal structure, our results show that the UV-induced switchable dipole moment amount of the SO derivatives is high; however, their tilting orientation should be controlled. Compared to the dielectric layer with the nearly planar SO dye orientation, the photochromic dielectric layer with the moderately tilted dye orientation shows more than seven times higher the UV-induced capacitance variation.

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

In this work liquid-crystalline polymer (LCP) nanocomposites reinforced with in-situ reduced graphene oxide are investigated. Graphene oxide (GO) was first synthesized by the Hummers method, and the kinetics of its thermal reduc- tion was assessed. GO layers were then homogeneously dispersed in a thermotropic liquid crystalline polymer matrix (Vec- tran ® ), and an in-situ thermal reduction of GO into reduced graphene oxide (rGO) was performed. Even at low rGO amount, the resulting nanocomposites exhibited an enhancement of both the mechanical properties and the thermal stabil- ity. Improvements of the creep stability and of the thermo-mechanical behavior were also observed upon nanofiller incor- poration. Furthermore, in-situ thermal reduction of the insulating GO into the more electrically conductive rGO led to an important surface resistivity decrease in the nanofilled samples.

SWCNT Induced Crystallization in an Amorphous All-Aromatic Poly(ether imide)

We have selected two amorphous all-aromatic poly(ether imide)s with similar chemical structures but with different backbone geometries as matrices for SWCNT-based nanocomposites. Up to 4.4 vol %, SWCNTs could be incorporated using an in situ polymerization method. Nanocomposites prepared from aBPDA-P3, a nonlinear matrix polymer with a Tg of 230 °C, remains amorphous, and the presence of the SWCNTs reduces the Tg by 11 °C. No effect on E′ or stress–strain behavior was observed. When ODPA-P3 was used as the matrix, the SWCNTs appear to be highly compatible with this more linear polymer host. The SWCNTs act as a nucleating agent at concentrations as low as 0.1 vol %. XRD and TEM measurements show that the SWCNTs become embedded in a highly crystalline polymer matrix. The result is a significant change in thermomechanical properties. The polymer Tg was increased by 12 °C, from 196 to 208 °C, and due to the induced crystallinity, the modulus above Tg showed a dramatic increase. The neat polymer fails at Tg, b...

Hard nanocomposite comprising stereoregular syndiotactic polypropylene with chemically bonded gold nanoparticles

AbstractAn effective method to synthesize directly a hard composite material containing uniformly dispersed nanogold particles chemically bonded with a stereospecific, crystalline polymer matrix has been developed. Syndiotactic polypropylene was synthesized and functionalized to have a hydroxyl terminal group (sPPOH) via a metallocene catalysis with a selective chain transfer. Next, sPPOH was activated to react with ethylene sulfide forming the thiol‐terminated polymer, sPPSH. sPPSH was then chemically bonded to gold nanoparticles (AuNPs) formed in situ via a reduction of HAuCl4. The bonding between thiol and AuNP stabilized the AuNPs and led to the formation of sPPAuNPs composite containing uniformly‐dispersed AuNPs of a 19–40 nm size without noticeable aggregation. Furthermore, the chemical bonding of AuNPs has afforded sPPAuNPs a thermal degradation temperature (TD) 49.4 °C higher than the pristine sPP or sPPOH and 25.7 °C higher than sPPSH without any adverse effect on the crystalline temperature and melting temperature. In addition, the characteristic UV‐Vis absorption wavelength of sPPAuNPs remains the same at various temperatures, thus indicating the independence of optical property on temperature as well as the good thermal stability of the sPPAuNPs composite. 1H NMR, 13C NMR, FESEM, STEM, XPS, TGA and DSC were used to investigate the molecular structure, morphology and thermal properties of the resulting sPPAuNPs nanocomposite. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

In situ Localization of Molecules in Crosslinked Particles during Electrohydrodynamic Process: Simple Route to Produce Microcapsules and Fibers with Controlled Release

This study reports a spontaneous selective localization of molecules in crosslinked particles during electrospraying and electrospinning polymer solutions containing the particles. It provides a facile way of preparing microcapsules and fibers with controlled release. The dye molecules were phase separated from the crystalline polymer matrix during the electrohydrodynamic process and moved to the solvent-rich crosslinked particles. The position of the particles in the microcapsules and fibers could be controlled by adjusting compatibility of the particles with the matrix polymer. The microcapsules and fibers did not show the initial burst release of the molecules and gave considerably prolonged release behavior.

Compressibility and thermal expansion coefficients of nanocomposites with amorphous and crystalline polymer matrix

Clay-containing polymeric nanocomposites (CPNC) with polystyrene (PS) or polyamide-6 (PA-6) matrix were studied within T = 300–600 K and P = 0.1–190 MPa. From the Pressure–Volume–Temperature ( PVT) data the derivatives: compressibility, κ, and thermal expansion coefficient, α, were computed as functions of T, P and clay content, w. Dependence of these coefficients on P and T were significantly different for the amorphous PS than for the semi-crystalline PA-6. In the PS plots of κ and α vs. T the presence of secondary transitions, T β/ T g ≈ 0.9 ± 0.1 and T c/ T g = 1.2 ± 0.1, were detected and the clay effect at low T was prominent, affecting the physical aging. The isobaric values of α = α( T) were characterized by nearly T-independent values in the glassy and molten phase, connected by a large transitory region stretching from the ambient pressure values of T g to T c; this region was even more prominent in κ = κ( T). The derivative properties of PA-6 based CPNC were distinctly different. Here, the isobaric κ = κ( T) followed the same dependence on both sides of the melting zone, while the isobaric α = α( T) dependencies were dramatically different for the solid and molten phase; at T < T m α linearly increased with T, after melting its value sharply decreased, and then at T > T m (depending on w and P) either increased or decreased with T. Interpretation of the behavior in the melt and glass is based on the Simha–Somcynsky (S–S) cell-hole theory while that of the semicrystalline state on the Midha–Nanda–Simha–Jain (MNSJ) cell theory. In spite of the nonequilibrium conditions below the main transition point, T g or T m, the theories well predict the observed dependencies.

Phase and orientational ordering of low molecular weight rod molecules in a quenched liquid crystalline polymer matrix with mobile side chains.

We study the phase diagram and orientational ordering of guest liquid crystalline (LC) rods immersed in a quenched host made of a liquid crystalline polymer (LCP) matrix with mobile side chains. The LCP matrix lies below the glass transition of the polymer backbone. The side chains are mobile and can align to the guest rod molecules in a plane normal to the local LCP chain contour. A field theoretic formulation for this system is proposed and the effects of the LCP matrix on LC ordering are determined numerically. We obtain simple analytical equations for the nematic/isotropic phase diagram boundaries. Our calculation show a nematic-nematic (N/N) first order transition from a guest stabilized to a guest-host stabilized region and the possibility of a reentrant transition from a guest stabilized nematic region to a host only stabilized regime separated by an isotropic phase. A detailed study of thermodynamic variables and interactions on orientational ordering and phases is carried out and the relevance of our predictions to experiments and computer simulations is presented.

Predicting adhesion between a crystalline polymer and silane-treated glass surfaces in filled composites

Results reported earlier showing a close correlation between measured adhesion strength of bonds between silane-modified glass and various amorphous thermoplastics and a thermodynamic compatibility criterion based on UNIFAC are extended to the case of a crystalline polymer matrix. The criterion used is the magnitude of the (negative) molar Gibbs free energy of mixing, (-ΔGmix)0.5, for a pseudo-solution consisting of equal molar amounts of the repeat units of the polymer matrix and the organo-functional group of the silane coupling agent, but the measurements leading to the values of the adhesion strength are carried out using a three-point bending test, in which a rectangular polymer specimen filled to a high volume fraction with silane-treated glass beads is subjected to increasing load until the composite breaks or yields. Earlier work showed a good correlation between the adhesion energy computed from single-partcle composite measurements and the value of (-ΔGmix)0.5 computed using UNIFAC for a variety of organo-silane-modified spheres imbedded in three different amorphous polymeric matrices. The present work extends the database to a crystalline matrix, viz. poly(ethylene terephthalate), and uses a nonoptical adhesion test to obtain flexural yield strengths. The values of the latter are also found to be in good agreement with the predictive thermodynamic criterion.

The effect of interfacial microstructure on the interfacial strength of glass fiber/polypropylene resin composites

AbstractIn this study, a new method to form resin droplets on fibers has been developed, and samples for the single fiber pull‐out test were prepared using this method. The effects of microstructure of polypropylene (PP) resin and the microstructure of interface between the glass fiber and PP resin on the interfacial strength have been investigated. In addition, the influence of the microstructure of the interface on the interfacial strength of glass fiberreinforced PP composites have been discussed. It has been found that in the pull‐out test, the transcrystallinity formed at the interface between the glass fiber and PP resin improved the interfacial strength when no spherulites developed in the PP matrix. On the other hand, it has been found that when the spherulites were well developed in the PP matrix, the transcrystallinity formed at the interface reduced the interfacial strength. Finally, rapid cooling has been shown to improve the interfacial strength between the fiber and resin in the crystalline polymer matrix composites. © 1994 John Wiley &amp; Sons, Inc.

Small Angle X-Ray Scattering on Poly(Ethylene-Methacrylic Acid) Lead and Lead Sulfide Ionomers

ABSTRACTThe morphology of ionomers, e.g., poly(ethylene-methacrylic acid) (EMA) lead salts (EMA/Pb) and lead sulfide compounds (EMA/PbS), has been studied by using the techniques of small angle x-ray scattering (SAXS), anomalous SAXS (ASAXS), wide angle x-ray scattering (WAXS), and differential scanning calorimetry (DSC). EMA/Pb containing less than 5 wt% of lead exhibited two characteristic SAXS peaks which corresponded to the lamellar structure of the partially crystalline polymer matrix and the ionic structure of the lead aggregates that were present in the amorphous regions. The lead aggregates were not distributed uniformly and increased in packing density with increasing lead content. Both DSC and WAXS showed that the crystalline phase was present for all EMA/Pb samples and that the crystallinity decreased slightly with increasing lead content. ASAXS near the L3 absorption edge of lead permitted the extraction of the scattered intensity of lead ions from the SAXS patterns of the superimposed crystalline and ionic structures. Correlation function analysis revealed that the ionic aggregates of the EMA/Pb containing 5 wt% of lead could be described by a liquid-like model with a short range order of 2-4 nm. EMA/PbS samples were made by a reaction of EMA/Pb ionomers with hydrogen sulfide. Instead of an ionic peak as shown by EMA/Pb samples, the SAXS patterns of EMA/PbS showed a broad diffraction peak located at the same q value as the lamellar peak of the EMA in acid form. The (lamellar) peak could be attributed to the interference between the PbS crystallites in the neighboring lamellae.