Comb Copolymers Research Articles

A highly efficient nanofibrous air filter membrane fabricated using electrospun amphiphilic PVDF-g-POEM double comb copolymer.

Current global emergencies, such as the COVID-19 pandemic and particulate matter (PM) pollution, require urgent protective measures. Nanofibrous air filter membranes that can capture PM0.3 and simultaneously help in preventing the spread of COVID-19 are essential. Therefore, a highly efficient nanofibrous air filter membrane based on amphiphilic poly(vinylidene fluoride)-graft-poly(oxyethylene methacrylate) (PVDF-g-POEM) double comb copolymer was fabricated using atomic transfer radical polymerization (ATRP) and electrospinning. Fourier transform infrared spectroscopy, X-ray diffraction, proton nuclear magnetic resonance, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis were employed to successfully characterize the molecular structure of the fabricated amphiphilic PVDF-g-POEM double comb copolymer. The nanofibrous air filter membrane based on amphiphilic PVDF-g-POEM double comb copolymer achieved a low air resistance of 4.69mm H2O and a high filtration efficiency of 93.56 % due to enhanced chemical and physical adsorption properties.

Designing double comb copolymer as highly lithium ionic conductive solid-state electrolyte membranes

We present highly mechanical strength and ionic conductive solid-state electrolyte membranes based on amphiphilic double comb copolymer, i.e., poly(vinylidene chloride)-graft-poly(methyl methacrylate) (PVDC-g-PMMA) synthesized through atomic transfer radical polymerization (ATRP). Well-defined nanophase-separated amphiphilic double comb copolymers are complexed with two types of Li salts (LiTFSI and LiClO4) to form a solid-state electrolyte membrane. Compared to other types, the highest ionic conductivity of the solid-state electrolyte membranes is observed in an amphiphilic double comb copolymer with PVDC-g-PMMA/LiTFSI, due to the synergy of the dissociability of TFSI− and the hopping transport of lithium ions facilitated by PMMA chains. Moreover, the lowest activation energy (0.15 eV) and excellent ionic conductivity (1.3 × 10−3 S cm−1) are also observed in the same solid-state electrolyte membranes at room temperature.

Experimental method and thermodynamic model for competitive adsorption between polycarboxylate comb copolymers

This study presents a method that establishes the existence of competitive adsorption between polycarboxylate ether (PCE) molecules with different molecular architecture. By combining well-established total organic carbon measurements with UV–Visible absorption, competition between PCEs of different structures could be quantified.Results are interpreted by deriving a fundamental thermodynamic model describing the PCE competition as a dynamic equilibrium between adsorbed and dissolved PCE molecules with different architectures. The model rationalizes the effect of dispersity in charge and backbone length on the adsorption behavior of PCEs and contributes to a fundamental understanding of the PCE working mechanism on the molecular level.

In-situ formation of asymmetric thin-film, mixed-matrix membranes with ZIF-8 in dual-functional imidazole-based comb copolymer for high-performance CO2 capture

Despite numerous studies on free-standing, mixed-matrix membranes (MMMs), the development of thin-film MMMs with high permeance is still an ongoing challenge. Here, the successful fabrication of ultra-high-permeance thin-film MMMs on a porous polymer substrate is described based on a highly porous zeolitic imidazole framework (ZIF-8) and a dual-functional imidazole-based comb copolymer. The copolymer of poly(vinyl imidazole)-poly(oxyethylene methacrylate) (PVI-POEM) is synthesized via free-radical polymerization, and it exhibits CO2-philicity, strong adhesion, and good interactions with fillers. In contrast to commercial benchmark membranes such as Pebax, the use of the PVI-POEM comb copolymer results in significant improvement in the CO2 permeance without significant loss of selectivity even at high ZIF-8 loadings and low thickness. It is attributed to the in-situ formation of inverse, asymmetric morphology of MMMs and partial infiltration of PVI-POEM chains into ZIF-8 particles. Optimization of the preparation process, such as ZIF-8 loading, substrate type, and coating layer thickness, leads to an extremely high CO2 permeance of 4474 GPU with high CO2/N2 and CO2/CH4 ideal selectivities of 32.0 and 12.4, respectively, which is far beyond the current trade-off limit for membranes. The mechanism behind the exceptionally high CO2 separation performance is delineated by exploring molecular dynamic simulation through morphology, structural, and energetic analyses.

Adhesive, free-standing, partially fluorinated comb copolymer electrolyte films for solid flexible supercapacitors

Solid-state electrolytes exhibiting high safety and flexibility have attracted global attention as an alternative to conventional fluidic and flammable liquid electrolytes for energy storage devices. Herein, we report a free-standing solid electrolyte film with high ionic conductivity, strong adhesive property, and good mechanical strength based on a partially fluorinated, microphase-separated comb copolymer consisting of superhydrophobic poly(2,2,2-trifluoroethyl methacrylate) and amphiphilic crystalline poly(ethylene glycol) behenyl ether methacrylate. The comb copolymer electrolyte film with ionic liquid (IL) exhibited a wide potential window of 2.2 V and retained its excellent flexibility up to 85 wt% IL loading. This property arises from the self-assembled microphase separation, which functions as an effective channel for ion transportation, resulting in improved ionic conductivity. The electrolyte film was applied to a solid supercapacitor with activated carbon electrodes, resulting in a high specific capacitance (37.3 F g−1), energy density (23.2 Wh kg−1), and power density (530 W kg−1), and outperformed the cells made with conventional poly(vinyl alcohol) electrolyte. Interestingly, the fabrication of supercapacitors did not require any separator, adhesive, or packaging process because of the strong self-adhesive and mechanical properties of the comb copolymer electrolyte film.

Tailored ZnO Nanostructure Based Quasi-Solid-State Electrolyte and Mesoporous Carbon Electrocatalyst for Solar Energy Conversion

We have investigated the photoelectrochemical influence of quasi-solid-state electrolytes based on tailored ZnO nanostructures and mesoporous carbon electrocatalyst in the solar conversion performance of dye-sensitized solar cells (DSSCs). Tailored ZnO nanostructures with rod-shaped petals (ZnO nanorod) and almond-shaped petals (ZnO nanoalmond), were prepared using the hydrothermal method, respectively. Mesoporous carbon electrocatalyst with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The phase and structure of tailored ZnO nanostructures were investigated using scanning electron microscopy (SEM) and wide angle X-ray scattering (WAXS). Diffuse reflectance, intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS), electrochemical impedance spectroscopy (EIS) measurements were used to investigate the optical and electrochemical properties of quasi-solid-state electrolytes. The quasi-solid-state electrolytes based on ZnO nanorod significantly improved the solar conversion performance owing to its enhanced scattering effect, ion diffusion, effective path for redox couple transfer, and sufficient penetration of quasi-solid-state electrolytes into the electrode. The quasi-solid-state electrolytes based on ZnO nanorod, ZnO nanoalmond and mesoporous carbon electrocatalyst showed a solar conversion efficiency of 6.4%, 5.4%, respectively, which is higher than that of the polymer gel electrolytes (4.7%).

Working Mechanisms and Design Principles of Comb-like Polycarboxylate Ether Superplasticizers in Cement Hydration: Quantitative Insights for a Series of Well-Defined Copolymers

Cement and concrete are the most widely used building materials and contain comb copolymers such as polycarboxylate ethers (PCEs) as hydration and setting modifiers. The working mechanisms of these additives in cement hydration have remained uncertain, which limits the rational design of additives and of new cement materials with lower CO2 footprint. We identified quantitative correlations between PCE copolymer structure, adsorption, and cement setting properties for a series of copolymer structures and concentrations, combined with insights into conformations and adsorption mechanisms by atomistic simulations. The PCE copolymers have only a small fraction of polydispersity compared to earlier studies, and molecular dynamics simulations utilize Interface force field models for C-S-H phases that enable order-of-magnitude more accurate insights into the dynamics of the nanoscale polymer interfaces compared to earlier models. Two distinct sets of property correlations were discovered. (1) The carboxylate content of the PCEs, i.e., the molar density of ionic side groups per unit mass, correlates with the adsorbed amount of polycarboxylate ethers onto cement pastes, the conductivity of the cement paste, and the retardation of the acceleration period of cement hydration. (2) The combination of the ionic character of the polymer backbone and the length of non-ionic polyethylene glycol (PEG) side chains correlates with the water-to-cement ratio necessary for processing, zeta potentials, and fluidity of the cement pastes in mini slump tests. Simulations indicate that PCE adsorption onto cement particles involves migration of calcium ions in the acrylate backbone onto the calcium silicate hydrate surface, or calcium hydroxide surfaces, followed by ion pairing of the anionic polymer backbone with the positively charged mineral surface. PEG side chains exhibit no affinity to the mineral surface. The best fluidity and water reduction are achieved using an optimum ratio of the volume of PEG side chains to the volume of the anionic backbone, balancing sufficient surface bonding through the ionic backbone and minimization of interparticle forces by the non-ionic PEG side chains. A charge density too low prevents effective adsorption, and a charge density too high leads to multilayer deposition and ionic agglomeration forces between coated particles that reduce the fluidity and increase the necessary water-to-cement ratio. The proposed mechanism supersedes prior models and provides quantitative metrics for the rational design of polymer additives for cement and related particle dispersions.

Preparation of Co9S8 nanostructure with double comb copolymer derived mesoporous carbon for solar energy conversion catalyst

This work reports the development of a facile hybrid based on Co9S8 nanostructure embedded on sheets of mesoporous carbon (meso C) from double comb copolymer, which can serve as excellent counterelectrode for ssDSSCs showing great promise to replace Pt. Co9S8 with high catalytic active nature is synthesized via the hydrothermal method. Meso C with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The structural and morphological characterization of the Co9S8 /meso C revealed well defined crystalline nanostructure of Co9S8 uniformly embedded on the surfaces of the meso C. The photoelectrochemical characterization suggests that the use of the Co9S8/meso C nanostructure enhances the efficiency of the reduction of I3− to 3I− at the counterelectrode/solid state electrolyte interface. The ssDSSCs assembled with the Co9S8 /meso C showed an enhanced solar energy conversion efficiency comparable to a conventional Pt. The enhanced solar energy conversion efficiency of Co9S8/meso C could be attributed to the high catalytic active nature and improved electrochemical surface area. In addition, because of the robust structure of Co9S8/meso C counterelctrode based on ssDSSCs maintains 90% efficiency at least for 10 day.

PH responsive switchable protein adsorption properties of poly(2-methyl-2-oxazoline)/ poly(4-vinyl pyridine) based coatings: Influence of poly(4-vinyl pyridine) chain length and ionic strength

Protein adsorption at interfaces is a key for many applications especially in the biomedical field, biotechnologies, biocatalysis, food industry, etc. The development of surface layers that allow to control and manipulate protein adsorption is thus highly desired. To achieve this desired goal, we designed a smart thin stimuli responsive coating based on poly[(2-methyl-2-oxazoline)-random-glycidyl methacrylate)] (PMOXA-r-GMA) comb copolymer and poly(4-vinyl pyridine)-block-poly(glycidyl methacrylate) (P4VP-b-PGMA) block copolymer and scrutinized its ability to control protein adsorption properties by unraveling the effect of ionic strength (I) along with the pH of the surrounding medium and variation of chain length of P4VP. Firstly, PMOXA/P4VP based coatings were prepared by spin coating the mixture of PMOXA-r-GMA and P4VP-b-PGMA copolymer solutions onto silicon substrates followed by annealing at 110 °C. The surface composition and morphology of the PMOXA/P4VP based coatings were evaluated through X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The switchable ability of the coating with the variation of chain length of P4VP upon pH and ionic strength trigger was characterized by water contact angle (WCA) and variable angle spectroscopic ellipsometry (VASE). The experimental observations illustrated that the change in the water contact angle (ΔWCA) and thickness (Δh) were found to be maximum when the chain length of P4VP was almost three times that of PMOXA while turning the environmental condition from pH 3, with low ionic strength (I = 10−3 M) to pH 9 with high ionic strength (I = 10-1 M). Finally, the adsorption and desorption behavior of mixed polymer coating against bovine serum albumin (BSA) protein was analyzed qualitatively and quantitatively using the fluorescein isothiocyanate-labelled BSA (FITC-BSA) assay and quartz crystal microbalance with dissipation monitoring (QCM-D), respectively. The low ionic strength (I = 10-3 M) at pH 3, caused to increase the adsorption of BSA and this increment was enhanced by increasing the chain length of P4VP in PMOX/P4VP based coatings. Subsequently, the adsorbed protein was then efficiently desorbed by changing the conditions to pH 9, I = 10-1 M, as well as the maximum desorption percentage (> 92 %) could be obtained at these optimized conditions in PMOXA/P4VP based polymer coatings.

Shape-Controlled TiO2 Nanomaterials-Based Hybrid Solid-State Electrolytes for Solar Energy Conversion with a Mesoporous Carbon Electrocatalyst.

One-dimensional (1D) titanium dioxide (TiO2) is prepared by hydrothermal method and incorporated as nanofiller into a hybrid polymer matrix of polyethylene glycol (PEG) and employed as a solid-electrolyte in dye-sensitized solar cells (DSSCs). Mesoporous carbon electrocatalyst with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The 1D TiO2 nanofiller is found to increase the photoelectrochemical performance. As a result, for the mesoporous carbon-based DSSCs, 1D TiO2 hybrid solid-state electrolyte yielded the highest efficiencies, with 6.1% under 1 sun illumination, in comparison with the efficiencies of 3.9% for quasi solid-state electrolyte and 4.8% for commercial TiO2 hybrid solid-state electrolyte, respectively. The excellent photovoltaic performance is attributed to the improved ion diffusion, scattering effect, effective path for redox couple transfer, and sufficient penetration of 1D TiO2 hybrid solid-state electrolyte into the electrode, which results in improved light-harvesting, enhanced electron transport, decreased charge recombination, and decreased resistance at the electrode/electrolyte interface.

Compatibilization of Poly(Lactic Acid) (PLA)/Plasticized Cellulose Acetate Extruded Blends through the Addition of Reactively Extruded Comb Copolymers.

In the perspective of producing a rigid renewable and environmentally friendly rigid packaging material, two comb-like copolymers of cellulose acetate (AC) and oligo(lactic acid) OLA, feeding different percentages of oligo(lactic acid) segments, were prepared by chemical synthesis in solvent or reactive extrusion in the melt, using a diepoxide as the coupling agent and were used as compatibilizers for poly(lactic acid)/plasticized cellulose acetate PLA/pAC blends. The blends were extruded at 230 °C or 197 °C and a similar compatibilizing behavior was observed for the different compatibilizers. The compatibilizer C1 containing 80 wt% of AC and 14 wt% of OLA resulted effective in compatibilization and it was easily obtained by reactive extrusion. Considering these results, different PLAX/pAC(100-X) compounds containing C1 as the compatibilizer were prepared by extrusion at 197 °C and tested in terms of their tensile and impact properties. Reference materials were the uncompatibilized corresponding blend (PLAX/pAC(100-X)) and the blend of PLA, at the same wt%, with C1. Significant increase in Young’s modulus and tensile strength were observed in the compatibilized blends, in dependence of their morphologic features, suggesting the achievement of an improved interfacial adhesion thanks to the occurred compatibilization.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Self-assembled lamellar nanochannels in polyoxometalate-polymer nanocomposites for proton conduction

The construction of nanostructured ion-transport channels is highly desirable in the design of advanced electrolyte materials, as it can enhance ion conductivity by offering short ion-transport pathways. In this work, we present a supramolecular strategy to fabricate a nanocomposite electrolyte containing highly ordered lamellar proton-conducting nanochannels, by the electrostatic self-assembly of a polyoxometalate H3PW12O40 (PW) and a comb copolymer poly(4-methlstyrene)-graft-poly(N-vinyl pyrrolidone). PW can effectively regulate the self-assembling order of polymer moieties to form a large-range lamellar structure, meanwhile, introducing protons into the nanoscale lamellar domains to build proton transport channels. Moreover, the rigid PW clusters contribute a remarkable mechanical reinforcement to the nanocomposites. The lamellar nanocomposite exhibits a conductivity of 4.3 × 10−4 S/cm and a storage modulus of 1.1 × 107 Pa at room temperature. This study provides a new strategy to construct nanostructured ion-conductive pathways in electrolyte materials.

Mille-feuille-like heterostructures through in situ cross-linking approach for high power density supercapacitor

Tailoring the heterostructure of transition metal compounds is considered a promising approach for developing high-performance electrode materials for energy storage devices. In this study, a mille-feuille-like cobalt oxide/sulfide (MF-S) on Ni foam comprising porous microspheres between interconnected nanosheet walls is successfully synthesized via a one-pot solvothermal process and sulfurization. The unique heterostructure is generated using in situ cross-linking during the solvothermal process, resulting from the reaction between the epoxy groups of the comb copolymer and amine group of diethylentrieamine (DETA). The comb copolymer consisting of poly(glycidyl methacrylate)–co-poly(oxyethylene methacrylate) (PGMA-POEM) is synthesized via free-radical polymerization and serves as the structure directing agents. The prepared MF-S electrode exhibits outstanding electrochemical performance with high specific capacitance (1138F g−1 or 142 mAh g−1 at 3 A g−1) and good cycle stability owing to the synergistic effect of well-ordered nanosheets and nanospheres. Moreover, the all-solid-state, bendable asymmetric supercapacitor fabricated with the MF-S and activated carbon electrodes achieves an exceptional power density of 35000 W kg−1 at a high energy density of 18.1 Wh kg−1 with excellent cycling stability (86.9%, 10,000 cycles).

Synthesis, Characterization, and CO2/N2 Separation Performance of POEM-g-PAcAm Comb Copolymer Membranes.

Alcohol-soluble comb copolymers were synthesized from rubbery poly(oxyethylene methacrylate) (POEM) and glassy polyacrylamide (PAcAm) via economical and facile free-radical polymerization. The synthesis of comb copolymers was confirmed by Fourier-transform infrared and proton nuclear magnetic resonance spectroscopic studies. The bicontinuous microphase-separated morphology and amorphous structure of comb copolymers were confirmed by wide-angle X-ray scattering, differential scanning calorimetry, and transmission electron microscopy. With increasing POEM content in the comb copolymer, both CO2 permeability and CO2/N2 selectivity gradually increased. A mechanically strong free-standing membrane was obtained at a POEM:PAcAm ratio of 70:30 wt%, in which the CO2 permeability and CO2/N2 selectivity reached 261.7 Barrer (1 Barrer = 10−10 cm3 (STP) cm cm−2 s−1 cmHg−1) and 44, respectively. These values are greater than those of commercially available Pebax and among the highest separation performances reported previously for alcohol-soluble, all-polymeric membranes without porous additives. The high performances were attributed to an effective CO2-philic pathway for the ethylene oxide group in the rubbery POEM segments and prevention of the N2 permeability by glassy PAcAm chains.

Substrate-independent three-dimensional polymer nanosheets induced by solution casting.

Nanosheets are important structures usually composed of inorganic materials, such as metals, metal oxides, and carbon. Their creation typically involves hydrothermal, electrochemical or microwave processes. In this study, we report a novel formation mechanism of 3D polymer nanosheets via facile solution casting using a comb copolymer consisting of poly(ethylene glycol) behenyl ether methacrylate and poly(oxyethylene) methacrylate (PEGBEM–POEM). Controlling the composition of comb copolymer yielded nanosheets with different packing density and surface coverage. Interestingly, the structure exhibits substrate independence as confirmed by glass, inorganic wafer, organic filter paper, and porous membrane. The formation of 3D nanosheets was investigated in detail using coarse-grained molecular dynamics simulations. The obtained polymer nanosheets were further utilized as templates for inorganic nanosheets, which exhibit high conductivity owing to interconnectivity, and hence have promising electronic and electrochemical applications.

Solid-state facilitated transport membrane for CO/N2 separation based on PHMEP-co-PAA comb-like copolymer: Experimental and molecular simulation study

Carbon monoxide (CO) is an important raw material in chemical industries; however, its separation through solid-state polymer membranes has not been extensively investigated. Herein, a series of comb-like copolymers, i.e., poly(2-hydroxypropyl-2-(methacryloyloxy) ethyl phthalate-co-acrylic acid) (PHMEP-co-PAA), is synthesized and used as a matrix to incorporate AgBF4 and ionic liquid ([bmim][BF4]) for solid-state facilitated CO transport membrane. The carbonyl moeities of the copolymer phthalate and carboxyl groups effectively form a complex with the Ag ions. CO/N2 separation performance is improved by introducing AgBF4 together with [bmim][BF4] into the copolymer matrix, which is supported by spectroscopic analysis and molecular dynamics simulations. Incorporating AgBF4 significantly increases the interaction energy between the membrane and CO molecules, demonstrating that Ag salts act as facilitated CO transport carriers and increase CO solubility in the membrane. Results show that the ionic liquid prevents comb copolymer aggregation and improves CO/N2 selectivity. The PHMEP-co-PAA copolymer monomeric ratio affects the CO/N2 selectivity and carrier stability. Copolymers with high PHMEP content (70 wt%) show the highest CO/N2 selectivity due to strong polymer-CO interaction energies. Performance optimization provided a CO/N2 selectivity of 16.2, one of the highest values reported so far, with a CO permeance of 2.1 GPU. Simultaneous increase in CO permeance and CO/N2 selectivity with carrier loading clearly indicates facilitated CO transport. The simulation analysis effectively interprets the experimental separation performance and can be used for designing CO separation membranes.

Amphiphilic micelle-forming PDMS-PEGBEM comb copolymer self-assembly to tailor the interlamellar nanospaces of defective poly(ethylene oxide) membranes

An amphiphilic comb copolymer was synthesized via free-radical polymerization using two macromonomers: monomethacryloxypropyl-terminated poly(dimethyl siloxane) (PDMS-MA, 10,000 g mol−1) and poly(ethylene glycol)–behenyl ether methacrylate (PEGBEM, 1500 g mol−1). The PDMS-PEGBEM comb copolymer underwent self-assembly to form micellar structures in ethanol/tetrahydrofuran solvent. The micelle-forming PDMS-PEGBEM copolymer was incorporated into the low-cost, commercially available polymer, and non-selective polymer poly(ethylene oxide) (PEO, 106 g mol−1), resulting in highly selective all-polymeric membranes. The alignment of the PDMS-PEGBEM micelles in the interlamellar region of PEO and the corresponding increase in the domain spacing were observed by transmission electron microscopy and small-angle X-ray scattering, confirming the successful encapsulation of PDMS-PEGBEM in the interlamellar region. The PDMS functions as a rubbery filler between the crystallites, whereas PEGBEM has good affinity towards PEO because of their chemical similarity. The CO2/N2 and CO2/CH4 selectivities of PEO membranes was significantly enhanced from 0.78 and 0.71 to 41.7 and 13.3, respectively, on the loading of 10 wt.% of the copolymer. The highest CO2 permeability reached 240 barrer at 50 wt.% copolymer loading, with the CO2/N2 and CO2/CH4 selectivities of 34.6 and 12.2, respectively. Herein, the evolution of the interlamellar nanospaces and dual-phase region, as well as the microstructures of the membranes are reported.

1D Co4S3 nanoneedle array with mesoporous carbon derived from double comb copolymer as an efficient solar conversion catalyst

This study investigates the use of a one-dimensional (1D) cobalt sulfide/mesoporous carbon heterogeneous electrocatalyst as counter electrode for high solar energy conversion efficiency in dye-sensitized solar cells (DSSCs). The 1D cobalt oxide (Co3O4) was in situ hydrothermally grown on the fluorine-doped tin oxide glass substrate, followed by sulfurization to form 1D cobalt sulfide (Co4S3) nanoneedle array. The Co4S3 is characterized by a high electrocatalytic activity for reducing/oxidizing the redox couple in the electrolyte. Additionally, the 1D structural feature of the Co4S3 allows fast electron transport through the oriented diffusion pathway. However, the Co4S3 still has relatively low chemical stability and poor electrical conductivity than conventional Pt catalyst. Herein, we incorporated the mesoporous carbon layer derived from the double comb copolymer, i.e., PVDC-g-POEM, which can act as a mesoporous structural template and sufficient carbon source. This strategy increased the electrocatalytic activity and chemical durability of the heterogeneous catalytic materials. The 1D Co4S3/mesoporous carbon heterogeneous catalyst exhibited excellent electrocatalytic activity for the reduction of triiodide, thereby outperforming the conventional Pt counter electrode. The catalytic properties were demonstrated by electrochemical analysis, i.e., cyclic voltammetry and electrochemical impedance spectroscopy. Results suggest that solid-state DSSCs (ssDSSCs) fabricated with the 1D Co4S3/mesoporous carbon counter electrode exhibited a higher solar energy conversion efficiency of 6.2% than the corresponding ssDSSC with conventional Pt (5.7%). The pure 1D Co4S3 or mesoporous carbon showed relatively lower performance than conventional Pt. Accordingly, the 1D Co4S3/mesoporous carbon synergetic approach represents a new strategy for enhancing the catalytic activity and chemical stability for highly efficient ssDSSCs.

Use of non-selective, high-molecular-weight poly(ethylene oxide) membrane for CO2 separation by incorporation of comb copolymer

Although ethylene oxide units are often incorporated into polymeric membranes for CO2 separations, high-molecular-weight poly(ethylene oxide) (high-Mw PEO) cannot be used effectively due to its inferior separation performance, despite its good solubility in mild solvents (e.g. water and alcohols) and commercial availability at low cost. A high-performance, defect-free membrane for CO2 separations based on high-Mw PEO was prepared by incorporating the crosslinkable poly(glycidyl methacrylate-g-polypropylene glycol)-co-poly(oxyethylene methacrylate) (PGP-POEM) comb copolymer. The CO2/N2 and CO2/CH4 selectivity of the neat high-Mw PEO membrane was as low as 0.8 and 0.6, respectively, which increased drastically with increasing comb copolymer content, and the thermal and mechanical properties were also improved. The three-dimensionally interweaved network of the comb copolymer occurred within the PEO matrix, which had a considerable effect on the crystalline structure of the membranes. The crystalline morphology of the membranes and the distribution of comb copolymer within the PEO matrix were comprehensively examined according to the comb copolymer content. The comb copolymer effectively suppressed the formation of non-selective defects by filling the interlamellar and interfibrillar regions of the PEO crystallites. The best separation performance was achieved with a comb copolymer loading of 30 wt%, showing a CO2 permeability of 120.9 barrer with CO2/N2 and CO2/CH4 selectivity of 44.9 and 14.5, respectively. The tensile strength and elongation at break reached 7.5 MPa and 1490%, respectively. This work presents an avenue for utilizing a low-cost, commercially-available, high-Mw PEO in gas separation applications, providing insight into the crystalline structure and morphology of these membranes.