Polyfluorene-poly(ethylene oxide) diblock copolymers: synthesis and electron transport behavior.

Under mild reaction conditions, we synthesized diblock copolymers of poly(9,9-dioctylfluorene)-block-poly(ethylene oxide) (PFO-b-PEO) via end-capping poly(9,9-dioctylfluorene) (PFO) with poly(ethylene oxide) (PEO) on one end. We investigated the thermal, optical, electrochemical and crystalline properties as well as electron transport performance of these polymers. Our results demonstrate that PFO-b-PEO diblock copolymers with short PEO chains (M n = 1000 and 2000 g mol-1) exhibit higher electron mobilities compared to the PFO homopolymer and longer PEO chain (M n = 4000 g mol-1) attached copolymers. This enhanced electron mobility is attributed to the higher crystallinity induced by the shorter PEO chain end-capping.

Synthesis and Electron Transporting Properties of Diblock Copolymers Consisting of Polyfluorene and Polystyrene.

Poly(9,9-di-n-octylfluorene) (PFO) is a promising material for polymer light-emitting diodes (PLEDs) due to its advantageous properties. To enhance its electron transporting capabilities, diblock polymers were synthesized by attaching polystyrene (PSt) chains of varying lengths to one end of the PFO molecule. In a comparative study with PFO homopolymer, the diblock polymers maintained similar thermal properties, absorption spectra, and photoluminescent stability, while exhibiting slightly deeper lowest unoccupied molecular orbital (LUMO) levels and higher crystallinity. Notably, diblock polymers with shorter polystyrene blocks demonstrated higher electron mobility than the PFO homopolymer and diblock polymers with excessively long polystyrene blocks. These findings suggest that the optimal chain length of the polystyrene block is crucial for maximizing electron mobility, thus offering valuable insights for designing high-performance PLED materials.

The opportunity of membrane technology for hydrogen purification in the power to hydrogen (P2H) roadmap: a review.

The global energy market is in a transition towards low carbon fuel systems to ensure the sustainable development of our society and economy. This can be achieved by converting the surplus renewable energy into hydrogen gas. The injection of hydrogen (⩽10% v/v) in the existing natural gas pipelines is demonstrated to have negligible effects on the pipelines and is a promising solution for hydrogen transportation and storage if the end-user purification technologies for hydrogen recovery from hydrogen enriched natural gas (HENG) are in place. In this review, promising membrane technologies for hydrogen separation is revisited and presented. Dense metallic membranes are highlighted with the ability of producing 99.9999999% (v/v) purity hydrogen product. However, high operating temperature (⩾300 °C) incurs high energy penalty, thus, limits its application to hydrogen purification in the power to hydrogen roadmap. Polymeric membranes are a promising candidate for hydrogen separation with its commercial readiness. However, further investigation in the enhancement of H2/CH4 selectivity is crucial to improve the separation performance. The potential impacts of impurities in HENG on membrane performance are also discussed. The research and development outlook are presented, highlighting the essence of upscaling the membrane separation processes and the integration of membrane technology with pressure swing adsorption technology.

One-pot synthesis of conjugated triphenylamine macrocycles and their complexation with fullerenes.

Triphenylamine derivates have been utilized as building blocks in hole-transporting materials. Herein, we describe the synthesis of three octyl-derived conjugated triphenylamine macrocycles with different sizes, and a 4-(2-ethylhexyloxy)-substituted cyclic triphenylamine hexamer using a palladium-catalyzed C-N coupling reaction. These conjugated triphenylamine macrocycles not only have interesting structures, but also are capable of complexing with C60, C70 and PC61BM. Their binding stoichiometries with fullerenes were all determined to be 1 : 1 by an emission titration method. The association constants of these complexes were measured to be in the range of 0.115-1.53 × 105 M-1 depending on the cavity size of the triphenylamine macrocycles and the volume of the fullerenes. The space-charge-limited current properties of the complexes were further investigated using the fabricated ITO/PEDOT:PSS/active layer/Au devices.

Electrical Double Percolation of Polybutadiene/Polyethylene Glycol Blends Loaded with Conducting Polymer Nanofibers.

The critical phenomena of double percolation on polybutadiene (PB)/polyethylene glycol (PEG) blends loaded with poly-3-hexylthiophene (P3HT) nanofibers is investigated. P3HT nanofibers are selectively localized in the PB phase of the PB/PEG blend, as observed by scanning force microscopy (SFM). Moreover, double percolation is observed, i.e., the percolation of the PB phase in PB/PEG blends and that of the P3HT nanofibers in the PB phase. The percolation threshold (φcI) and critical exponent (tI) of the percolation of the PB phase in PB/PEG blends are estimated to be 0.57 and 1.3, respectively, indicating that the percolation exhibits two-dimensional properties. For the percolation of P3HT nanofibers in the PB phase, the percolation threshold (φcII) and critical exponent (tII) are estimated to be 0.02 and 1.7, respectively. In this case, the percolation exhibits properties in between two and three dimensions. In addition, we investigated the dimensionality with respect to the carrier transport in the P3HT nanofiber network. From the temperature dependence of the field-effect mobility estimated by field-effect transistor (FET) measurements, the carrier transport was explained by a three-dimensional variable range hopping (VRH) model.

Semiconducting Properties of the Hybrid Film of Elastic Poly(styrene-b-butadiene-b-styrene) Block Copolymer and Semiconducting Poly(3-hexylthiophene) Nanofibers.

We investigated the electrical properties of a composite film loaded with semi-conductive poly(3-hexylthiophene) (P3HT) nanofibers dispersed in poly(styrene-b-butadiene-b-styrene) (SBS). This structure can be regarded as the hybrid of SBS matrix with elastic mechanical properties and P3HT nanofibers with semiconducting properties. The P3HT nanofibers were embedded in the fingerprint pattern of microphase-separated SBS, as observed by scanning force microscopy. Furthermore, the electrical conductivity and field-effect mobility of the composite films were evaluated. The field-effect mobility was estimated to be 6.96 × 10-3 cm2 V-1 s-1, which is consistent with the results of previous studies on P3HT nanofibers dispersed in an amorphous polymer matrix including poly(methyl methacrylate) and polystyrene, and we found that the P3HT nanofiber network was connected in the SBS bulk matrix. The film was stretchable; however, at elongation by two times, the nanofiber network could not follow the elongation of the SBS matrix, and the conductivity decreased drastically. The field-effect transistor of this film was operated by bending deformation with a radius of curvature of 1.75 cm, though we could not obtain an off-state and the device operated in a normally-on state.

Single-Component Polycondensation of Bis(alkoxycarbonyldiazomethyl)aromatic Compounds To Afford Poly(arylene vinylene)s with an Alkoxycarbonyl Group on Each Vinylene Carbon Atom.

The original synthetic strategy for a new type of poly(arylene vinylene) (PAV) is presented, where the C=C-bond-forming coupling of bis(alkoxycarbonyldiazomethyl)aromatic compounds is utilized as propagation. The strategy is unique in that the resulting PAVs have an alkoxycarbonyl group as an electron-withdrawing substituent on each vinylene carbon atom in the polymer main chain. Among the transition-metal catalysts examined in this study, RuCl(cod)Cp* (cod = 1,5-cyclooctadiene, Cp* = pentamethylcyclopentadienyl) is the most efficient, affording PAVs from a series of bis(alkoxycarbonyldiazomethyl)aromatic compounds with a high trans-C=C-forming selectivity of up to 90%. A PAV sample with a fluorenylene framework as an arylene moiety prepared by the Ru catalyst exhibited a hole mobility of 4 × 10-6 cm2 V-1 s-1.

Polymer of Intrinsic Microporosity (PIM-1) Membranes Treated with Supercritical CO2.

Polymers of intrinsic microporosity (PIMs) are a promising membrane material for gas separation, because of their high free volume and micro-cavity size distribution. This is countered by PIMs-based membranes being highly susceptible to physical aging, which dramatically reduces their permselectivity over extended periods of time. Supercritical carbon dioxide is known to plasticize and partially solubilise polymers, altering the underlying membrane morphology, and hence impacting the gas separation properties. This investigation reports on the change in PIM-1 membranes after being exposed to supercritical CO2 for two- and eight-hour intervals, followed by two depressurization protocols, a rapid depressurization and a slow depressurization. The exposure times enables the impact contact time with supercritical CO2 has on the membrane morphology to be investigated, as well as the subsequent depressurization event. The density of the post supercritical CO2 exposed membranes, irrespective of exposure time and depressurization, were greater than the untreated membrane. This indicated that supercritical CO2 had solubilised the polymer chain, enabling PIM-1 to rearrange and contract the free volume micro-cavities present. As a consequence, the permeabilities of He, CH4, O2 and CO2 were all reduced for the supercritical CO2-treated membranes compared to the original membrane, while N2 permeability remained unchanged. Importantly, the physical aging properties of the supercritical CO2-treated membranes altered, with only minor reductions in N2, CH4 and O2 permeabilities observed over extended periods of time. In contrast, He and CO2 permeabilities experienced similar physical aging in the supercritical treated membranes to that of the original membrane. This was interpreted as the supercritical CO2 treatment enabling micro-cavity contraction to favour the smaller CO2 molecule, due to size exclusion of the larger N2, CH4 and O2 molecules. Therefore, physical aging of the treated membranes only had minor impact on N2, CH4 and O2 permeability; while the smaller He and CO2 gases experience greater permeability loss. This result implies that supercritical CO2 exposure has potential to limit physical aging performance loss in PIM-1 based membranes for O2/N2 separation.

Microfluidic Fabrication of Morphology-Controlled Polymeric Microspheres of Blends of Poly(4-butyltriphenylamine) and Poly(methyl methacrylate).

Multicomponent polymer particles with specific morphology are promising materials exhibiting novel functionality which cannot be obtained with single-component polymer particles. Particularly, the preparation of such kinds of polymer particles involving electrically or optically active conjugated polymers with uniform size is a challenging subject due to their intense demands. Here, microspheres of binary polymer blend consisting of poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) (1:1 in weight) were produced via a microfluidic emulsification with a Y-shaped microreactor, and a subsequent solvent evaporation method. The flow rate of the dispersed phase (polymer solution) was fixed to 7 µL/min, and 140 or 700 µL/min of the flow rate of the continuous phase (aqueous 0.6 wt % of poly(vinyl alcohol) (PVA) solution) was utilized to produce the dispersion with different diameter. The concentration of dispersed phase was adjusted to 0.1 or 1.0 w/v%. Core-shell, Janus and dumbbell type microspheres were obtained dependent on the flow rate of continuous phase. Incomplete core-shell type microspheres were produced for the blend involving low molecular weight PMMA. Complex Janus and core-shell type microspheres were fabricated by the addition of sodium dodecyl sulfate (SDS) to continuous phase. It is found that final morphologies are strongly dependent on the initial conditions of dispersion including the particle size suggesting that the morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones.

Fabrication of Completely Polymer-Based Solar Cells with p- and n-Type Semiconducting Block Copolymers with Electrically Inert Polystyrene.

It is widely recognized that fullerene derivatives show several advantages as n-type materials in photovoltaic applications. However, conventional [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) exhibits weak absorption in the visible region, and poor morphological stability, due to the facile aggregation. For further improvement of the device performance and durability, utilization of n-type polymeric materials instead of PCBM is considered to be a good way to solve the problems. In this study, we fabricated completely polymer-based solar cells utilizing p- and n-type block copolymers consisting of poly(3-hexylthiophene) (P3HT) and poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)], respectively, containing common polystyrene (PSt) inert blocks, which decreased the size of phase separated structures. Electron mobility in synthesized P(NDI2OD-T2)-b-PSt film enhanced by a factor of 8 compared with homopolymer. The root mean square roughness of the blend film of two block copolymers (12.2 nm) was decreased, compared with that of the simple homopolymers blend (18.8 nm). From the current density-voltage characteristics, it was confirmed that the introduction of PSt into both P3HT and P(NDI2OD-T2) improves short-circuit current density (1.16 to 1.73 mA cm-2) and power-conversion efficiency (0.24% to 0.32%). Better performance is probably due to the uniformity of the phase separation, and the enhancement of charge mobility.

Thermoelectric Properties of Poly(3-Hexylthiophene) Nanofiber Mat with a Large Void Fraction.

The thermoelectric properties of a poly(3-hexylthiophene) (P3HT) nanofiber mat which has higher crystallinity-and thus exhibits larger carrier mobility-than a non-fibrous P3HT film, were investigated. No significant difference was observed in the maximum values of the power factor between the P3HT nanofiber mat and the P3HT film. However, the thermal conductivity of the nanofiber mat was less than half that of the film despite having almost the same electrical conductivity. This higher thermoelectric property of the nanofiber mat than the film is attributed to the existence of highly effective conducting pathways and a large void fraction, and the result means that the nanofiber mat was a good candidate for use as a thermoelectric material.