Search

We demonstrate that the lamella-forming polystyrene-block-poly(N-methyl-4-vinylpyridinium iodine) (PS-b-P4VPQ), with similar sizes of the PS and P4VPQ blocks, can be dispersed in the aqueous solutions by forming lipid/PS-b-P4VPQ multilamellae. Using small-angle neutron scattering (SANS) and 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (d62-DPPC) in D2O, a broad correlation peak is found in the scattering profile that signifies the formation of the loosely ordered d62-DPPC/PS-b-P4VPQ multilamellae. The thicknesses of the hydrophobic and hydrophilic layers of the d62-DPPC/PS-b-P4VPQ multilamellae are close to the PS layer and the condensed brush layer thicknesses as determined from previous neutron reflectometry studies on the PS-b-P4VPQ monolayer at the air-water interface. Such well-dispersed d62-DPPC/PS-b-P4VPQ multilamellae are capable of forming multilamellae with DNA in aqueous solution. It is found that the encapsulation of DNA in the hydrophilic layer of the d62-DPPC/PS-b-P4VPQ multilamellae slightly increases the thickness of the hydrophilic layer. Adding CaCl2 can enhance the DNA adsorption in the hydrophilic brush layer, and it is similar to that observed in the neutron reflectometry study of the DNA adsorption by the PS-b-P4VPQ monolayer.

A novel light-emitting monomer M1 and its side-chain polymer P1 containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer P1 to specific metal ions. Among these metal ions, P1 exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of τ(1) decay components in polymer complexes (P1+Ni(2+)) and (P1+Cu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (τ(1)) and the other from free polymer P1 (τ(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer P1 showed faster decay time constants (τ(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyldiethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)) for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.

This work aims to generate maleimides to polymers via Diels–Alder reaction and ring-opening metathesis polymerization (ROMP). Maleimides were converted to adducts through Diels–Alder reactions by reacting with cyclopentadiene or furan, then these adducts were generated to the corresponding polymers via ring-opening metathesis polymerization. The chemical structures of adducts were confirmed by 1H NMR, FTIR and elemental analysis. After investigating the polymerization behaviors and properties, we found that the adducts could be converted into polymers via ROMP and affording polymers exhibited excellent performance. For example, the glass transition temperature of PBMC is 252 °C, 5% and 10% weight loss temperatures are successively 381 °C and 475 °C, and the relative dielectric constant (Dk) and dissipation (Df) at 1 Hz and 1 MHz are respectively 3.41 and 0.006, 3.35 and 0.020. Moreover, the adducts can be used to enhance other ROMP-derived polymers as the comonomers. We believe these may help researchers design and explore novel maleimides polymers and copolymers with promising properties. [ABSTRACT FROM AUTHOR]

This study provides new evidence on a long postulated mechanism of phase separation in a polymer/fullerene mixture during spin coating for controlled nanodomains of oriented crystallization and heterojunctions that favor applications in polymer solar cells (PSCs). The simultaneous nanoscale phase separation and crystallization during spin coating of the mixture are traced using in situ grazing-incidence small- and wide-angle X-ray scattering. Combined with the complimentary results from time-resolved optical reflectance spectroscopy, transient stratification of the liquid film during the transition from the flow- to evaporation-dominated stage of spin coating is disclosed; the vertical liquid-liquid phase separation incubates a supersaturated skin layer where fullerene aggregation and polymer crystallization occur and develop concomitantly. Shortly after the transition, the near-surface structural development is largely pinned, leaving the solvent-rich bottom layer to diminish via solvent diffusion and evaporation through the thickened skin layer that finally condenses into the spin-coated film upon solvent depletion. The shear-enhanced surface layering and supersaturation for the surface-down nanostructural development are unexpected in all the existing structural models for PSCs. The mechanistic understanding of coupled vertical phase separation and local nanosegregation provides new insights and alternative strategy to the morphology control of spin-cast PSC active layers in particular and various solution-processed polymeric films in general. [ABSTRACT FROM AUTHOR]

Abstract: We discovered that fringe structures of ZnO film in solar cells of inverted structures penetrate through the active layer made of low bandgap polymers. The ZnO penetration leads to leakage current of the solar cells. To prevent the ZnO penetration, the thin film morphology was modified. By changing the solvent and inserting TiO2 nanorods between ZnO film and the active layer, penetration can be avoided, so Rsh is improved from 110.3Ωcm2 to 374.7Ωcm2 and V oc from 0.36V to 0.66V. This result provides a promising route for employing low bandgap polymers to air-stable inverted structures with solution process. It is possible that inverted low bandgap polymer solar cells can achieve the goals of high performance and air stability. [Copyright &y& Elsevier]

A pure benzoxazine synthesized from phenolphthalein through Mannich reaction, 3,3′-bis(3,4-dihydro-3-phenyl-2 H-1,3-benzoxazinyl)-1(3 H)-isobenzofuranone (Boz-BP), was characterized by FTIR and H NMR. Its curing behavior was different with that of 2,2′-bis(4-phenyl-3,4-dihydro-2 H-1,3-benzoxazinyl)isopropane (Boz-BA) because Boz-BP possesses highly steric and inactivated phenol rings. During curing period, the reactivity of ortho position of phenolic hydroxyl group was retarded and the addition of -CH- group generated in ring-opening reaction preferred to taking place on para position of aniline ring, which is beneficial for better thermal properties. Furthermore, additional hydrogen bonding would be formed between carbonyl groups on phthalide structure and hydroxyl groups in Boz-BP based polymer (P(Boz-BP)). Compared with the analogous polymer from Boz-BA (P(Boz-BA)), P(Boz-BP) displayed higher glass transition temperature, better thermal stability, better dimensional stability and flame-retardant properties. [ABSTRACT FROM AUTHOR]

Abstract: The selection of carrier transporting layer in polymer solar cells is an important issue because the nature and direction of carrier transport can be manipulated by inserting different functional layers in the device structure. In this work, we report a very efficient inverted polymer solar cell (PSC) system based on regioregular poly(3-hexylthiophene) and a n-type acceptor, bis-indene[C60]. With a pair of metal oxides and the insertion of TiO2 nanorods electron collecting layer between the ZnO thin film and the active layer, the device efficiency can be greatly improved. The contact area between the active layer and the electron collecting layer, as well as the thickness of active layer, can be increased with the incorporation of TiO2 nanorods. As a result, photocurrent can be enhanced due to more absorption of light and more charge separation interface. In addition, the larger contact area and the crystalline TiO2 nanorods provide a more efficient transporting route for the carriers to the cathode. The most efficient device demonstrated shows a high power conversion efficiency of 5.6% with the inverted structure. [Copyright &y& Elsevier]

Abstract: In order to study the photoreactivity and the optical properties of liquid crystalline copolymers with multiple photochromic groups, a series of novel liquid crystalline binary and ternary polyacrylates consisting of one (C:glyph name="dbnd" />N) or dual (Ce:glyph name="dbnd" />N) photochromic segments were synthesized and characterized considering their liquid crystalline, optical, and photochromic properties and their thermal stability. Achiral homopolymer P1 shows a smectic A phase (fan-shaped texture), and all chiral copolymers CP1–CP6 exhibit chiral nematic phases (cholesteric, oily streaks textures). The polymers show excellent solubility in common organic solvents such as chloroform, toluene, and THF. These polymers also exhibit good thermal stability, with decomposition temperatures (T ds) greater than 373°C at 5% weight loss, and beyond 440°C at 50% weight loss under nitrogen atmosphere. UV irradiation caused E/Z photoisomerization at Ne:glyph name="dbnd" />C segments of the synthesized photochromic copolymers leading to reversible and irreversible isomerizations, respectively. The synthesized liquid crystalline ternary copolymer CP6, containing two different photochromic Ne:glyph name="dbnd" />C groups, is sensitive to different UV wavelengths and is notably interesting from the viewpoint of photochromic copolymers. [Copyright &y& Elsevier]

Abstract: To investigate the steric effects of chiral menthyl groups on the induction of cholesteric liquid crystals and the sensitivity of the photoisomerizable azobenzene derivatives, a series of chiral monomers and a photoisomerizable chiral azobenzene derivative with various spacers end-capped with (−)-menthyl group were synthesized. The structures of the novel chiral compounds synthesized in this investigation were identified using 13C NMR, FTIR, and elemental analysis. The phase transition temperatures of the chiral compounds were investigated using X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The thermogravimetric characteristics, the glass-transition temperatures (T g) and the weight–average molecular weights (M w) of the homopolymers were also evaluated. Polymers containing chiral menthyl groups with a biphenyl segment were found to reveal high thermal resistance. However, the existence of the steric hindered menthyl group disturbed the arrangement of chiral monomers leading to the disappearance of liquid crystal phases. The specific optical rotation of the synthesized monomers and polymers were also evaluated. The effect of the synthesized chiral compounds, monomers and photoisomerizable azobenzene derivative on the induction of the cholesteric liquid crystal films was investigated. The morphological network structure of the polymer matrix inside a liquid crystal cell was studied using a scanning electron microscope (SEM). The phototuning ability of the AzoM on the cholesteric liquid crystals was also established. [Copyright &y& Elsevier]

Time‐resolved, grazing incidence small‐ and wide‐angle X‐ray scattering together with in situ UV‐Vis reflectance spectroscopy unveil the surface layering in the early stage of spin‐coating of a polymer‐fullerene mixture, which drives surface‐down local phase separation over the flow‐ to evaporation‐dominated stages of film formation for mutually confined and intercalated nanodomains of polymer crystallites and fullerene aggregates. This is reported by Chun‐Jen Su, U‐Ser Jeng, and co‐workers in article number 1601842. [ABSTRACT FROM AUTHOR]

Abstract: An electric field was externally applied on the poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blend film during the fabrication of the bulk-heterojunction (BHJ) solar cells to induce morphological modification. It influences the vertical ratio of P3HT:PCBM molecules. Because the field is applied externally to the device, its direction can be altered. When the electric field of 5.0×105 Vm−1 was applied with the specific direction, it formed a P3HT-rich and rougher surface, compared with that of pristine active layer, to improve the performance of the inverted polymer solar cells. Hence, the current density was improved from 9.15mAcm−2 to 9.83mAcm−2, and power conversion efficiency increased from 3.16% to 3.51%. This finding provides guidance for morphology engineering in organic materials for higher power conversion efficiency of organic solar cells. [Copyright &y& Elsevier]

Abstract: Molybdenum oxide (MoO X ) has drawn increasing attention in organic photovoltaic cells due to the large performance enhancement achieved in organic light emitting diodes. In this work, we report on inverted polymer photovoltaics (PVs) with solution-processed MoO X as anodic modification to enhance the performance of PVs. MoO3 is reduced to MoO X with x<3 after air-plasma treatment and then plays a role more closely to the thermally deposited MoO X , whose oxygen ratio is reduced during high temperature deposition. The reduced oxygen ratio provides more effective transport, thus enhancing the J SC of the devices. The PCE of the device with solution-processed MoO X is then enhanced to over 4%, which is comparable to that of thermally deposited MoO X . As a result, this work provides good compatibility for deposition of solution-process MoO X on top of polymer:fullerene blends in inverted polymer PVs to achieve better performance. [Copyright &y& Elsevier]