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The impact of microplastics (MPs) on the metabolic functions of the liver is currently unclear and not completely understood. To investigate the effects of the administration of MPs on the hepatic metabolism of normal and obese mice, alterations in the lipid, glucose (Glu), and amino acid regulation pathways were analyzed in the liver and adipose tissues of C57BL/6Korl (wild type, WT) or C57BL/6-Lepem1hwl/Korl mice (leptin knockout, Lep KO) orally administered polystyrene (PS) MPs for 9 weeks. Significant alterations in the lipid accumulation, adipogenesis, lipogenesis, and lipolysis pathways were detected in the liver tissue of MP-treated WT and Lep KO mice compared to the vehicle-treated group. These alterations in their liver tissues were accompanied by an upregulation of the serum lipid profile, as well as alterations in the adipogenesis, lipogenesis, and lipolysis pathways in the adipose tissues of MP-treated WT and Lep KO mice. Specifically, the level of leptin was increased in the adipose tissues of MP-treated WT mice without any change in their food intake. Also, MP-induced disruptions in the glycogenolysis, Glu transporter type 4 (GLUT4)-5′ AMP-activated protein kinase (AMPK) signaling pathway, levels of lipid intermediates, and the insulin resistance of the liver tissues of WT and Lep KO mice were observed. Furthermore, the levels of seven endogenous metabolites were remarkably changed in the serum of WT and Lep KO mice after MP administrations. Finally, the impact of the MP administration observed in both types of mice was further verified in differentiated 3T3-L1 adipocytes and HepG2 cells. Thus, these results suggest that the oral administration of MPs for 9 weeks may be associated with the disruption of lipid, Glu, and amino acid metabolism in the liver tissue of obese WT and Lep KO mice. [ABSTRACT FROM AUTHOR]

This paper investigates material interpolation schemes in multi-material topology optimization (MMTO) for magnetic device design. Different interpolations of material properties lead to a non-unique layout and differences in performance, thereby affecting the initial design dependence. However, there is a lack of research on material interpolation in MMTO for the magnetic design problem. In this research, two types of material interpolation schemes are compared: recursive multiphase (RM) and discrete material optimization (DMO). To compare only the effects of material interpolations, the non-convex feasible set of material constraints in RM interpolation schemes were transformed into the convex feasible set by a linear form. The performance profile was employed to obtain the global performance of each interpolation scheme. Examples of the C-core actuator and the permanent magnet actuator (PMA) were applied for performance comparison, and the performance profile indicated that the DMO interpolation scheme is robust to initial material distributions and different material constraints compared to the RM interpolation scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-objective optimization method using an adaptive weight determination scheme and tunneling method. To find the optimum designs that are evenly distributed on the Pareto front, the weights of different objective functions are adaptively determined by using the concept of a hyperplane so that new solutions can be gradually found in the objective space. In addition, to avoid locally optimized solutions that are dominated by other Pareto optimum designs, a tunneling method is employed in the optimization process. To confirm the effectiveness of the proposed method, topology optimization of the magnetic actuator is performed. The magnetic force and volume of the actuator are considered as two conflicting objective functions in the optimization problem, and Pareto optimum solutions that are evenly distributed in the objective space could be obtained. [ABSTRACT FROM AUTHOR]

ABSTRACT High transmittance is an important parameter for polyimide (PI) films used as flexible display substrates. However, thermal treatment during film fabrication can cause an undesired phenomenon affecting color change in the films, which is called haze. Until now, haze formation in PI films has remained mostly unexplored, suggesting that originates in the composition. In this work, the effect of fluorination on haze reduction was investigated. Both experiments and density functional theory calculations suggest that a high degree of fluorination of PI repeating units results in weaker intra/intermolecular conjugations between polymer chains and higher haze resistance in the following order: one fluorinated group (−1.43 eV) > two fluorinated groups (−0.76 eV) > three fluorinated groups (−0.52 eV) > four fluorinated groups (−0.43 eV). The differences in the haze resistance can influence on haziness in the PI films by thermal gradient inside a lab scale cavity in a furnace. The obtained results indicate that slow heat transfer facilitates the manufacturing process to obtain high transparency in PI films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44375. [ABSTRACT FROM AUTHOR]

We report the thermal transition and concomitant morphology change of polyimide films, investigated through dynamic mechanical analyses, thermo-mechanical analyses, and X-ray diffraction spectroscopy. For this study, highly transparent polyimide films composed of 3,4,3′,4′-biphenyltetracarboxylic dianhydride and fluorinated diamines, 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl, are prepared through a solvent-casting method. The films are annealed at different temperatures, and two kinds of reaction solvents (n-methyl-2-pyrrolidone and N,N-dimethylacetamide) for the polyimide precursors are compared. The mechanical analyses during thermal transition along with spectroscopic measurements reveal unusual transition behaviors and morphology differences between the polyimide films at various annealing temperatures. The results can be applied to the quantitative analysis of the imidization ratio in highly imidized polyimides when the films are imidized thermally at temperatures above 300 °C. [ABSTRACT FROM AUTHOR]

To understand and optimize the performance of thin-film electronic devices incorporating crystalline organic semiconductors, it is important to consider the impact of their structural anisotropy on the charge transport. Here we report on the charge mobility anisotropy in 6,13-bis(triisopropylsilylethynyl) (TIPS) and 6,13-bis(triethylsilylethynyl) (TES) pentacene field effect transistors, in which microstructure is controlled by solution processing conditions. Thin-film structures that range from millimetre size, crystalline domains to macroscopic, high-aspect-ratio (∼1 μm wide and >1 cm long) needles are systematically produced by controlling the substrate displacement rate during zone-cast deposition. Through precise control of the microstructure we experimentally explore the differences in charge transport anisotropy between TIPS- and TES-pentacene molecules. Aligned needles of TIPS- pentacene result in a mobility anisotropy (μ/μ⊥) of ∼20 (mobility of ∼0.7 cm2 V−1 s−1) whereas TES-pentacene produce an order of magnitude lower mobility (∼0.06 cm2 V−1 s−1) but much higher mobility anisotropy (>45). Such significant changes in absolute mobility and mobility anisotropy are attributed to their different packing structures, which permit 2D charge transport in TIPS-pentacene and 1D transport in TES-pentacene. Bulky TIPS- side groups (diameter ∼7.5 Å) force a brick-wall type packing structure, whereas TES- side groups (diameter ∼6.6 Å) pack in a 1D slipped-stack. Furthermore, through precise control of the molecular alignment, the impact of crystal orientation on charge transport is investigated. TIPS-pentacene achieves the highest mobility when the angle between the needle long-axis and charge transport directions is ∼35°, whereas in TES-pentacene it is much closer to 0°. These results are supported by theoretical simulations. [ABSTRACT FROM AUTHOR]

The authors elucidate an origin and probable mechanism of adhesion strength change at an interface of fluorinated poly(amic acid) and stainless steel. Fluorination provides favorable delamination with release strength weaker than 0.08 N/mm from a metal surface, once the amount of residual solvent becomes less than 35 wt. %. However, the release strength critically depends on film drying temperature. Characterization on stainless steel surfaces and thermodynamic analyses on wet films reveal a drying temperature of 80 °C fosters interaction between the metal oxides at stainless steel surface and the free electron donating groups in poly(amic acid). [ABSTRACT FROM AUTHOR]

Toughness and high elastic elongation are important requirements for polyimide films used as substrates in flexible displays. However, these properties can be altered by imidization during the thermal treatment. In the present study, we investigated a probable mechanism to enhance the toughness by shrinking fluorinated polyimide films containing benzidine moieties. A higher degree of fluorination leads to weaker intermolecular charge transfer and optically clearer films, but it also degrades the mechanical properties. Moreover, β -transition originating from the molecular rotation around benzidines makes the film dependent on the elongation conditions during solvent drying. According to frequency-sweeping measurements and simulations based on density functional theory and molecular dynamics, the β -transition temperature increases and the phase lag in elastic energy loss decreases with increasing shrinkage. Both experimental and theoretical findings suggest that the change in frequency dependence can be attributed to the variation in elasticity retardation, which possibly originates from the chain-entanglement density. [ABSTRACT FROM AUTHOR]

In capacitive deionization, the salt-adsorption capacity of the electrode is critical for the efficient softening of brackish water. To improve the water-deionization capacity, the carbon electrode surface is modified with ion-exchange resins. Herein, we introduce the encapsulation of zwitterionic polymers over activated carbon to provide a resistant barrier that stabilizes the structure of electrode during electrochemical performance and enhances the capacitive deionization efficiency. Compared to conventional activated carbon, the surface-modified activated carbon exhibits significantly enhanced capacitive deionization, with a salt adsorption capacity of ∼2.0 × 10 -4 mg/mL and a minimum conductivity of ∼43 μS/cm in the alkali-metal ions solution. Encapsulating the activated-carbon surface increased the number of ions adsorption sites and the surface area of the electrode, which improved the charge separation and deionization efficiency. In addition, the coating layer suppresses side reactions between the electrode and electrolyte, thus providing a stable cyclability. Our experimental findings suggest that the well-distributed coating layer leads to a synergistic effect on the enhanced electrochemical performance. In addition, density functional theory calculation reveals that a favorable binding affinity exists between the alkali-metal ion and zwitterionic polymer, which supports the preferable salt ions adsorption on the coating layer. The results provide useful information for designing more efficient capacitive-deionization electrodes that require high electrochemical stability.

For efficient solar cells based on organic semiconductors, a good mixture of photoactive materials in the bulk heterojunction on the length scale of several tens of nanometers is an important requirement to prevent exciton recombination. Herein, we demonstrate that nanoporous titanium dioxide inverse opal structures fabricated using a self-assembled monolayer method and with enhanced infiltration of electron-donating polymers is an efficient electron-extracting layer, which enhances the photovoltaic performance. A calcination process generates an inverse opal structure of titanium dioxide (<70 nm of pore diameters) providing three-dimensional (3D) electron transport pathways. Hole-transporting polymers was successfully infiltrated into the pores of the surface-modified titanium dioxide under vacuum conditions at 200 °C. The resulting geometry expands the interfacial area between hole- and electron-transport materials, increasing the thickness of the active layer. The controlled polymer-coating process over titanium dioxide materials enhanced photocurrent of the solar cell device. Density functional theory calculations show improved interfacial adhesion between the self-assembled monolayer-modified surface and polymer molecules, supporting the experimental result of enhanced polymer infiltration into the voids. These results suggest that the 3D inverse opal structure of the surface-modified titanium dioxide can serve as a favorable electron-extracting layer in further enhancing optoelectronic performance based on organic or organic-inorganic hybrid solar cell.

Imidazolium ionic side-group-containing fluorene-based conjugated polyelectrolytes (CPEs) with different π-conjugated structures, poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (F8im-Br) and poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-(benzo(2,1,3)thiadiazol-4,8-diyl) dibromide (F8imBT-Br), are synthesized and utilized as an electron injection layer (EIL) in green-emitting F8BT polymer light-emitting diodes (PLEDs). Both CPE EIL devices significantly outperform Ca cathode devices; 17.9 cd A(-1) (at 3.8 V) and 16.6 lm W(-1) (at 3.0 V) for F8imBT-Br devices, 11.1 cd A(-1) (at 4.2 V) and 9.1 lm W(-1) (at 3.4 V) for F8im-Br devices, and 7.2 cd A(-1) (at 3.6 V) and 7.0 lm W(-1) (at 3.0 V) for Ca devices. Importantly, unlike the F8im-Br EIL devices, F8imBT-Br PLEDs exhibit much faster electroluminescence turn-on times (<10 μs) despite both EILs possessing the same tethered imidazolium and mobile bromide ions. The F8imBT-Br devices represent, to the best of our knowledge, the highest efficiency in thin (70 nm) single-layer F8BT PLEDs in conventional device architecture with the fastest EL response time using CPE EIL with mobile ions. Our results clearly indicate the importance of an additional factor of EIL materials, specifically the conjugated backbone structure, to determine the device efficiency and response times.

Through hydrolysis and polycondensation of amino-silane with alkyl bridged silane, a new type of polysilsesquioxane (PSSQ) was obtained. Here we use amine functionalized silane and bis(silyl)ethane to synthesize alkyl chain linked PSSQ. Compared to conventional polyhedral oligomeric silsesquioxane (POSS), this new silane compound has both enhanced thermal stability and improved compatibility with poly(amic acid). Gelation of this silane compound with poly(amic acid) provides polyimide-organosilicate composite materials. We show that films made from solutions of the composites exhibit higher optical transparency and superior dimensional stability during thermal treatment than films of pure polyimide or of polyimide composites with conventional POSS. Bridging of POSS and chemical bonding between POSS and polyimide chains significantly enhance the physical properties. These results provide useful information for designing molecular architecture for the fabrication of high-performance plastic substrates in the future display devices.

The large-scale manufacture of organic electronics devices becomes more feasible if the molecular orientation and morphology of the semiconductor can be controlled. Here, we report on a previously unidentified crystal shape of terraced nanoscale "ribbons" in thin films of poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT). The ribbons form after a pBTTT film is heated above its highest temperature phase transition. In contrast to the wide terrace crystal shape previously reported, terraced ribbons have lateral widths of approximately 60 nm and lengths greater than 10 microm, with a common orientation between adjacent ribbons. Further, we report a simple and scalable flow coating process that can control the ribbon orientation without requiring special substrates or external fields. The degree of molecular orientation is small after coating but increases dramatically after the terraced ribbons are formed, indicating that an oriented minority templates the whole film structure. The large extent of orientation obtained in these polythiophene crystallites provides potential opportunities to exploit anisotropic electrical properties and to obtain detailed information about the structure of organic semiconductor thin films.

The measurement and optimization of microstructure development in organic semiconductor films is valuable because microstructure in many cases critically impacts electronic performance. We demonstrate a general method to measure microstructure thickness dependence in thin films using surface-sensitive near edge X-ray absorbance fine structure (NEXAFS) spectroscopy. The method is applied to an oligofluorene derivative DDFTTF, which consists of a fluorene-bithiophene-fluorene core that is end-substituted with linear dodecyl groups. The substrate-relative orientations of the aromatic core and the aliphatic end chains are independently determined, and comparing these orientations to terrace heights from atomic force micrographs proves that the end chains are interdigitated or folded. By measuring microstructure development from 6 to 150 nm, we find that DDFTTF exhibits two different preferential microstructures: one with large terraces within which molecules exhibit a strongly vertical orientation, and one with much smaller domains within which molecules exhibit a mildly horizontal orientation. The relative distribution of these two preferential microstructures depends on the distance of the domains from the substrate and the substrate temperature during deposition. The utility of this method is tested using a lamination technique to measure the saturation hole mobility at the top and bottom interface of DDFTTF films. We find that local microstructures with greater pi orbital alignment in the source-drain plane correlate directly to better local saturation hole mobilities.

The thin film microstructure development of functionalized oligothiophenes with branched, thermally removable groups at each end of conjugated cores with five, six, and seven thiophene rings was monitored during their thermal conversion from solution processible precursors to insoluble semiconductor products. The change in end group character provides a comparison of branched vs linear end group functionalization in oligothiophenes. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy confirmed that branched alpha-, omega-substitutions of the precursors strongly influenced the packing of the conjugated core. The quinque- and sexithiophene precursors oriented perpendicular to the substrate, whereas the septithiophene precursor oriented parallel to the substrate, providing one of the first examples of length dependence in oligothiophene orientation. This dependence may be due to a packing mismatch between the conjugated cores and the branched end groups. The convertible septithiophene exhibits four distinct microstructures as it converts from precursor to product that correlate strongly with its field-effect hole mobility in field-effect transistors. The extent of septithiophene order and the surface-relative orientation of its ordered phases clearly influence field-effect transistor performance.