| 1. |
- Andersson, Mattias, 1985, et al.
(författare)
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Highly Insulating Polyethylene Blends for High-Voltage Direct-Current Power Cables
- 2017
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 6:2, s. 78-82
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Tidskriftsartikel (refereegranskat)abstract
- The insulation of state-of-the-art extruded high-voltage direct-current (HVDC) power cables is composed of cross-linked low-density polyethylene. Driven by the search for sustainable energy solutions, concepts that improve the ability to withstand high electrical fields and, ultimately, the power transmission efficiency are in high demand. The performance of a HVDC insulation material is limited by its residual electrical conductivity. Here, we demonstrate that the addition of small amounts of high-density polyethylene (HDPE) to a low-density polyethylene (LDPE) resin results in a drastic reduction in DC conductivity. An HDPE content as low as 1 wt % is found to introduce a small population of thicker crystalline lamellae, which are finely distributed throughout the material. The change in nanostructure correlates with a decrease in DC conductivity by approximately 1 order of magnitude to about 10(-15) S m(-1) at high electric fields of 30 and 40 kV mm(-1) and elevated temperature of 70 degrees C. This work opens up an alternative design concept for the insulation of HVDC power cables.
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| 2. |
- Asta, Nadia, et al.
(författare)
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The Use of Model Cellulose Materials for Studying Molecular Interactions at Cellulose Interfaces
- 2023
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 12, s. 1530-1535
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive research on biobased and fiber-based materials, fundamental questions regarding the molecular processes governing fiber-fiber interactions remain unanswered. In this study, we introduce a method to examine and clarify molecular interactions within fiber-fiber joints using precisely characterized model materials, i.e., regenerated cellulose gel beads with nanometer-smooth surfaces. By physically modifying these materials and drying them together to create model joints, we can investigate the mechanisms responsible for joining cellulose surfaces and how this affects adhesion in both dry and wet states through precise separation measurements. The findings reveal a subtle balance in the joint formation, influencing the development of nanometer-sized structures at the contact zone and likely inducing built-in stresses in the interphase. This research illustrates how model materials can be tailored to control interactions between cellulose-rich surfaces, laying the groundwork for future high-resolution studies aimed at creating stiff, ductile, and/or tough joints between cellulose surfaces and to allow for the design of high-performance biobased materials.
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| 3. |
- Brouzet, Christophe, et al.
(författare)
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Size-Dependent Orientational Dynamics of Brownian Nanorods
- 2018
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 7:8, s. 1022-1027
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Tidskriftsartikel (refereegranskat)abstract
- Successful assembly of suspended nanoscale rod-like particles depends on fundamental phenomena controlling rotational and translational diffusion. Despite the significant developments in fluidic fabrication of nanostructured materials, the ability to quantify the dynamics in processing systems remains challenging. Here we demonstrate an experimental method for characterization of the orientation dynamics of nanorod suspensions in assembly flows using orientation relaxation. This relaxation, measured by birefringence and obtained after rapidly stopping the flow, is deconvoluted with an inverse Laplace transform to extract a length distribution of aligned nanorods. The methodology is illustrated using nanocelluloses as model systems, where the coupling of rotational diffusion coefficients to particle size distributions as well as flow-induced orientation mechanisms are elucidated.
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| 4. |
- Cao, Wei, et al.
(författare)
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Dual-Cationic Poly(ionic liquid)s Carrying 1,2,4-Triazolium and Imidazolium Moieties : Synthesis and Formation of a Single-Component Porous Membrane
- 2021
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 10:1, s. 161-166
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Tidskriftsartikel (refereegranskat)abstract
- Both imidazolium and 1,2,4-triazolium cations are important functional moieties widely incorporated as building blocks in poly(ionic liquid)s (PILs). In a classical model, a PIL usually contains either imidazolium or 1,2,4-triazolium in its repeating unit. Herein, via exploiting the slight reactivity difference of alkyl bromide with imidazole and 1,2,4-triazole at room temperature, we synthesized dual-cationic PIL homopolymers carrying both imidazolium and 1,2,4-triazolium moieties in the same repeating unit, that is, an asymmetrically dicationic unit. We investigated their fundamental properties, for example, thermal stability and solubility, as well as their unique function in forming supramolecular porous membranes via a water-initiated phase-separation and cross-linking process. With such knowledge, we identified a water-based fabricate strategy toward air-stable porous membranes from single-component Pits. This study will enrich the design tools and chemical structure library of PILs and expand their application spectrum.
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| 5. |
- Carrick, Christopher, et al.
(författare)
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Immunoselective cellulose nanospheres : a versatile platform for nanotheranostics
- 2014
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 3:11, s. 1117-1120
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a novel route for the preparation and functionalization of perfectly spherical cellulose nanospheres (CNSs), ranging from 100 to 400 nrn with a typical diameter of 160-170 nrn,for use in theranostics. The method of preparation enables both surface and interior bulk functionalization, and this presumably also makes the CNSs suitable for use in end-use applications other than theranostics. Surface functionalization was here demonstrated by antibody conjugation with an antibody specific toward the epidermal growth factor receptor (EGFR) protein, i.e., facilitating interaction with cancer cells having the EGFR. Besides showing specificity, the CNS-antibody conjugates showed a very low nonspecific binding. The CNSs could easily be bulk functionalized by embedding gold nanoparticles in the cellulose sphere matrix during CNS preparation to provide imaging contrast for diagnostic purposes.
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| 6. |
- Feng, S. Z., et al.
(författare)
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Siloxane-Terminated Side Chain Engineering of Acceptor Polymers Leading to Over 7% Power Conversion Efficiencies in All-Polymer Solar Cells
- 2017
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 6:11, s. 1310-1314
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the influence of functional pendent groups on acceptor polymers and photovoltaic properties of all-polymer solar cells (all-PSCs), two novel acceptor polymers containing siloxane-terminated side chains are synthesized and characterized. Increasing the content of siloxane-terminated side chains can reduce pi-pi stacking distance and improve crystalline behavior, yet lead to poorer solubility of the acceptor polymers. By modulating the proper loadings of siloxane-terminated side chains on the acceptor polymers, the PBDB-T:PNDI-Si25 all-PSC attains a maximal power conversion efficiency (PCE) of 7.4% with an outstanding fill factor of 0.68. The results provide, new insights for developing high-performance all-PSCs through functional group engineering on the acceptor polymers, to achieve good solubility, polymer miscibility, and blend morphology.
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| 7. |
- Hufendiek, Andrea, et al.
(författare)
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Fluorescent Covalently Cross-Linked Cellulose Networks via Light Induced Ligation
- 2016
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 5:1, s. 139-143
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Tidskriftsartikel (refereegranskat)abstract
- A facile light-induced procedure for the covalent cross-linking of cellulose at ambient conditions employing the nitrile imine mediated tetrazole-ene cycloaddition (NITEC) reaction is presented. Cellulose-tetrazoles with 2 degrees of substitution (0.14 and 0.23) were synthesized in a solution based transesterification procedure in an ionic liquid. Two bismaleimides with either a trioxatridecane or a dithiodipropionyl backbone were used as cross-linkers to form fluorescent, covalently cross-linked cellulose networks and films, which were characterized by UV/vis spectroscopy, fluorescence spectroscopy, DSC, and TGA. The films showed a broad emission band from 500-700 nm and were thermally stable up to 200 degrees C. Using the bismaleimide with a disulfide moiety as the cross-linker, reductive degradation of the films can be induced. Finally, cellulose-tetrazole was cross-linked in a spatially resolved fashion, providing a strategy for the shaping of films based on renewable resources.
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| 8. |
- Hynynen, Jonna, 1987, et al.
(författare)
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Enhanced Thermoelectric Power Factor of Tensile Drawn Poly(3-hexylthiophene)
- 2019
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 8:1, s. 70-76
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 American Chemical Society. The thermoelectric power factor of a broad range of organic semiconductors scales with their electrical conductivity according to a widely obeyed power law, and therefore, strategies that permit this empirical trend to be surpassed are highly sought after. Here, tensile drawing of the conjugated polymer poly(3-hexylthiophene) (P3HT) is employed to create free-standing films with a high degree of uniaxial alignment. Along the direction of orientation, sequential doping with a molybdenum tris(dithiolene) complex leads to a 5-fold enhancement of the power factor beyond the predicted value, reaching up to 16 μW m-1 K-2 for a conductivity of about 13 S cm-1. Neither stretching nor doping affect the glass transition temperature of P3HT, giving rise to robust free-standing materials that are of interest for the design of flexible thermoelectric devices.
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| 9. |
- Jerlhagen, Åsa, et al.
(författare)
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Self-Catalyzed Hydrolysis of Nitrile-Containing RAFT Chain-Transfer Agent and Its Impact upon Polymerization Control of Methacrylic Monomers
- 2024
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 13:5, s. 565-570
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Tidskriftsartikel (refereegranskat)abstract
- Self-catalyzed hydrolysis upon storage of the common RAFT chain-transfer agent (CTA) 4-cyano-4-[(thiothiopropyl)sulfanyl] pentanoic acid (CTPPA) is confirmed, where the nitrile group is transformed into an amide by catalysis from the adjacent carboxylic acid moiety. The amide-CTA (APP) is found to poorly control molecular weight evolution during polymerization of two methacrylates, methyl methacrylate (MMA) and N,N-(dimethylamino)ethyl methacrylate (DMAEMA), likely due to poor reinitiation speed in the pre-equilibrium. However, when attached to a macromolecule, the impact of this amide moiety becomes insignificant and chain extension proceeds as expected with CTPPA. In light of CTPPA and similarly hydrolyzable CTAs being extensively employed for aqueous polymerizations of methacrylates, these findings highlight the importance of CTA purity when performing RAFT polymerizations.
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| 10. |
- Kang, Na Rae, et al.
(författare)
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Polyaromatic perfluorophenylsulfonic acids with high radical resistance and proton conductivity
- 2019
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 8:10, s. 1247-1251
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Tidskriftsartikel (refereegranskat)abstract
- We report on the straightforward metal-free synthesis of poly(p-terphenyl perfluorophenylsulfonic acid)s by efficient superacid catalyzed Friedel–Crafts polycondensations of commercially available perfluoroacetophenone and p-terphenyl, followed by sulfonation of the pendant pentafluorophenyl groups via a selective and quantitative thiolation-oxidation procedure. The stiff and well-defined polymer structure with precisely sequenced and highly acidic units induces efficient ionic clustering, restricted water uptake and swelling, excellent resistance against radical attack and very high proton conductivity. At 120 °C the conductivity reaches 40 and 232 mS cm-1 at 50 and 90% relative humidity, respectively, which very closely matches the benchmark Nafion NR212 membrane. The properties are further tuned by copolymerizations. Overall, the results demonstrate that these materials possess a very attractive combination of characteristics for use as high-performance proton-exchange membranes for fuel cells and water electrolyzers.
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