Abstract Wir beobachteten eine effiziente Induktion von Chiralität in dünnen Polyfluoren‐Copolymer‐Dünnschichten durch Mischen mit chiralen Additiven vom Helicen‐Typ basierend auf dem Dibenzo c , h ...acridin‐Motiv. Bilder, die mittels Circulardichroismus (CD)‐ und zirkular polarisierter Lumineszenz (CPL)‐Mikroskopie erhalten wurden, liefern Informationen zu den chiralen Anordnungen in den dünnen Schichten mit beugungsbegrenzter Auflösung. Das CD‐Signal zeigt eine charakteristische Abhängigkeit von der Filmdicke, was für einen supramolekularen Ursprung der starken chiralen Antwort des Copolymers spricht. Insbesondere demonstrieren wir die Unterscheidung zwischen Filmen mit entgegengesetzter Chiralität auf Basis ihrer ultraschnellen transienten chiralen Antwort mit Hilfe von Femtosekunden‐Breitband‐CD‐Spektroskopie und einem neu entwickelten Aufbau für die transiente CPL‐Spektroskopie mit 28 ps Zeitauflösung. Eine systematische Variation des Enantiomeren‐Überschusses des chiralen Additivs zeigt, dass das “Feldwebel und Soldaten”‐Konzept und die “Mehrheitsregeln” nicht eingehalten werden.
The paper describes the studies on the thermo-oxidative decomposition behavior of two types of starch graft copolymers: starch-g-poly(citronellyl acrylate) copolymers with the grafting percent (%G): ...21.3% ± 0.5, 35.8% ± 0.6 and 59.8% ± 0.3 and starch-g-poly(citronellyl methacrylate) copolymers with %G: 21.3% ± 0.4, 37.0% ± 0.2 and 51.8% ± 0.3 prepared applying the "grafting from" method. The decomposition course of copolymers by using the TG/DTG/DSC/FTIR analysis was evaluated. As it was found, the course of TG/DTG/DSC curves was independent on the %G but it was directly dependent on the type of analyzed copolymer. It resulted in completely different decomposition course of starch-g-poly(citronellyl acrylate) copolymers under the presence of oxidative conditions as compared to starch-g-poly(citronellyl methacrylate) copolymers. Thanks to applying the FTIR analysis of the gaseous products emitted under the heating of the studied materials, the detailed decomposition course of copolymers was evaluated.
The most important class of polymers is block copolymers (BCPs) since they can be prepared through different methods and exhibit various properties combined with chemically different segments. The ...importance of block copolymers can be supported by the multitude of related manuscripts published daily, their use in practical applications in almost all areas, and novel discoveries based on BCPs in many aspects of life. This Special Issue focuses on various matters from different areas of block copolymer research, showing advances and applications in self-assembly, crystallization, synthesis, chemical modification, 3D printing, membranes, energy materials, nanotechnology, hybrid materials, micelles, order–disorder transition, and biomaterials.
7.7% Efficient All-Polymer Solar Cells Hwang, Ye-Jin; Courtright, Brett A. E.; Ferreira, Amy S. ...
Advanced materials (Weinheim),
August 19, 2015, Letnik:
27, Številka:
31
Journal Article
Recenzirano
By controlling the polymer/polymer blend self‐organization rate, all‐polymer solar cells composed of a high‐mobility, crystalline, naphthalene diimide‐selenophene copolymer acceptor and a ...benzodithiophene‐thieno3,4‐bthiophene copolymer donor are achieved with a record 7.7% power conversion efficiency and a record short‐circuit current density (18.8 mA cm−2).
Poly(N-vinylcaprolactam) (PNVCL) is a temperature-responsive polymer, only second to poly(N-isopropylacrylamide), the most popular temperature-responsive polymer. Its applications include its use in ...cosmetics, as an anticlogging agent in pipelines and increasingly, in biomedical applications. This review highlights the controlled synthesis of PNVCL in different architectures: random copolymers, block copolymers, graft copolymers, nanogels, and their applications in the biomedical field, e.g., drug delivery, cell detachment, entrapment of enzymes, tissue engineering, among others. Emerging applications in areas that are expected to grow are also presented where PNVCL will play a pivotal roll: nanotechnology and the environment.
Dielectric, thermal, and electrocaloric investigations of poly(vinylidene fluorideatrifluoroethylene) P(VDFaTrFE) copolymer, irradiated with high-energy electrons, are reported. While the ...ferroelectric copolymer is transformed into a relaxor system at high irradiation doses, dielectric investigations, particularly nonlinear dielectric experiments, i.e., temperature dependences of the second and the third harmonic dielectric response, clearly evidence that at lower doses ferroelectric and relaxor states coexist in the P(VDFaTrFE). This is confirmed by the differential scanning calorimetry, which further reveals the influence of irradiation on the copolymer crystallinity and melting point. Finally, it is shown that large electrocaloric response of VDFaTrFE-based polymers is further enhanced in systems with coexisting relaxor and normal ferroelectric states.
In this contribution, we report the synthesis of organic-inorganic random polymers from methacrylate-terminated poly(ethylene oxide) (MAPEO) (M sub(n) = 950) and 3-methacryloxypropylheptaphenyl ...polyhedral oligomeric silsesquioxane (MAPOSS) macromers viareversible addition-fragmentation chain transfer (RAFT) polymerization with 4-cyano-4-(thiobenzoylthio) valeric acid (CTBTVA) as the chain transfer agent. The organic-inorganic random copolymers were characterized by means of super(1)H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results of GPC indicate that the polymerizations were carried out in a controlled fashion. Transmission electron microscopy (TEM) showed that the organic-inorganic random copolymers in bulk were microphase-separated and the POSS microdomains were formed viaPOSS-POSS interactions. In aqueous solutions the organic-inorganic random copolymers were capable of self-assembling into spherical nanoobjects as evidenced by transmission electron microscopy (TEM) and dynamic laser scattering (DLS). The self-assembly behavior of the organic-inorganic random copolymers was also found to occur in the mixtures with the precursors of epoxy. The nanostructures were further fixed viasubsequent curing reaction and thus the organic-inorganic nanocomposites were obtained. The formation of nanophases in epoxy thermosets was confirmed by transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The organic-inorganic nanocomposites displayed the enhanced surface hydrophobicity as evidenced by surface contact angle measurements.
In this paper, by optimizing synthesis process of α,ω-hydroxyalkyl telechelic polydimethylsiloxane, α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane (PMTS), the yield of ...hydrosilylation product, 1,3-bis(glycidoxypropyl) tetramethyldisiloxane exceed 86.5%. By tracing the change of methanol (gravimetry) and measuring the change of molecular weights of polydimethylsiloxanes at different reaction time (titration), the optimum reaction time of methoxylation reaction and ring-opening polymerization was determined as 8 and 12 h. Using α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane with different molecular weights, waterborne polyurethane-polydimethylsiloxane block copolymer were prepared. The influences of molecular weights and content of α,ω-hydroxyalkyl telechelic polydimethylsiloxane on the waterborne polyurethane-polydimethylsiloxane block copolymers were investigated in detail. The addition of α,ω-hydroxyalkyl telechelic polydimethylsiloxane could improve the water-resistance property obviously and increase the elongation at break. However, the mechanical property was reduced with increase of content and molecular weight of α,ω-hydroxyalkyl telechelic polydimethylsiloxane.
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![Synthesis of [alpha],[omega...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0169-4243/small "Synthesis of [alpha],[omega]-hydroxyalkyl telechelic polydimethylsiloxane soft segments and preparation of waterborne polyurethane-polydimethylsiloxane block copolymers")