Search results for "polymers"
showing 10 items of 3567 documents
Solution processable high band gap hosts based on carbazole functionalized cyclic phosphazene cores for application in organic light‐emitting diodes
2011
A new class of solution processable dendrimers based on cyclic phosphazene (CP) cores have been prepared and used as host materials for blue and green organic light emitting diodes (OLEDs). The dendrimers are prepared in high yield from minimal step reactions, are soluble in common solvents for solution processing, are amorphous, and have excellent thermal properties necessary for application in OLEDs. OLED efficiencies of 10.3 cd/A (4.2 Im/W) and 35.3 cd/A (33.5 Im/W) were achieved using commercially available Flrpic and Ir(mppy) 3 as blue and green phosphorescent emitters, respectively. These efficiencies were 2x higher than control devices prepared using poly(N-vinylcarbazole), the most …
Conducting Polymer with Orthogonal Catechol and Disulfide Anchor Groups for the Assembly of Inorganic Nanostructures
2017
To combine several inorganic components with organic material in a controlled special and permanent manner still remains a difficult issue. Two specifically functionalized block copolymers were synthesized separately and combined in a second step. A heterofunctional poly(ethylene glycol) (PEG) block copolymer bearing a single amino unit, a short PEG spacer, and multiple catechol functionalities was obtained via anionic ring-opening polymerization (AROP). Using the reversible addition–fragmentation chain transfer (RAFT) radical polymerization technique, a semiconducting block copolymer with carbazole side groups was obtained. The second polyacrylate block contained reactive ester groups and …
Tailored conjugated polymer Langmuir-Schafer thin films in sensing transistors
2004
Organic Thin Film Transistors (OTFTs) have been fabricated, in a standard bottom gate configuration, with Langmuir-Schäfer (LS) or cast thin films of regioregular poly[1,4-(2,5-dioctyloxyphenylene)-2,5-thiophene], synthesized via an organometallic protocol, as active layers. The transistors electrical characterization has evidenced that LS based devices exhibit better performance level than cast film ones. Appealing perspectives for newly substituted conjugated polymers in OTFT sensing devices are discussed.
Ester-functionalized poly(3-alkylthiophene) copolymers : synthesis, physicochemical characterization and performance in bulk heterojunction organic s…
2013
Abstract The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opt…
Oligothiophenes for Pattern Formation by Stamping
2003
Oligothiophene monomers with a fixed length varying from 3 to 5 thiophene rings were prepared by Stille coupling. They were functionalised with one or two methacrylate groups to allow polymerization and cross-linking. These monomers can be patterned with the help of soft silicon stamps (e.g., with the micro-injection moulding in capillaries process) on substrates like glass or flexible polymer foils. If a photoinitiator has been added, they can then be hardened by exposure to UV-light through the transparent stamp. Afterwards the stamp can be removed. This allows the preparation of several centimeters long oligothiophene lines of a width varying between 50 and 0.5 μm. These lines of semicon…
Polymer-based symmetric electrochromic devices
1999
Abstract The fact that conjugated polymers repeatedly undergo electrochemical doping/undoping processes, which are accompained by color changes, makes these materials very attractive, and much effort has been devoted to their use in advanced devices. There is renewed interest in electroactive polymers that reversibly undergo both p- and n-doping because of their potential application in symmetric electrochemical devices. We employed fused molecules, dithienothiophenes, as monomers to obtain polymers with a narrow band gap suitable for n- and p-doping. The performance results of two symmetric electrochromic devices having as electrodes both poly(dithieno[3,4-b:3',4'-d]thiophene) (pDTT1) and …
Thermal sensor based on a polymer nanofilm
2016
In this work, we have developed a thermal sensor based on poly(3,4 ethylenedioxythiophene) (PEDOT) nanofilms as thermoelectric material. The PEDOT nanofilms have been synthesized by the electrochemical polymerization method. The thicknesses of the films were around 120 nm. The doping level of PEDOT was controlled by chemical reduction using hydrazine. The achieved Seebeck coeficient is 40 uV/K. A PEDOT nanofilm was integrated into an electronic circuit that amplifies the voltage originated from the Seebeck effect. The temperature increment produced by a fingerprint touching the film is enough to switch on a light emitting diode. Peer Reviewed
Physicochemical and functional characterization of the polymerization process of the Geodia cydonium lectin
1985
The extracellularly localized, galactose-specific lectin from the sponge Geodia cydonium binds at one class of sites, 40 mol Ca2+/mol lectin with an association constant (Ka) of 0.3 X 10(6)M-1. Stoichiometric calculations reveal that in the extracellular milieu 22 mol Ca2+ (maximum) are complexed per mol lectin. Binding of Ca2+ to the lectin increases its apparent Mr from 44000 to 56000 (electrophoretic determination) or from 36500 to 53500 (high-pressure liquid gel chromatographical determination); the s20, w increases from 4.3 S to 4.5 S if Ca2+ is added to the lectin. In the presence of Ca2+ the lectin undergoes a conformational change perhaps by expanding the carbohydrate side chains wh…
Importance of surface tension characterization for food, pharmaceutical and packaging products: a review.
2006
This article reviews the various theoretical approaches that have been developed for determination of the surface tension of solids, and the applications to food industrial products. The surface tension of a solid is a characteristic of surface properties and interfacial interactions such as adsorption, wetting or adhesion. The knowledge of surface tension is thus of great interest for every domain involved in understanding these mechanisms, which recover a lot of industrial investigations. Indeed, it is the case for the packaging industry, the food materials science, the biomedical applications and the pharmaceutical products, cleaning, adhesive technology, painting, coating and more gener…
Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of the wooden part
2020
Abstract: This work follows a previous one dealing with the state of conservation study of the wooden part of the roman Acqualadroni rostrum soon after its finding in the seabed of Acqualadroni (Messina, Italy). The archaeological survey and recovery were particularly relevant since this artefact is one of the two rostrums, nowadays known,found together with its wooden part. Following the recovery, it was consolidated by immersion in a melamine-formaldehyde resin (Kauramin) aqueous solution for eight months at the “Centro di Restauro del Legno Bagnato” (Pisa, Italy). The present investigation is aimed to determine at microscopic scale the wood state of conservation and to highlight interact…