Search results for "Note"
showing 10 items of 10709 documents
Isostructural compartmentalized spin-crossover coordination polymers for gas confinement
2016
[EN] Here we present two FeII coordination polymers that possess discrete compartments suitable for CO2 physisorption despite the lack of permanent channels. The two crystalline materials, of general formula [Fe(btzbp)3](X)2 (X = ClO4 or BF4), present voids of ca. 250 Å3, which each can accommodate up to two CO2 molecules. The abrupt spin transition can be modified upon CO2 sorption, and different magnetic behaviour is observed depending on the number of molecules sorbed.
Lithium salt additives and the influence of their counterion on the performances of light-emitting electrochemical cells
2016
In this work we study the effect of the addition of lithium salts to light-emitting electrochemical cells (LECs), and in particular the effect of the lithium counterion. We found that the chosen lithium salts can substantially improve the device turn-on time as well as the overall lifetime, with respect to reference LECs using the pure emitter. A correlation between the lithium counterion and the corresponding device performance is established, and efficient LECs with lifetimes approaching 2000 hours are presented.
Different approaches in sulfonated poly (ether ether ketone) conductivity measurements
2019
Ion conductivity of sulfonated poly (ether ether ketone) (SPEEK) membranes with various degree of sulfonation (DS) was investigated using impedance analysis with different measuring cell configuration and ion conductivity was calculated from resistances of polymer membranes. SPEEK was synthesized from poly (ether ether ketone) (PEEK) via sulfonation reaction in concentrated sulfuric acid (95-98%). Scanning electron microscopy (SEM) analysis of membrane surface was performed to determine possible mechanical damage to the membrane during resistance measurements.
Estimation of the elastic constants of highly porous cellular plastics reinforced with fibres embedded in foam struts
2015
In order to enhance the mechanical properties of polymer foams, fillers of different materials and sizes are being applied. Fibrous fillers shorter than the characteristic foam cell dimensions have the potential of efficient reinforcement, due to their high aspect ratio, without detrimentally interfering with foam structure. A theoretical model is developed for evaluation of the effect of filler on foam stiffness. The elastic response of rigid polymer foams filled with short fibres, of length commensurable with that of foam struts, is modelled by using the orientational averaging technique. Explicit expressions for components of the stiffness tensor of composite foams are derived in terms …
Disentangling the Role of Chain Conformation on the Mechanics of Polymer Tethered Particle Materials
2019
[Image: see text] The linear elastic properties of isotropic materials of polymer tethered nanoparticles (NPs) are evaluated using noncontact Brillouin light spectroscopy. While the mechanical properties of dense brush materials follow predicted trends with NP composition, a surprising increase in elastic moduli is observed in the case of sparsely grafted particle systems at approximately equal NP filling ratio. Complementary molecular dynamics simulations reveal that the stiffening is caused by the coil-like conformations of the grafted chains, which lead to stronger polymer–polymer interactions compared to densely grafted NPs with short chains. Our results point to novel opportunities to …
Cellulose Nanocrystals from Lignocellulosic Raw Materials, for Oxygen Barrier Coatings on Food Packaging Films
2017
Cellulose nanocrystals (CNCs) are unique, renewable top-down nano particles from which coatings with improved gas barrier properties and new functionalities can be prepared. In this paper, the potential for obtaining such high performing nanocrystals from low-cost lignocellulosic by-products or raw materials is proved by a comparison study on CNCs obtained both from cotton linters and kraft pulp, by means of the ammonium persulfate (APS) process. Morphological and chemical characterization of the nanocrystals obtained, as well as the main functional properties of the poly(ethylene terephthalate) coated films, showed quite similar characteristics and performances of CNCs obtained from pure c…
Magnetically enhanced polymer-supported ceria nanocatalysts for the hydration of nitriles.
2020
The heterogeneous catalysis of the hydration of nitriles to amides is a process of great industrial relevance in which cerium(IV) oxide (also referred to as ceria) has shown an outstanding catalytic performance. The use of non-supported ceria nanoparticles is related to difficulties in the purification of the product and the recovery and recyclability of the catalyst. Therefore, in this work, ceria nanoparticles are supported on a polymer matrix either by synthesizing polymer particles by so-called Pickering miniemulsions while using ceria nanoparticles as emulsion stabilizers or, as a comparison, by in-situ crystallization on preformed polymer particles. The former strategy presents signif…
Inside Front Cover: Redox-Tunable Defects in Colloidal Photonic Crystals (Adv. Mater. 20/2005)
2005
The inside front cover illustrates reversible tuning of an intragap transmitting state induced by redox cycling, accomplished using a redox-active polyferrocenylsilane polyelectrolyte multilayer planar defect embedded in a colloidal photonic crystal (CPC) synthesized by a bottom–up method combining colloidal self-assembly and microcontact printing. In work reported on p. 2455 by Manners, Ozin, and co-workers, the wavelength position of the defect state can be changed by changing the oxidation state of the ferrocene moieties in the polymer backbone. This could find applications in electrochemically tunable microcavities, and—if light emitters are incorporated—electrochemically tunable CPC-ba…
Formation of nanorods by self-assembly of alkyl-substituted polyphenylene dendrimers on graphite
2000
Alkyl-substituted polyphenylene dendrimers with a tetrahedral or disk-like shape form self-assembled monolayers on graphite (HOPG) which show complex supramolecular structures, such as parallel rods of 6 nm diameter or two-dimensional crystals.
Expanded micro-particles by supercritical antisolvent precipitation: Interpretation of results
2008
Abstract Supercritical antisolvent (SAS) micronization has been used to obtain nanoparticles and micro-particles of several kinds of materials. Sometimes hollow expanded micro-particles have also been obtained. This work is focused on the analysis of this last morphology. We organized literature data and our previous experiments and we added new experiments on previously tested compounds and on compounds never tested before. As a result, expanded micro-particles using several compounds belonging to different categories and precipitated from different solvents in laboratory and pilot scale plants were obtained with diameters between about 10 and 180 μm. They also showed different sub-structu…