Search results for "rare"
showing 10 items of 2778 documents
Dye-containing S∗cside-on/end-on copolymers
1995
Abstract Mesomorphic copolysiloxanes, which combine ‘normal’ end-on linked chiral mesogenic units inducing S∗c phases and side-on fixed chromophores were prepared. The interplay of the different orientational tendencies of these moieties, which are perpendicular (end-on linked mesogenic groups) or parallel (side-on fixed chromophores) to the polymer chain, lead to a strong destabilization of the S∗c phase. However, copolymers with up to about 10 mol % of chromophores still show a smectic C∗ phase. FTIR measurements show that both moieties orient parallel to each other and perpendicular to the polymer chains. These copolymers are interesting to consider as coloured guest-host S∗c materials f…
Covalently attached polymer mono- and multilayers on silanized glass substrates
1996
Abstract Applying grazing incidence FTIR and ellipsometry, the reaction of poly [(1-methyl-vinyl isocyanate)-alt-(maleic anhydride)](IAP) with amino-silanized glass and silicon oxide surfaces has been investigated. A reactive surface containing isocyanate and anhydride groups was formed after the adsorption of the polymer. The layer could be further functionalized using 2-aminoethanol. Multilayers could be built up by adsorbing a second layer of IAP onto an already reacted first layer of IAP.
Molecular Iodine for a General Synthesis of Binary and Ternary Inorganic and Hybrid Organic-inorganic Iodide Nanocrystals
2018
We report the synthesis of various binary and ternary inorganic and hybrid organic–inorganic iodide nanocrystals (NCs) starting from molecular iodine (I2). The synthesis described herein utilizes a reaction between I2 and oleylamine, which results in oleylammonium iodide, an iodide precursor that can be directly used in the preparation of iodide-based NCs. The generality of the synthesis was demonstrated by synthesizing KI, RbI, CsI, AgI, CsPbI3, FAPbI3, Cs4PbI6, Cs3Bi2I9, FA3Bi2I9, and RbAg4I5 NCs. Furthermore, the syntheses are facile and are carried out in vials heated on a hot plate in air. They exhibit not only narrow size distributions, but also, in the case of lead-based perovskites …
Superhydrophobic TiO2/Fluorinated Polysiloxane Hybrid Coatings with Controlled Morphology for Solar Photocatalysis
2021
Abstract Technological applications of polysiloxane coatings have been influenced by their intrinsic low surface energy, which increases their water repellence. Accurate control of composition and interfacial properties through the introduction of perfluorinated moieties further lowers the polysiloxane surface energy, while mixing with metal oxide nanoparticles enhances roughness, resulting in a great potential in the development of superhydrophobic materials for photocatalysis. Herein, a series of hydrophobic and superhydrophobic hybrid coatings were prepared by dehydrocoupling and hydrosilylation reactions of polymethylhydrosiloxane with 1H,1H,2H,2H‐perfluorooctyltriethoxysilane and 1,3-d…
Physicochemical Properties of Copper(II) Bis(2-ethylhexyl) Sulfosuccinate Reversed Micelles
1998
Abstract Measurements of some physicochemical properties (density, viscosity, conductance, UV–vis spectra, IR spectra) of the water/copper(II) bis(2-ethylhexyl) sulfosuccinate (Cu(DEHSS) 2 )/CCl 4 microemulsions, at a fixed surfactant molal concentration ([Cu (DEHSS) 2 ] = 0.05003 mol kg −1 ), as function of the molar ratio R ( R = [water]/[DEHSS − ]) have been performed at 25°C. Information on some structural and dynamical properties of the water-containing Cu(DEHSS) 2 reversed micelles and of their evolution with R are derived from the experimental results. The comparison with the same properties of water-containing sodium bis(2-ethylhexyl) sulfosuccinate reversed micelles allows to evide…
Barrier, structural and mechanical properties of bovine gelatin-chitosan blend films related to biopolymer interactions
2014
BACKGROUND The increased use of synthetic packaging films has led to a high ecological problem due to their total non-biodegradability. Thus, there is a vital need to develop renewable and environmentally friendly bio-based polymeric materials. Films and coatings made from polysaccharide polymers, particularly chitosans and gelatins have good gas barrier properties and are envisaged more and more for applications in the biomedical and food fields, as well as for packaging. In this study a casting method was used to develop an edible plasticised film from chitosan and gelatin. Aiming to develop a blend film with enhanced properties, the effects of mixing chitosan (CS) and gelatin (G) in diff…
Photosensitive functionalized surface-modified quantum dots for polymeric structures via two-photon-initiated polymerization technique.
2015
In this paper, the surface modification of CdSe- and CdZnS-based quantum dots (QDs) with a functional silica shell is reported. Functionalized silica shells are prepared by two routes: either by ligand exchange and a modified Stober process or by a miniemulsion process with amphiphilic poly(oxyethylene) nonylphenylether also know as Igepal CO-520 (IG) as oligomeric amphiphile and modified silica precursors. The polymerizable groups on the functionalized silica shell allow covalent bonding to a polymer matrix and prevent demixing during polymerization and crosslinking. This allows the homogeneous incorporation of QDs in a crosslinked polymer matrix. This paper furthermore demonstrates that t…
Intensities and electronic transition strengths of seven Te2 visible and i.r. band systems
1992
Abstract We present an experimental study of relative intensity distributions in the laser-flourescence spectra of the AO+u-XO+g, AO+u-X1g, AO+u-b1∑+g, A1-u-X1-g, BO+u-XO+g, BO+u-X1g, and BO+u-b1∑+g systems of the 130Te2 molecule. Effective internuclear potentials have been determined by applying the RKR-procedure and accounting for rovibronic interaction. Franck-Condon factors and r-centroids have been calculated and tabulated. By combining expiremental results and calculations, we obtain the dependence of the electronic transition strength on internuclear distance in the r-centroid approximation. Normalization over the lifetimes of the rovibronic levels of the excited electronic states en…
High-energy radiation processing, a smart approach to obtain PVP-graft-AA nanogels
2014
Abstract Poly(N-vinylpyrrolidone)-grafted-acrylic acid biocompatible nanogels (NGs) were prepared using an exiting industrial-type electron accelerator and setups, starting from semi-dilute aqueous solutions of a commercial PVP and the acrylic acid monomer. As a result, NGs with tunable size and structure can be obtained quantitatively. Sterility was also imparted at the integrated dose absorbed. The chemical structure of the NGs produced was confirmed through Fourier Transformer Infrared Spectroscopy (FT-IR). The molecular and physico-chemical properties of NGs, such as the hydrodynamic dimensions and surface charge densities, for various polymer and monomer concentrations in the irradiate…
Dilute solution properties of polybutadiene modified by 4-phenyl-1,2,4-triazoline-3,5-dione
1996
The dilute solution properties of 4-phenyl-1,2,4-triazoline-3,5-dione-modified polybutadienes were studied in tetrahydrofuran by static and dynamic light scattering and compared with those from unmodified polybutadiene chains. For the unmodified polymer, the scaling laws were established and the coil interpenetration parameter k f0 was determined in the thermodynamically good solvent tetrahydrofuran ; the chains exhibited common flexible chain behavior. For the modified polybutadiene, the results indicate at infinite dilution a weak extent of intermolecular crosslinking via the urazole groups, coupled with a very high extent of intramolecular ring formation. In order to evaluate the fractio…