Search results for "optical"
showing 10 items of 7671 documents
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.
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.
Polyisoprene-carbon black nanocomposites as tensile strain and pressure sensor materials
2004
Abstract Electrically conductive polymer composites (ECPC) are shown as prospective large-size flexible pressure and stretch sensors for detecting of dangerous deformations and vibrations of vehicle parts. Reversible change of resistance dependent on stretch and pressure is obtained in electro-conductive polymer nanocomposites. At certain concentrations of carbon nano-particles a change of electrical resistance by more than four orders is observed at 40% relative stretch. The maximum sensitivity of nanocomposites is observed in the vicinity of the transition of electro-conductive percolation. Nanocomposites exhibit a very weak semiconductor-like temperature dependence of resistance. The ten…
Towards completely miscible PMMA nanocomposites reinforced by shear-stiff, nano-mica
2014
Abstract Optimizing the reinforcement of polymers with nanoplatelets requires optimization of the aspect ratio and the moduli of the filler while providing a complete stress transfer. Employing a novel shear-stiff, nano-mica with large aspect ratio, we focus on maximizing the interfacial interaction between filler and matrix. External surfaces of the nano-mica were selectively modified by a polycationic macro-initiator and two PMMA-polymer brushes of length below and above critical entanglement length, respectively, and the mechanical properties of the three PMMA nanocomposites were measured. The multiple electrostatic anchoring groups of the macro-initiator not only provide reliable adhesi…
Luminescent and Magnetoresponsive Multifunctional Chalcogenide/Polymer Hybrid Nanoparticles
2013
Cadmium sulfide/magnetite/polymer multifunctional hybrid nanoparticles are prepared by crystallizing CdS in a controlled manner on the surface of phosphonate-functionalized polystyrene particles with a magnetic core. The supporting polymer magnetoresponsive nanoparticles are produced by a modified miniemulsion polymerization process: a first miniemulsion containing the core monomer (styrene) and a phosphonate-functionalized surface-active monomer is mixed with a second miniemulsion containing magnetite nanoparticles capped with oleic acid and the same surface-active monomer. The chalcogenide formation occurs in situ at the surface of the polymer particles by adding a precipitating agent (so…
Second harmonic generation in self-assembled alternating multilayers of hemicyanine containing polymers and polyvinylamine
1995
Abstract Assembly of noncentrosymmetric multilayers is a facile technique for preparing noncentrosymmetric films avoiding electrical poling procedures and problems from subsequent relaxation of the induced orientational order. A maximum Xzzz of 13 × 10−9 esu was achieved for the assembly of up to six layers. Current problems are the long-term hydrolysation of the hemicyanine nonlinear optical chromophores and the reduction of polar orientation with increasing layer thickness.
Relationship between structure and electroluminescence of oligo(p-phenylenevinylene)s
1998
The preparation of LEDs with poly(p-phenylenevinylene) (PPV) as emitting material is well established, However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-…
Stable Light-Emitting Electrochemical Cells Using Hyperbranched Polymer Electrolyte
2021
The choice of an adequate electrolyte is a fundamental aspect in polymer light-emitting electrochemical cells (PLECs) as it provides the in situ electrochemical doping and influences the performance of these devices. In this study, a hyperbranched polymer (Hybrane DEO750 8500) blended with a Li salt is used as a novel electrolyte in state-of-the-art Super Yellow (a polyphenylenevinylene) based LECs. Due to the desirable properties of the hyperbranched polymer and the homogeneous and smooth films that it forms with the emitting polymer, PLEC with excellent electroluminescent properties are obtained using a pulsed current bias scheme. The devices are very stable, with lifetimes in excess of 2…
Photoresponsive Ferroelectric Liquid-Crystalline Polymers
2007
The photoresponse of ferroelectric smectic side-chain liquid-crystalline (LC) polymers containing a photoisomerizable azobenzene derivative as a covalently linked photochromic side group is investigated. By static measurements in different photostationary states, the effect of trans-cis isomerization on the material's phase-transition temperatures and its ferroelectric properties (spontaneous electric polarization Ps and director tilt angle 0) are analyzed. It turns out that the Curie temperature (transition S C * to S A ) can be reversibly shifted by up to 17 °C. The molecular mechanism of this "photoferroelectric effect" is studied in detail using time-resolved measurements of the dye's o…
Specialty and advanced polymers by carbocationic macromolecular engineering
1993
This study briefly surveys a variety of new advanced polymeric materials and controlled synthetic processes available by carbocationic macromolecular engineering techniques and having potential commercial interest. These recent developments, mainly by living carbocationic polymerization, have led to new opportunities in polymerization process control, and in designing microstructure, functionality, molecular weight and molecular weight distribution (MWD) and thus properties of a wide variety of unique polymer systems. The fundamentals of these new emerging technologies and the novel materials offered by them, such as macromonomers, telechelics, polymers with pendant functional groups (liqui…