Search results for "silsesquioxane"
showing 10 items of 65 documents
MEMS analogous micro-patterning of thermotropic nematic liquid crystalline elastomer films using a fluorinated photoresist and a hard mask process
2017
In this work, we present a method to pattern liquid crystal elastomers (LCEs) in the micrometer range without using any mechanical processing steps to prepare micron sized LCE actuators compatible with microelectromechanical system (MEMS) technology. Multi-layer spin-coating processes are developed to synthesise and structure 300–3500 nm thick LCE films. A water soluble sacrificial layer, a photoalignment layer and a LCE formulation, which is polymerised and crosslinked in its liquid crystal phase, are spin-coated successively onto a substrate. A fluorinated photoresist layer is used to structure LCE films with thicknesses up to 700 nm in a photolithographic and etching process. For thicker…
Study of polyethylene nanocomposites with polyhedral oligomeric silsesquioxane nanofillers—from structural characteristics to mechanical properties a…
2017
High-density polyethylene (HDPE) and low-density polyethylene (LDPE) nanocomposites filled with octakis({alkyl}dimethylsiloxy)octasilsesquioxanes (POSS) were prepared by the melt blending method. The effects of the structure and the content of POSS nanofillers on free-volume properties and structural characteristics of nanocomposites were investigated by the positron annihilation lifetime spectroscopy (PALS) and X-ray diffraction methods: wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Incorporation of POSS nanofillers into polyethylene matrices modified the arrangement of the polymer chains and affected the size and number of free-volume holes in nanocomposites.…
On the role of multi-functional polyhedral oligomeric silsesquioxane in polystyrene-zinc oxide nanocomposites
2014
Abstract Multi-functional trisilanol phenyl (TSPH) and trisilanol isobutyl (TSIB) polyhedral oligomeric silsesquioxane (POSS) have been used in the formulation of advanced polystyrene (PS)-zinc oxide (ZnO) nanocomposites. The neat matrix and PS/ZnO-based nanocomposites have been characterized through rheological, morphological, mechanical, and dynamic thermo-mechanical analysis. Both TSPH and TSIB are able to improve the dispersion of ZnO into the polystyrene matrix; furthermore, adding TSIB leads to better results because it facilitates better solubility into the PS matrix and interaction/reaction with the ZnO nanopowder. Finally, the optical properties and photo-oxidative resistance of th…
Highly untangled multiwalled carbon nanotube@polyhedral oligomeric silsesquioxane ionic hybrids: Synthesis, characterization and nonlinear optical pr…
2015
Abstract Highly de-bundled multiwalled carbon nanotube (MWCNT) polymer nanohybrids were obtained via ionic assembling of a novel POSS-polyimidazolium-ionic liquid (POSS = polyhedral oligomeric silsesquioxanes) with oxidized MWCNTs. The synthesis, accomplished by a simple bilayer chloroform/water metathetical reaction process, was promoted by the high surfactant properties of POSS-imidazolium-polyionic liquid, which assisted the effective de-bundling, dispersion and purification of the as prepared POSS@MWCNT polymers in organic media, via a surface coating mechanism. The presence of remarkably intense radial breathing modes (RBMs) in Raman spectra, both in solution and as solid, corroborates…
Adhesion of proton beam written high aspect ratio hydrogen silsesquioxane (HSQ) nanostructures on different metallic substrates
2009
Abstract Hydrogen silsesquioxane (HSQ) behaves as a negative resist under MeV proton beam exposure. HSQ is a high-resolution resist suitable for production of tall (
Proton beam written hydrogen silsesquioxane (HSQ) nanostructures for Nickel electroplating
2009
Abstract Hydrogen silsesquioxane (HSQ) behaves as a negative resist under MeV proton beam exposure. HSQ is a high-resolution resist suitable for production of tall ( 1.5 μ m ) high-aspect-ratio nanostructures with dimensions down to 22 nm. High-aspect-ratio HSQ structures are required in many applications, e.g. nanofluidics, biomedical research, etc. Since P-beam writing is a direct and hence slow process, it is beneficiary to fabricate a reverse image of the patterns in a metallic stamp, e.g. by Ni electroplating. The Ni stamp can then be used to produce multiple copies of the same pattern. In this study we investigate the possibility to produce Ni stamps from p-beam written HSQ samples. H…
One-step reactive processing of low density polyethylene and octavinyl polyhedral oligomeric silsesquioxane
2015
Polyhedral oligomeric silsesquioxane (POSS) are an innovative class of organosilicon compounds suitable for formulation of advanced organic-inorganic hybrid materials. Nanocomposites based POSS found application mostly in high-temperature resistance and fire-resistance materials. POSS are characterized by a three dimensional cage-like structure, made of Si-O bonds, with different organic groups directly linked to the Si atoms of the cage structure. The organic groups can be designed to facilitate the dispersion of the nanoparticle itself in the polymer matrix or also to react with the polymer chain. This work focuses on the possibility to obtain crosslinking of polyethylene using octavinyl-…
Chemically selective imaging of overlapping C-H stretching vibrations with time-resolved coherent anti-stokes Raman scattering (CARS) microscopy.
2014
Chemically selective imaging of spectrally overlapping compounds is studied with a time-resolved, femtosecond approach on coherent anti-Stokes Raman scattering (CARS) microscopy taking advantage of time-dependent oscillating CARS amplitude which is sensitive to different chemical components at different time points. Chemically selective imaging is demonstrated for composite material of polypropylene (PP) matrix and om-POSS (octamethyl polyhedral oligomeric silsesquioxane) microparticles having partly overlapping CH stretching vibrations. Inverse Fourier transformation (IFT) was applied to Raman spectra of PP and om-POSS, indicating that the oscillatory structures of the vibrational decays d…
Carboranyl Substituted Siloxanes and Octasilsesquioxanes: Synthesis, Characterization, and Reactivity
2008
Carboranyl-containing disiloxane, cyclic-siloxane and cage-like silsesquioxane have been prepared in high yields. Two routes are compared for their preparation, a classical hydrolytic process based on hydrolysis and condensation of the freshly prepared carboranylalkylchlorosilane and ethoxysilane precursors and a nonhydrolytic route based on the specific reactivity of chorosilane toward DMSO. Based on the typical reactivity of the carboranyl group toward nucleophiles, dianionic disiloxanes and octaanionic silsesquioxanes were obtained without modification of the siloxane bond. Products are fully characterized by FTIR, NMR and MALDI-TOF methods.
Multi-Alkenylsilsesquioxanes as Comonomers and Active Species Modifiers of Metallocene Catalyst in Copolymerization with Ethylene.
2018
The copolymers of ethylene (E) with open-caged iso-butyl-substituted tri-alkenyl-silsesquioxanes (POSS-6-3 and POSS-10-3) and phenyl-substituted tetra-alkenyl-silsesquioxane (POSS-10-4) were synthesized by copolymerization over the ansa-metallocene catalyst. The influence of the kind of silsesquioxane and of the copolymerization conditions on the reaction performance and on the properties of the copolymers was studied. In the case of copolymerization of E/POSS-6-3, the positive comonomer effect was observed, which was associated with the influence of POSS-6-3 on transformation of the bimetallic ion pair to the active catalytic species. Functionality of silsesquioxanes and polymerization par…