Search results for "Silsesquioxane"
showing 10 items of 65 documents
Functionalized siloxane‐silsesquioxane resins and polypropylene‐based composites: Morphological, structural, thermal, and mechanical properties
2018
Non‐functionalized and n‐alkyl‐functionalized siloxane‐silsesquioxane resins (S4SQ) were synthesized and characterized to confirm their structure and properties. Polypropylene (PP) composites with S4SQ resins as fillers were prepared by the melt blending. The influence of the kinds and amounts of fillers on the structural, morphological and thermal properties as well as mechanical characteristics and processability was determined. High compatibility of composites with functionalized resins resulted in more homogenous dispersion of filler particles in comparison with the composites which contained a non‐functionalized resin. Moreover, the introduction of S4SQ resins into PP strongly affected…
Study of thermal properties of polyethylene and polypropylene nanocomposites with long alkyl chain-substituted POSS fillers
2016
The effect of incorporation of octakis({alkyl}dimethylsiloxy)octasilsesquioxanes molecules with n-octyl, n-octadecyl and 4-methyl-hexyl substituents on thermal properties of polypropylene (PP), low-density polyethylene (LDPE) and high-density polyethylene (HDPE) was investigated. Thermal properties of those composite materials were evaluated by means of the differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) methods. The type and mass% content of POSS nanofillers influenced the crystallization and melting properties as well as thermal stability of the obtained polyolefin nanocomposites. The incorporated POSS particles—acting as nucleating agents—improved the crystall…
Investigation of thermal stability of ethylene copolymers with POSS - Study under static and dynamic conditions
2018
Abstract In the paper there was studied thermal stability of a series of ethylene copolymers with monoalkenylsiloxy- or monoalkenylsilsesquioxanes (POSS) under dynamic and static conditions. The copolymers proved to be more thermally stable than neat polyethylene and neat silsesquioxane comonomers. The kind and the content of the POSS units significantly affected degradation of the copolymers. Thermal oxidation process resulted in structural changes of the (co)polymers as it was evidenced by the variations in the kind and content of carbonyl, as well as by unsaturated end groups. Depending on the structure of the POSS comonomer incorporated into the polymer chain, the silsesquioxane units o…
POSS-tetraalkylammonium salts: A new class of ionic liquids
2012
A series of new polyhedral oligomeric silsesquioxane ionic liquids (POSS-ILs) based on the trimethylpropylammonium dielectric constants, which, conversely, display slight differences originating from the nature of the anions. The long alkyl-chain substituents on the POSS core infer on this series of ILs an overall hydrophobic character and solution properties comparable to those of classic cationic surfactants, resulting in an effective extractant capability of polyanions from aqueous solutions. Their solution diffusion properties, as investigated by room-temperature dynamic light scattering, solution conductivity, density, and osmometric measurements, do not provide evidence for the occurr…
Efficient Conversion of Carbon Dioxide by Imidazolium-Based Cross-Linked Nanostructures Containing Polyhedral Oligomeric Silsesquioxane (POSS) Buildi…
2019
Polyhedral oligomeric silsesquioxanes (POSS) have been employed as molecular building blocks for the synthesis of imidazolium cross-linked networks, to be used as heterogeneous catalysts for the conversion of carbon dioxide into cyclic carbonates. Two hybrid materials with different nucleophilic species (bromide and iodide) have been prepared and characterized by means of elemental analysis, 13C and 29Si solid-state NMR spectroscopy, thermogravimetric analysis and IR spectroscopy. The solids were tested as the sole catalyst under metal- and solvent-free reaction conditions showing full selectivity toward the formation of cyclic carbonates. High turnover number (TON) and productivity values,…
Thermal Stability and Flame Retardancy of Polypropylene Composites Containing Siloxane-Silsesquioxane Resins
2018
A novel group of silsesquioxane derivatives, which are siloxane-silsesquioxane resins (S4SQ), was for the first time examined as possible flame retardants in polypropylene (PP) materials. Thermal stability of the PP/S4SQ composites compared to the S4SQ resins and neat PP was estimated using thermogravimetric (TG) analysis under nitrogen and in air atmosphere. The effects of the non-functionalized and n-alkyl-functionalized siloxane-silsesquioxane resins on thermostability and flame retardancy of PP materials were also evaluated by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) and by cone calorimeter tests. The results revealed that the functionalized S4SQ resins may for…
Tri-alkenyl polyhedral oligomeric silsesquioxanes as comonomers and active center modifiers in ethylene copolymerization catalyzed by bis(phenoxy-imi…
2018
Abstract In copolymerization of ethylene (E) with tri-alkenyl-silsesquioxanes (POSS-6-3 and POSS-10-3) were used bis(phenoxy-imine) titanium, zirconium and vanadium catalysts, as well as salen-type vanadium catalysts. There were obtained copolymers with POSS-R-3 units as side branches of polymer chains. The type of employed bis(phenoxy-imine) titanium, zirconium and vanadium catalysts and salen-type catalyst of vanadium determined the copolymer chain termination reactions, as well as the mechanism of modification of the active species by the POSS-R-3 comonomer. POSS-R-3 comonomers caused selective poisoning of bis(phenoxy-imine) zirconium catalyst and they provided protection against tight …
Synthesis, characterization and ethylene polymerization by metallasilsesquioxane
2013
Soluble complexes of group (IV) metallocenes anchored on a substituted polyhedral oligomeric silsesquioxane trisilanol support were prepared and characterized. These catalyst precursors formulated as [M(O^O^O)X] are found to be active in polymerization of ethylene at high temperature in combination with ethylaluminum sesquichloride (Et3Al2Cl3, EASC) as co-catalyst. The polyethylene obtained by these catalysts is linear, crystalline and displays narrow dispersity. The unique low molecular weight PE formed in this reaction exhibits properties comparable to commercial micronized PE waxes that have potential industrial applications in surface coating and ink formulations. Copyright © 2013 John …
POSS nanostructures in catalysis
2020
Polyhedral oligomeric silsesquioxanes (POSS) are organic-inorganic hybrid molecules piquing the interest of researchers thanks to their synergistic features. The great versatility of POSS nanostructures arises from the easy tunability of peripheral organic moieties combined with the high thermal and chemical stability of the inner inorganic core. In this review, we highlight the use of POSS nanostructures as molecular precursors for the synthesis of homogeneous and heterogeneous catalysts able to promote many processes including alkene epoxidation, C-C bond formation, CO2 conversion, "click reactions", hydrogenation, and ethylene polymerisation, among others. In this scenario, POSS units fo…
Synthesis of Defined Poly(silsesquioxane)s: Fast Polycondensation of Trialkoxysilanes in a Continuous-Flow Microreactor
2009
The polycondensation of trialkoxysilanes to PSSQs in a microreactor setup is demonstrated. While continuous-flow processes involving microreactors found various applications in chain growth polymerization, their influence on step-growth polymerization is less explored, and the polycondensation of multifunctional monomers has not been studied in detail. We found significantly increased yields and a decreased polydispersity of the obtained polymers in comparison to the batch process. By variation of the residence time molecular weights could be adjusted reproducibly ranging from M n =1900 to 11000 g · mol -1 . Thus, the microreactor setup offers for the first time the possibility to synthesiz…