Search results for "polymers"
showing 10 items of 3567 documents
Magnetic materials based on coordination chemistry: from switching molecules to multifunctional magnets
2021
Esta tesis tiene como objetivo principal la preparación de materiales moleculares multifuncionales magnéticos. Para ello se han usado dos estrategias diferentes: una aproximación iónica, en la que se han preparado sales de cationes funcionales y se han combinado con redes aniónicas extendidas (capítulos 2 y 3); y la segunda estrategia, donde, a través de enlaces covalentes entre ligandos funcionales y fulerenos (capitulo 4), o polioxometalatos (capítulo 5) se han obtenido sistemas que presentan la propiedad de transición de espín con efectos sinérgicos. En el capítulo 2 se presenta la síntesis y caracterización de varios polímeros de coordinación basados en el ligando anilato con cationes i…
Hybrid magnetic materials based on coordination chemistry: from switching magnetic molecules to 2D coordination polymers
2015
El trabajo descrito en esta tesis se encuadra en el ámbito de los materiales moleculares. Presenta varias estrategias para preparar nuevos materiales híbridos multifuncionales. Los complejos de transición de espín (SCO) constituyen uno de los ejemplos más espectaculares de biestabilidad molecular. En estos sistemas, las transiciones entre los estados de bajo espín (LS) y alto espín (HS) pueden estar inducidos por una variedad de estímulos externos (temperatura, presión o radiación electromagnética). Además de los interesantes aspectos fundamentales, este fenómeno es de interés creciente en el área de los materiales funcionales debido a las posibles aplicaciones en sensores, memorias o dispo…
Copolymerization of Ethylene with Selected Vinyl Monomers Catalyzed by Group 4 Metal and Vanadium Complexes with Multidentate Ligands: A Short Review
2021
This paper gives a short overview of homogeneous post-metallocene catalysts based on group 4 metal and vanadium complexes bearing multidentate ligands. It summarizes the catalytic behavior of those catalysts in copolymerization of ethylene with 1-olefins, with styrenic monomers and with α,ω-alkenols. The review is focused on finding correlations between the structure of a complex, its catalyst activity and comonomer incorporation ability, as well as the microstructure of the copolymer chains.
Growing Like Germany: Local Public Debt, Local Banks, Low Private Investment
2021
The paper uses a panel of more than 1m German firms over 2010-2016, to provide the first firm-bank level evidence of local crowding out for a developed economy characterized by low interest rates and fiscal austerity. Our mechanism relies on two structural features of Germany's banking landscape: the local segmentation of credit markets for small and medium-sized firms (SME) and the role of local public banks in local public finance. Local public banks dominate lending to small and medium firms in Germany and also have an explicit mandate to lend to the local public sector. With spreads on local government debt at all-time lows, local public banks tried to break even, using their market pow…
Ferro- and Antiferromagnetic Interactions in Oxalato-Centered Inverse Hexanuclear and Chain Copper(II) Complexes with Pyrazole Derivatives.
2021
Two novel copper(II) complexes of formulas {[Cu(4-Hmpz)4][Cu(4-Hmpz)2(µ3-ox-κ2O1,O2:κO2′:κO1′)(ClO4)2]}n (1) and {[Cu(3,4,5-Htmpz)4]2[Cu(3,4,5-Htmpz)2(µ3-ox-κ2O1,O2:κO2′:κO1′)(H2O)(ClO4)]2[Cu2(3,4,5-Htmpz)4(µ-ox-κ2O1,O2:κ2O2′,O1′)]}(ClO4)4·6H2O (2) have been obtained by using 4-methyl-1H-pyrazole (4-Hmpz) and 3,4,5-trimethyl-1H-pyrazole (3,4,5-Htmpz) as terminal ligands and oxalate (ox) as the polyatomic inverse coordination center. The crystal structure of 1 consists of perchlorate counteranions and cationic copper(II) chains with alternating bis(pyrazole)(µ3-κ2O1,O2:κO2′:κO1′-oxalato)copper(II) and tetrakis(pyrazole)copper(II) fragments. The crystal structure of 2 is made up of perchlorat…
Synthesis and characterization of ethylene-1-hexene copolymers prepared by using MgCl2(THF)2-supported Ziegler-Natta catalysts
2000
Ethylene was copolymerized with 1-hexene over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated with Et2AlCl. So far these catalyst systems have not been known as initiators of ethylene-1-hexene copolymerization. The vanadium catalysts were more active than the titanium catalyst and, at identical comonomer concentrations in the feed, gave rise to a greater incorporation of 1-hexene into the copolymer. Even at relatively low fractions of 1-hexene, the MgCl2(THF)2-supported catalysts affected much the copolymer properties like density, melting point and crystallinity.
Synthesis and characterization of poly(L,L-lactide)-b-polyethylene glycol) diblock copolymers as plasticizers and their effect on the hydrophilicity …
2011
Polytetrafluoroethylene Films in Rigid Polyurethane Foams' Dielectric Permittivity Measurements with a One-Side Access Capacitive Sensor.
2021
As a non-metallic composite material, widely applied in industry, rigid polyurethane (PUR) foams require knowledge of their dielectric properties. In experimental determination of PUR foams’ dielectric properties protection of one-side capacitive sensor’s active area from adverse effects caused by the PUR foams’ test objects has to be ensured. In the given study, the impact of polytetrafluoroethylene (PTFE) films, thickness 0.20 mm and 0.04 mm, in covering or simulated coating the active area of one-side access capacitive sensor’ electrodes on the experimentally determined true dielectric permittivity spectra of rigid PUR foams is estimated. Penetration depth of the low frequency excitation…