Search results for "Ethylene"

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

2006

The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L = Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at …

Die kolorimetrische bestimmung höhermolekularer phenol-formaldehyd-kondensate in dimethylformamid-methanol-lösung mit FeCl3

1961

Phenol-Formaldehyd-Kondensate geben in einem Gemisch aus Dimethylformamid und Methanol (4:1, Vol.) mit FeCl3 · 6H2O eine Farbreaktion. Es konnten Bedingungen ausfindig gemacht werden, unter denen die Extinktion der Farbreaktion reproduzierbar und innerhalb der Meszeit konstant ist. Diese Farbreaktion wird von konstitutions- und molekulareinheitlichen Phenol-Formaldehyd-Kondensaten bis zum Molekulargewicht 900 gegeben, selbst wenn sie keine Hydroxymethylgruppen besitzen. Bei der Kondensation von 2,6-Dihydroxymethyl-4-methylphenol zu Polyhydroxydibenzylathern (Molekulargewicht bis 3400) zeigt sich eine charakteristische, hypsochrome Verschiebung des Absorptions maximums, wahrend die sauer erh…

Fast Response Heating Module for Temperature Programmed GC Analysis in Microreaction Systems

2000

For monitoring the reactant and product concentrations of a gas phase microreactor for ethylene oxide synthesis the development of a miniaturised device for fast GC analysis suitable for operation in conjunction with the microreactor is advantageous. Therefore, a method employing short (0.2 – 0.4 m) packed capillary columns was developed. Highly crosslinked polystyrene microspheres proved to be the most suitable adsorbent enabling a high separation efficiency. For fast temperature programming design concepts for an efficient heating module capable to be used with short capillary columns were developed. In principle, planar as well as cylindrical designs are suitable for integration of a res…

Kinetische untersuchungen zur reaktionsfähighkeit von chlormethylgruppen in methylendiphenolen

1984

The chloromethyl derivatives of 16 differently substituted methylenediphenols were synthesized for the first time. To compare their reactivity, the solvolysis in methanol and the animolysis with an excess of p-nitroaniline in dimethyl sulfoxide were studied kinetically at 25°C. The rate constants for the methanolysis do not differ very much, beside of the fact that para-chloromethyl derivatives react about 100 times faster than ortho-chloromethyl derivatives. However, for the aminolysis a large acceleration up to 103 was found for compounds having both hydroxyl groups in ortho-position to the methylene bridge. Obviously, the cleavage of the OH bond, which occurs in the rate determining step…

Der einfluß benachbarter grundbausteine auf die ammonolyse von essigsäureestern phenolischer mehrkernverbindungen

1972

Die Ammonolyse der Essigsaureester verschiedener phenolischer Zwei- und Dreikernverbindungen, die neben Methylphenolbausteinen jeweils einen Nitrophenolbaustein enthalten, wurde untersucht. In allen Fallen wird wie bei einkernigen Nitrophenylestern die Esterbindung im Nitrophenolbaustein ammonolytisch gespalten. Wenn die Bausteine uber Methylenbrucken in ortho-Stellung zu den phenolischen Hydroxylgruppen verknupft sind, werden jedoch auch die Esterbindungen in den Methylphenolbausteinen gespalten, obwohl die Ester von Methylphenolen und Mehrkernverbindungen, die nur Methylgruppen als Substituenten tragen, unter gleichen Bedingungen durch Ammoniak nicht angegriffen werden. In ubereinstimmung…

Effect of filtration conditions on the apparent density of the intercrystalline layers of polyethylene single crystal mats

1969

Organocatalytic α-Methylenation of Aldehydes: Preparation of 3,7-Dimethyl-2-Methylene-6-Octenal

2010

4-(Dimethylamino)benzoic acid Pyrrolidine Citronellal 3,7-Dimethyl-2-methylene-6-octenal Formaldehdye, aqueous Keywords: Aldehydes. Methylenation; Organo catalytic reaction; Alpha-substituted acroleins; Intermediates; Rapid synthesis; Functionalities; Waste disposal

Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions

2002

Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported.

How do different surface modification strategies affect the properties of MnO nanoparticles for biomedical applications? Comparison of PEGylated and …

2011

ABSTRACTMnO nanoparticles (NPs) were surface functionalized by two different approaches, (1) using a dopamine-poly(ethylene glycol) (PEG) (DA-PEG) ligand and (2) by encapsulation within a thin silica shell applying a novel approach. Both MnO@DA-PEG and MnO@SiO2 NPs exhibited excellent long-term stability in physiological solutions. In addition, the cytotoxic potential of both materials was comparatively low. Furthermore, owing to the magnetic properties of MnO NPs, both MnO@DA-PEG and MnO@SiO2 lead to a shortening of the longitudinal relaxation time T1 in MRI. In comparison to the PEGylated MnO NPs, the presence of a thin silica shell led to a greater stability of the MnO core itself by pre…

Fluorescence Probe and Scanning Force Microscopic Studies of Water Soluble Comb-Shaped Copolymers Consisting of a Hydrophobic Poly(p-alkylstyrene) Ma…

2002

Fluorescence Probe and Scanning Force Microscopic Studies of Water Soluble Comb-Shaped Copolymers Consisting of a Hydrophobic Poly( p -alkylstyrene) Main Chainand Hydrophilic Poly(ethylene oxide) Grafted Chains