Search results for "polymer chemistry"

Über die Autoxydation ungesättigter Verbindungen VIII. Mitteilung. Eine Methode zur erfassung des anfangsverlaufs der Autoxydation

1959

Es wird eine Methods beschrieben, die den Anfangsverlauf der Autoxydation von substanzen mit niedrigem Dampfdruck (Linolsauremethylester) manometrisch zu verfolgen gestattet. Die Reaktionsgefase sind mit einer Ampullenzertrummerungsvorrichtung ausgestattet, so das die Substanz erst zu einem genau festgelegten Zeitpunkt mit Sauerstoff in Beruhrung gebracht werden kann. Es ist so moglich, die Lolichkeit des Sauerstoffs in der Substanz zu bestimmen. A method is described which measures manometrically the beginning of the autoxidation of substances of low vapour pressure (methyllinoleate). The reaction vessela are fitted out with an equipment to break the ampoules, so that the substance can be …

Kinetics of Zn2+ complexation by a ditopic phenanthroline-azamacrocyclic scorpiand-like receptor.

2012

Coordination of Zn(2+) to a ditopic phenanthroline-macrocycle receptor takes place in three steps, the first one being the coordination to the phenanthroline, followed by the slow movement of the metal to the polyamine macrocycle and a final re-arrangement to coordinate the pendent arm.

Cellulose‑copper as bio-supported recyclable catalyst for the clickable azide-alkyne [3 + 2] cycloaddition reaction in water.

2018

Abstract Naturally-occurring cellulose has been employed as a bio-support macromolecule for the immobilization of either copper(I) or copper(II) ions in order to click azide and alkyne derivatives in water. Under such a click regime, 1,4-disubstitued-1,2,3-triazoles were obtained regioselectively in excellent yields at room temperature. The reaction work-up is simple and the bio-heterogeneous catalyst that has been fully characterized by AAS, SEM, EDX and FT-IR can be easily separated and reused at least five times without any significant decrease in its activity and selectivity, particularly in the case of the very stable CuI-Cellulose.

1994

Liquid crystalline side chain polymers containing photoreactive azobenzene chromophores in the dark-adapted trans form and phenylbenzoate groups as co-mesogens have been prepared and investigated as monomolecular layers at the water/air interface and as multilayer assemblies deposited onto solid supports by the Langmuir–Blodgett–Kuhn (LBK) technique. Pressure area isotherms at variable temperatures together with reflection absorption spectra and Brewster angle microscopic pictures have been taken and analyzed (i) to derive information about the structural order and the packing properties of the mesogenic side groups within the monolayers of different homo- and co-polymeric systems and ii) t…

Fourier-transform infrared study of the switching process in a ferroelectric liquid crystalline polymer

1995

The implementation of the step-scan technique on our spectrometer enabled us to follow the electric field induced reorientation dynamics of different molecular segments of the ferroelectric liquid crystalline polymer [Si(Me)(R)O/Si(Me)(R')O/Si(Me) 2 O] n (R= (CH 2 ) 11 OPhCOOPhOCO * CHCl * CH(Me)(Et); R'= (CH 2 ) 11 OPhN=NPhO * CH(Me)(Hex)) on a sub-millisecond time scale. It was detected that not only the mesogen but also the spacer and at least part of the backbone take part in the reorientation process

Chiral Polyisocyanates from an Azomonomer with a Very High Chiral Induction

2001

The synthesis of new chiral polyisocyanates is described. For this purpose a new chiral azobenzene containing monomer with the chiral center in α-position to the isocyanate group was synthesized. The anionic copolymerization was carried out in THF as solvent with potassium cyanide that was complexed by 18-crown-6 as initiator. This allowed a better control of the reaction and thereby the synthesis of polyisocyanates with a fairly low polydispersity. The copolymers show an extremely high transfer of chirality from the chiral side groups to the helical backbone in dilute solution. Copolymers with only 1.6 mol % of chiral side groups show nearly the full optical rotation and exist predominantl…

Chiral donor–π-acceptor azobenzene dyes

2009

Abstract Four chiral donor–π-acceptor azobenzene dye conjugates were synthesized and characterized. Chiral moieties, namely (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (naproxen) and (S)-2-aminopropionic acid ( l -alanine), were attached to either the donor end or the acceptor site of the azo compound using ester or amide bonds, respectively. The structures of the molecules were verified using 1H NMR, 13C NMR and ESI TOF mass spectrometry; spectral properties were evaluated with UV–vis and CD spectrometry whilst thermal stability was determined by TGA. The compounds displayed a broad absorption maximum in the visible region between 433 and 483 nm. All compounds showed relatively high the…

1986

The terpolymerization of the three monomers (3-vinyl phenylazo)methylmalodinitrile (1), (3-vinyl phenylazo)phenylsulfid (2) or 1-(3-vinylphenylazo)-1,1′-diphenyl methylacetate (3) with methyl methacrylate and butanediol-1,4-dimethyacrylate leads to networks in which the thermolabile azo groups remain intact. Both, the azo monomer and the crosslinking agent are essentially quantitatively incorporated into the network before the conversion of the third monomer is complete. The networks have been characterized in terms of their swelling in benzene, chlorobenzene, and methacrylonitrile. Die Terpolymerisation der drei Monomeren (3-Vinylphenylazo)-methylmalodinitril (1), (3-Vinylphenylazo)phenyls…

Differential branching fractions and isospin asymmetries of B -> K ((*)) μ(+) μ(-) decays

2014

The isospin asymmetries of $B \to K\mu^+\mu^-$ and $B \to K^{*}\mu^+\mu^-$ decays and the partial branching fractions of the $B^0 \to K^0\mu^+\mu^-$, $B^+ \to K^+\mu^+\mu^-$ and $B^+ \to K^{*+}\mu^+\mu^-$ decays are measured as functions of the dimuon mass squared, $q^2$. The data used correspond to an integrated luminosity of 3$~$fb$^{-1}$ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7$\,$TeV and 8$\,$TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions, while individually consistent, all favour lower values than their respective Standard M…

Versuch einer quantitativen endgruppenbestimmung mittels IR-spektren in mit einem diacylperoxyd hergestelltem polystyrol

1962

Ein mit einem Diacylperoxyd der 4-Benzolazo-benzoesaure hergestelltes Polystyrol wird in Fraktionen zerlegt und die Absorptionsbande bei 1724·cm−1 von Losungen in CCl4 nach der Grundlinienmethode ausgewertet. Die Messung der Bande bei 1724·cm−1 von Losungen mit bekannter Konzentration von 4-Benzolazo-benzoesaure-β-phenylathylester in CCl4 gibt eine Eichkurve, mit welcher der Endgruppengehalt in den Polystyrolfraktionen ermittelt wird. Unter bestimmten Voraussetzungen lassen sich aus den Endgruppengehalten Molekulargewichte berechnen, die bis zu etwa 70 000 mit auf anderem Wege ermittelten Molekulargewichten ubereinstimmen. Bei hoheren Molekulargewichten zeigen sich Abweichungen, die erorter…